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{{About||deep versus shallow learning in educational psychology|Student approaches to learning|more information|Artificial neural network}}
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'''Deep learning''' (also known as '''deep structured learning''' or '''differential programming''') is part of a broader family of [[machine learning]] methods based on [[artificial neural networks]] with [[representation learning]]. Learning can be [[Supervised learning|supervised]], [[Semi-supervised learning|semi-supervised]] or [[Unsupervised learning|unsupervised]].<ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="NatureBengio">{{cite journal |last1=Bengio |first1=Yoshua |last2=LeCun |first2= Yann| last3=Hinton | first3= Geoffrey|year=2015 |title=Deep Learning |journal=Nature |volume=521 |issue=7553 |pages=436–444 |doi=10.1038/nature14539 |pmid=26017442|bibcode=2015Natur.521..436L |url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256 }}</ref>


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Deep learning architectures such as [[#Deep_neural_networks|deep neural network]]s, [[deep belief network]]s, [[recurrent neural networks]] and [[convolutional neural networks]] have been applied to fields including [[computer vision]], [[automatic speech recognition|speech recognition]], [[natural language processing]], [[audio recognition]], social network filtering, [[machine translation]], [[bioinformatics]], [[drug design]], medical image analysis, material inspection and [[board game]] programs, where they have produced results comparable to and in some cases surpassing human expert performance.<ref name=":9">{{Cite book |doi=10.1109/cvpr.2012.6248110 |isbn=978-1-4673-1228-8|arxiv=1202.2745|chapter=Multi-column deep neural networks for image classification|title=2012 IEEE Conference on Computer Vision and Pattern Recognition|pages=3642–3649|year=2012|last1=Ciresan|first1=D.|last2=Meier|first2=U.|last3=Schmidhuber|first3=J.}}</ref><ref name="krizhevsky2012">{{cite journal|last1=Krizhevsky|first1=Alex|last2=Sutskever|first2=Ilya|last3=Hinton|first3=Geoffry|date=2012|title=ImageNet Classification with Deep Convolutional Neural Networks|url=https://www.cs.toronto.edu/~kriz/imagenet_classification_with_deep_convolutional.pdf|journal=NIPS 2012: Neural Information Processing Systems, Lake Tahoe, Nevada}}
</ref><ref>{{cite web |title=Google's AlphaGo AI wins three-match series against the world's best Go player |url=https://techcrunch.com/2017/05/24/alphago-beats-planets-best-human-go-player-ke-jie/amp/ |website=TechCrunch |date=25 May 2017}}</ref>


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[[Artificial neural network]]s (ANNs) were inspired by information processing and distributed communication nodes in biological systems. ANNs have various differences from biological [[brain]]s. Specifically, neural networks tend to be static and symbolic, while the biological brain of most living organisms is dynamic (plastic) and analog.<ref>{{Cite journal|last=Marblestone|first=Adam H.|last2=Wayne|first2=Greg|last3=Kording|first3=Konrad P.|date=2016|title=Toward an Integration of Deep Learning and Neuroscience |journal=Frontiers in Computational Neuroscience |volume=10|pages=94|doi=10.3389/fncom.2016.00094 |pmc=5021692|pmid=27683554|bibcode=2016arXiv160603813M|arxiv=1606.03813|url=https://www.semanticscholar.org/paper/2dec4f52b1ce552b416f086d4ea1040626675dfa}}</ref><ref>{{cite journal|last1=Olshausen|first1=B. A.|year=1996|title=Emergence of simple-cell receptive field properties by learning a sparse code for natural images|journal=Nature|volume=381|issue=6583|pages=607–609|bibcode=1996Natur.381..607O|doi=10.1038/381607a0|pmid=8637596|url=https://www.semanticscholar.org/paper/8012c4a1e2ca663f1a04e80cbb19631a00cbab27}}</ref><ref>{{cite arxiv|last=Bengio|first=Yoshua|last2=Lee|first2=Dong-Hyun|last3=Bornschein|first3=Jorg|last4=Mesnard|first4=Thomas|last5=Lin|first5=Zhouhan|date=2015-02-13|title=Towards Biologically Plausible Deep Learning|eprint=1502.04156|class=cs.LG}}</ref>
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== Definition ==
[[File:Deep Learning.jpg|alt=Representing Images on Multiple Layers of Abstraction in Deep Learning|thumb|Representing Images on Multiple Layers of Abstraction in Deep Learning <ref>{{Cite journal|last=Schulz|first=Hannes|last2=Behnke|first2=Sven|date=2012-11-01|title=Deep Learning|journal=KI - Künstliche Intelligenz|language=en|volume=26|issue=4|pages=357–363|doi=10.1007/s13218-012-0198-z|issn=1610-1987|url=https://www.semanticscholar.org/paper/51a80649d16a38d41dbd20472deb3bc9b61b59a0}}</ref>]]
Deep learning is a class of [[machine learning]] [[algorithm]]s that<ref name="BOOK2014">{{cite journal|last2=Yu|first2=D.|year=2014|title=Deep Learning: Methods and Applications|url=http://research.microsoft.com/pubs/209355/DeepLearning-NowPublishing-Vol7-SIG-039.pdf|journal=Foundations and Trends in Signal Processing|volume=7|issue=3–4|pages=1–199|doi=10.1561/2000000039|last1=Deng|first1=L.}}</ref>{{rp|pages=199–200}} uses multiple layers to progressively extract higher level features from the raw input. For example, in [[image processing]], lower layers may identify edges, while higher layers may identify the concepts relevant to a human such as digits or letters or faces.

== Overview ==
Most modern deep learning models are based on artificial neural networks, specifically, [[Convolutional Neural Network]]s (CNN)s, although they can also include [[propositional formula]]s or latent variables organized layer-wise in deep [[generative model]]s such as the nodes in [[deep belief network]]s and deep [[Boltzmann machine]]s.<ref name="BENGIODEEP">{{cite journal|last=Bengio|first=Yoshua|year=2009|title=Learning Deep Architectures for AI|url=http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20%282009%29.pdf|journal=Foundations and Trends in Machine Learning|volume=2|issue=1|pages=1–127|doi=10.1561/2200000006|citeseerx=10.1.1.701.9550|access-date=2015-09-03|archive-url=https://web.archive.org/web/20160304084250/http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20(2009).pdf|archive-date=2016-03-04|url-status=dead}}</ref>

In deep learning, each level learns to transform its input data into a slightly more abstract and composite representation. In an image recognition application, the raw input may be a [[Matrix (mathematics)|matrix]] of pixels; the first representational layer may abstract the pixels and encode edges; the second layer may compose and encode arrangements of edges; the third layer may encode a nose and eyes; and the fourth layer may recognize that the image contains a face. Importantly, a deep learning process can learn which features to optimally place in which level ''on its own''. (Of course, this does not completely eliminate the need for hand-tuning; for example, varying numbers of layers and layer sizes can provide different degrees of abstraction.)<ref name="BENGIO2012">{{cite journal|last2=Courville|first2=A.|last3=Vincent|first3=P.|year=2013|title=Representation Learning: A Review and New Perspectives|journal=IEEE Transactions on Pattern Analysis and Machine Intelligence|volume=35|issue=8|pages=1798–1828|arxiv=1206.5538|doi=10.1109/tpami.2013.50|pmid=23787338|last1=Bengio|first1=Y.}}</ref><ref>{{cite journal|last1=LeCun|first1=Yann|last2=Bengio|first2=Yoshua|last3=Hinton|first3=Geoffrey|title=Deep learning|journal=Nature|date=28 May 2015|volume=521|issue=7553|pages=436–444|doi=10.1038/nature14539|pmid=26017442|bibcode=2015Natur.521..436L|url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256}}</ref>

The word "deep" in "deep learning" refers to the number of layers through which the data is transformed. More precisely, deep learning systems have a substantial ''credit assignment path'' (CAP) depth. The CAP is the chain of transformations from input to output. CAPs describe potentially causal connections between input and output. For a [[feedforward neural network]], the depth of the CAPs is that of the network and is the number of hidden layers plus one (as the output layer is also parameterized). For [[recurrent neural network]]s, in which a signal may propagate through a layer more than once, the CAP depth is potentially unlimited.<ref name="SCHIDHUB" /> No universally agreed upon threshold of depth divides shallow learning from deep learning, but most researchers agree that deep learning involves CAP depth higher than 2. CAP of depth 2 has been shown to be a universal approximator in the sense that it can emulate any function.<ref>{{Cite book|url=https://books.google.com/books?id=9CqQDwAAQBAJ&pg=PA15&dq#v=onepage&q&f=false|title=Human Behavior and Another Kind in Consciousness: Emerging Research and Opportunities: Emerging Research and Opportunities|last=Shigeki|first=Sugiyama|date=2019-04-12|publisher=IGI Global|isbn=978-1-5225-8218-2|language=en}}</ref> Beyond that, more layers do not add to the function approximator ability of the network. Deep models (CAP > 2) are able to extract better features than shallow models and hence, extra layers help in learning the features effectively.

Deep learning architectures can be constructed with a [[greedy algorithm|greedy]] layer-by-layer method.<ref name=BENGIO2007>{{cite conference | first1=Yoshua | last1=Bengio | first2=Pascal | last2=Lamblin | first3=Dan|last3=Popovici |first4=Hugo|last4=Larochelle | title=Greedy layer-wise training of deep networks| year=2007 | url=http://papers.nips.cc/paper/3048-greedy-layer-wise-training-of-deep-networks.pdf| conference = Advances in neural information processing systems | pages= 153–160}}</ref> Deep learning helps to disentangle these abstractions and pick out which features improve performance.<ref name="BENGIO2012" />

For [[supervised learning]] tasks, deep learning methods eliminate [[feature engineering]], by translating the data into compact intermediate representations akin to [[Principal Component Analysis|principal components]], and derive layered structures that remove redundancy in representation.

Deep learning algorithms can be applied to unsupervised learning tasks. This is an important benefit because unlabeled data are more abundant than the labeled data. Examples of deep structures that can be trained in an unsupervised manner are neural history compressors<ref name="scholarpedia">Jürgen Schmidhuber (2015). Deep Learning. Scholarpedia, 10(11):32832. [http://www.scholarpedia.org/article/Deep_Learning Online]</ref> and [[deep belief network]]s.<ref name="BENGIO2012" /><ref name="SCHOLARDBNS">{{cite journal | last1 = Hinton | first1 = G.E. | year = 2009| title = Deep belief networks | url= | journal = Scholarpedia | volume = 4 | issue = 5| page = 5947 | doi=10.4249/scholarpedia.5947| bibcode = 2009SchpJ...4.5947H}}</ref>

== Interpretations ==
Deep neural networks are generally interpreted in terms of the [[universal approximation theorem]]<ref name="ReferenceB">Balázs Csanád Csáji (2001). Approximation with Artificial Neural Networks; Faculty of Sciences; Eötvös Loránd University, Hungary</ref><ref name=cyb>{{cite journal | last1 = Cybenko | year = 1989 | title = Approximations by superpositions of sigmoidal functions | url = http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | journal = [[Mathematics of Control, Signals, and Systems]] | volume = 2 | issue = 4 | pages = 303–314 | doi = 10.1007/bf02551274 | url-status = dead | archiveurl = https://web.archive.org/web/20151010204407/http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | archivedate = 2015-10-10 }}</ref><ref name=horn>{{cite journal | last1 = Hornik | first1 = Kurt | year = 1991 | title = Approximation Capabilities of Multilayer Feedforward Networks | url= | journal = Neural Networks | volume = 4 | issue = 2| pages = 251–257 | doi=10.1016/0893-6080(91)90009-t}}</ref><ref name="Haykin, Simon 1998">{{cite book|first=Simon S. |last=Haykin|title=Neural Networks: A Comprehensive Foundation|url={{google books |plainurl=y |id=bX4pAQAAMAAJ}}|year=1999|publisher=Prentice Hall|isbn=978-0-13-273350-2}}</ref><ref name="Hassoun, M. 1995 p. 48">{{cite book|first=Mohamad H. |last=Hassoun|title=Fundamentals of Artificial Neural Networks|url={{google books |plainurl=y |id=Otk32Y3QkxQC|page=48}}|year=1995|publisher=MIT Press|isbn=978-0-262-08239-6|p=48}}</ref><ref name=ZhouLu>Lu, Z., Pu, H., Wang, F., Hu, Z., & Wang, L. (2017). [http://papers.nips.cc/paper/7203-the-expressive-power-of-neural-networks-a-view-from-the-width The Expressive Power of Neural Networks: A View from the Width]. Neural Information Processing Systems, 6231-6239.
</ref> or [[Bayesian inference|probabilistic inference]].<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB">{{cite journal|last=Schmidhuber|first=J.|year=2015|title=Deep Learning in Neural Networks: An Overview|journal=Neural Networks|volume=61|pages=85–117|arxiv=1404.7828|doi=10.1016/j.neunet.2014.09.003|pmid=25462637|url=https://www.semanticscholar.org/paper/126df9f24e29feee6e49e135da102fbbd9154a48}}</ref><ref name="SCHOLARDBNS" /><ref name = MURPHY>{{cite book|first=Kevin P. |last=Murphy|title=Machine Learning: A Probabilistic Perspective|url={{google books |plainurl=y |id=NZP6AQAAQBAJ}}|date=24 August 2012|publisher=MIT Press|isbn=978-0-262-01802-9}}</ref><ref name= "Patel NIPS 2016">{{Cite journal|url=https://papers.nips.cc/paper/6231-a-probabilistic-framework-for-deep-learning.pdf|title=A Probabilistic Framework for Deep Learning|last=Patel|first=Ankit|last2=Nguyen|first2=Tan|last3=Baraniuk|first3=Richard|date=2016|journal=Advances in Neural Information Processing Systems|pages=|bibcode=2016arXiv161201936P|arxiv=1612.01936}}</ref>

The classic universal approximation theorem concerns the capacity of [[feedforward neural networks]] with a single hidden layer of finite size to approximate [[continuous functions]].<ref name="ReferenceB"/><ref name="cyb"/><ref name="horn"/><ref name="Haykin, Simon 1998"/><ref name="Hassoun, M. 1995 p. 48"/> In 1989, the first proof was published by [[George Cybenko]] for [[sigmoid function|sigmoid]] activation functions<ref name="cyb" /> and was generalised to feed-forward multi-layer architectures in 1991 by Kurt Hornik.<ref name="horn" /> Recent work also showed that universal approximation also holds for non-bounded activation functions such as the rectified linear unit.<ref name=sonoda17>{{cite journal | last1 = Sonoda | first1 = Sho | last2=Murata | first2=Noboru | year = 2017 | title = Neural network with unbounded activation functions is universal approximator | journal = Applied and Computational Harmonic Analysis | volume = 43 | issue = 2 | pages = 233–268 | doi = 10.1016/j.acha.2015.12.005| arxiv = 1505.03654 | url = https://www.semanticscholar.org/paper/d0e48a4d5d6d0b4aa2dbab2c50560945e62a3817 }}</ref>

The universal approximation theorem for [[deep neural network]]s concerns the capacity of networks with bounded width but the depth is allowed to grow. Lu et al.<ref name=ZhouLu/> proved that if the width of a [[deep neural network]] with [[ReLU]] activation is strictly larger than the input dimension, then the network can approximate any [[Lebesgue integration|Lebesgue integrable function]]; If the width is smaller or equal to the input dimension, then [[deep neural network]] is not a universal approximator.

The [[probabilistic]] interpretation<ref name="MURPHY" /> derives from the field of [[machine learning]]. It features inference,<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="SCHOLARDBNS" /><ref name="MURPHY" /> as well as the [[optimization]] concepts of [[training]] and [[test (assessment)|testing]], related to fitting and [[generalization]], respectively. More specifically, the probabilistic interpretation considers the activation nonlinearity as a [[cumulative distribution function]].<ref name="MURPHY" /> The probabilistic interpretation led to the introduction of [[dropout (neural networks)|dropout]] as [[Regularization (mathematics)|regularizer]] in neural networks.<ref name="DROPOUT">{{cite arXiv |last1=Hinton |first1=G. E. |last2=Srivastava| first2 =N.|last3=Krizhevsky| first3=A.| last4 =Sutskever| first4=I.| last5=Salakhutdinov| first5=R.R.|eprint=1207.0580 |class=math.LG |title=Improving neural networks by preventing co-adaptation of feature detectors |date=2012}}</ref> The probabilistic interpretation was introduced by researchers including [[John Hopfield|Hopfield]], [[Bernard Widrow|Widrow]] and [[Kumpati S. Narendra|Narendra]] and popularized in surveys such as the one by [[Christopher Bishop|Bishop]].<ref name="prml">{{cite book|title=Pattern Recognition and Machine Learning|author=Bishop, Christopher M.|year=2006|publisher=Springer|url=http://users.isr.ist.utl.pt/~wurmd/Livros/school/Bishop%20-%20Pattern%20Recognition%20And%20Machine%20Learning%20-%20Springer%20%202006.pdf|isbn=978-0-387-31073-2}}</ref>

== History ==
The term ''Deep Learning'' was introduced to the machine learning community by [[Rina Dechter]] in 1986,<ref name="dechter1986">[[Rina Dechter]] (1986). Learning while searching in constraint-satisfaction problems. University of California, Computer Science Department, Cognitive Systems Laboratory.[https://www.researchgate.net/publication/221605378_Learning_While_Searching_in_Constraint-Satisfaction-Problems Online]</ref><ref name="scholarpedia" /> and to [[Artificial Neural Networks|artificial neural networks]] by Igor Aizenberg and colleagues in 2000, in the context of [[Boolean network|Boolean]] threshold neurons.<ref name="aizenberg2000">Igor Aizenberg, Naum N. Aizenberg, Joos P.L. Vandewalle (2000). Multi-Valued and Universal Binary Neurons: Theory, Learning and Applications. Springer Science & Business Media.</ref><ref>Co-evolving recurrent neurons learn deep memory POMDPs. Proc. GECCO, Washington, D. C., pp. 1795-1802, ACM Press, New York, NY, USA, 2005.</ref>

The first general, working learning algorithm for supervised, deep, feedforward, multilayer [[perceptron]]s was published by [[Alexey Ivakhnenko]] and Lapa in 1967.<ref name="ivak1965">{{cite book|first1=A. G. |last1=Ivakhnenko |first2=V. G. |last2=Lapa |title=Cybernetics and Forecasting Techniques|url={{google books |plainurl=y |id=rGFgAAAAMAAJ}}|year=1967|publisher=American Elsevier Publishing Co.|isbn=978-0-444-00020-0}}</ref> A 1971 paper described already a deep network with 8 layers trained by the [[group method of data handling]] algorithm.<ref name="ivak1971">{{Cite journal|last=Ivakhnenko|first=Alexey|date=1971|title=Polynomial theory of complex systems|url=http://gmdh.net/articles/history/polynomial.pdf |journal=IEEE Transactions on Systems, Man and Cybernetics |pages=364–378|doi=10.1109/TSMC.1971.4308320|pmid=|accessdate=|volume=SMC-1|issue=4}}</ref>

Other deep learning working architectures, specifically those built for [[computer vision]], began with the [[Neocognitron]] introduced by [[Kunihiko Fukushima]] in 1980.<ref name="FUKU1980">{{cite journal | last1 = Fukushima | first1 = K. | year = 1980 | title = Neocognitron: A self-organizing neural network model for a mechanism of pattern recognition unaffected by shift in position | url= | journal = Biol. Cybern. | volume = 36 | issue = 4| pages = 193–202 | doi=10.1007/bf00344251 | pmid=7370364}}</ref> In 1989, [[Yann LeCun]] et al. applied the standard backpropagation algorithm, which had been around as the reverse mode of [[automatic differentiation]] since 1970,<ref name="lin1970">[[Seppo Linnainmaa]] (1970). The representation of the cumulative rounding error of an algorithm as a Taylor expansion of the local rounding errors. Master's Thesis (in Finnish), Univ. Helsinki, 6-7.</ref><ref name="grie2012">{{Cite journal|last=Griewank|first=Andreas|date=2012|title=Who Invented the Reverse Mode of Differentiation?|url=http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|journal=Documenta Mathematica|issue=Extra Volume ISMP|pages=389–400|access-date=2017-06-11|archive-url=https://web.archive.org/web/20170721211929/http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|archive-date=2017-07-21|url-status=dead}}</ref><ref name="WERBOS1974">{{Cite journal|last=Werbos|first=P.|date=1974|title=Beyond Regression: New Tools for Prediction and Analysis in the Behavioral Sciences |url=https://www.researchgate.net/publication/35657389 |journal=Harvard University |accessdate=12 June 2017}}</ref><ref name="werbos1982">{{Cite book|chapter-url=ftp://ftp.idsia.ch/pub/juergen/habilitation.pdf|title=System modeling and optimization|last=Werbos|first=Paul|publisher=Springer|year=1982|isbn=|location=|pages=762–770|chapter=Applications of advances in nonlinear sensitivity analysis}}</ref> to a deep neural network with the purpose of recognizing handwritten [[ZIP code]]s on mail. While the algorithm worked, training required 3 days.<ref name="LECUN1989">LeCun ''et al.'', "Backpropagation Applied to Handwritten Zip Code Recognition," ''Neural Computation'', 1, pp. 541–551, 1989.</ref>

By 1991 such systems were used for recognizing isolated 2-D hand-written digits, while [[3D object recognition|recognizing 3-D objects]] was done by matching 2-D images with a handcrafted 3-D object model. Weng ''et al.'' suggested that a human brain does not use a monolithic 3-D object model and in 1992 they published Cresceptron,<ref name="Weng1992">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCNN1992.pdf Cresceptron: a self-organizing neural network which grows adaptively]," ''Proc. International Joint Conference on Neural Networks'', Baltimore, Maryland, vol I, pp. 576-581, June, 1992.</ref><ref name="Weng1993">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronICCV1993.pdf Learning recognition and segmentation of 3-D objects from 2-D images]," ''Proc. 4th International Conf. Computer Vision'', Berlin, Germany, pp. 121-128, May, 1993.</ref><ref name="Weng1997">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCV.pdf Learning recognition and segmentation using the Cresceptron]," ''International Journal of Computer Vision'', vol. 25, no. 2, pp. 105-139, Nov. 1997.</ref> a method for performing 3-D object recognition in cluttered scenes. Because it directly used natural images, Cresceptron started the beginning of general-purpose visual learning for natural 3D worlds. Cresceptron is a cascade of layers similar to Neocognitron. But while Neocognitron required a human programmer to hand-merge features, Cresceptron learned an open number of features in each layer without supervision, where each feature is represented by a [[Convolution|convolution kernel]]. Cresceptron segmented each learned object from a cluttered scene through back-analysis through the network. [[Max pooling]], now often adopted by deep neural networks (e.g. [[ImageNet]] tests), was first used in Cresceptron to reduce the position resolution by a factor of (2x2) to 1 through the cascade for better generalization.

In 1994, André de Carvalho, together with Mike Fairhurst and David Bisset, published experimental results of a multi-layer boolean neural network, also known as a weightless neural network, composed of a 3-layers self-organising feature extraction neural network module (SOFT) followed by a multi-layer classification neural network module (GSN), which were independently trained. Each layer in the feature extraction module extracted features with growing complexity regarding the previous layer.<ref>{{Cite journal |title=An integrated Boolean neural network for pattern classification |journal=Pattern Recognition Letters |date=1994-08-08 |pages=807–813 |volume=15 |issue=8 |doi=10.1016/0167-8655(94)90009-4 |first=Andre C. L. F. |last1=de Carvalho |first2 = Mike C. |last2=Fairhurst |first3=David |last3 = Bisset}}</ref>

In 1995, [[Brendan Frey]] demonstrated that it was possible to train (over two days) a network containing six fully connected layers and several hundred hidden units using the [[wake-sleep algorithm]], co-developed with [[Peter Dayan]] and [[Geoffrey Hinton|Hinton]].<ref>{{Cite journal|title = The wake-sleep algorithm for unsupervised neural networks |journal = Science|date = 1995-05-26|pages = 1158–1161|volume = 268|issue = 5214|doi = 10.1126/science.7761831|pmid = 7761831|first = Geoffrey E.|last = Hinton|first2 = Peter|last2 = Dayan|first3 = Brendan J.|last3 = Frey|first4 = Radford|last4 = Neal|bibcode = 1995Sci...268.1158H}}</ref> Many factors contribute to the slow speed, including the [[vanishing gradient problem]] analyzed in 1991 by [[Sepp Hochreiter]].<ref name="HOCH1991">S. Hochreiter., "[http://people.idsia.ch/~juergen/SeppHochreiter1991ThesisAdvisorSchmidhuber.pdf Untersuchungen zu dynamischen neuronalen Netzen]," ''Diploma thesis. Institut f. Informatik, Technische Univ. Munich. Advisor: J. Schmidhuber'', 1991.</ref><ref name="HOCH2001">{{cite book|chapter-url={{google books |plainurl=y |id=NWOcMVA64aAC}}|title=A Field Guide to Dynamical Recurrent Networks|last=Hochreiter|first=S.|display-authors=etal|date=15 January 2001|publisher=John Wiley & Sons|isbn=978-0-7803-5369-5|location=|pages=|chapter=Gradient flow in recurrent nets: the difficulty of learning long-term dependencies|editor-last2=Kremer|editor-first2=Stefan C.|editor-first1=John F.|editor-last1=Kolen}}</ref>

Simpler models that use task-specific handcrafted features such as [[Gabor filter]]s and [[support vector machine]]s (SVMs) were a popular choice in the 1990s and 2000s, because of [[artificial neural network]]'s (ANN) computational cost and a lack of understanding of how the brain wires its biological networks.

Both shallow and deep learning (e.g., recurrent nets) of ANNs have been explored for many years.<ref>{{Cite journal|last=Morgan|first=Nelson|last2=Bourlard |first2=Hervé |last3=Renals |first3=Steve |last4=Cohen |first4=Michael|last5=Franco |first5=Horacio |date=1993-08-01 |title=Hybrid neural network/hidden markov model systems for continuous speech recognition |journal=International Journal of Pattern Recognition and Artificial Intelligence|volume=07|issue=4|pages=899–916|doi=10.1142/s0218001493000455|issn=0218-0014}}</ref><ref name="Robinson1992">{{Cite journal|last=Robinson|first=T.|authorlink=Tony Robinson (speech recognition)|date=1992|title=A real-time recurrent error propagation network word recognition system|url=http://dl.acm.org/citation.cfm?id=1895720|journal=ICASSP|pages=617–620|via=|isbn=9780780305328|series=Icassp'92}}</ref><ref>{{Cite journal|last=Waibel|first=A.|last2=Hanazawa|first2=T.|last3=Hinton|first3=G.|last4=Shikano|first4=K.|last5=Lang|first5=K. J.|date=March 1989|title=Phoneme recognition using time-delay neural networks|journal=IEEE Transactions on Acoustics, Speech, and Signal Processing|volume=37|issue=3|pages=328–339|doi=10.1109/29.21701|issn=0096-3518|hdl=10338.dmlcz/135496|url=http://dml.cz/bitstream/handle/10338.dmlcz/135496/Kybernetika_38-2002-6_2.pdf}}</ref> These methods never outperformed non-uniform internal-handcrafting Gaussian [[mixture model]]/[[Hidden Markov model]] (GMM-HMM) technology based on generative models of speech trained discriminatively.<ref name="Baker2009">{{cite journal | last1 = Baker | first1 = J. | last2 = Deng | first2 = Li | last3 = Glass | first3 = Jim | last4 = Khudanpur | first4 = S. | last5 = Lee | first5 = C.-H. | last6 = Morgan | first6 = N. | last7 = O'Shaughnessy | first7 = D. | year = 2009 | title = Research Developments and Directions in Speech Recognition and Understanding, Part 1 | url= | journal = IEEE Signal Processing Magazine | volume = 26 | issue = 3| pages = 75–80 | doi=10.1109/msp.2009.932166| bibcode = 2009ISPM...26...75B }}</ref> Key difficulties have been analyzed, including gradient diminishing<ref name="HOCH1991" /> and weak temporal correlation structure in neural predictive models.<ref name="Bengio1991">{{Cite web|url=https://www.researchgate.net/publication/41229141|title=Artificial Neural Networks and their Application to Speech/Sequence Recognition|last=Bengio|first=Y.|date=1991|website=|publisher=McGill University Ph.D. thesis|accessdate=}}</ref><ref name="Deng1994">{{cite journal | last1 = Deng | first1 = L. | last2 = Hassanein | first2 = K. | last3 = Elmasry | first3 = M. | year = 1994 | title = Analysis of correlation structure for a neural predictive model with applications to speech recognition | url= | journal = Neural Networks | volume = 7 | issue = 2| pages = 331–339 | doi=10.1016/0893-6080(94)90027-2}}</ref> Additional difficulties were the lack of training data and limited computing power.

Most [[speech recognition]] researchers moved away from neural nets to pursue generative modeling. An exception was at [[SRI International]] in the late 1990s. Funded by the US government's [[National Security Agency|NSA]] and [[DARPA]], SRI studied deep neural networks in speech and speaker recognition. The speaker recognition team led by [[Larry Heck]] reported significant success with deep neural networks in speech processing in the 1998 [[National Institute of Standards and Technology]] Speaker Recognition evaluation.<ref name="Doddington2000">{{cite journal | last1 = Doddington | first1 = G. | last2 = Przybocki | first2 = M. | last3 = Martin | first3 = A. | last4 = Reynolds | first4 = D. | year = 2000 | title = The NIST speaker recognition evaluation ± Overview, methodology, systems, results, perspective | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 225–254 | doi=10.1016/S0167-6393(99)00080-1}}</ref> The SRI deep neural network was then deployed in the Nuance Verifier, representing the first major industrial application of deep learning.<ref name="Heck2000">{{cite journal | last1 = Heck | first1 = L. | last2 = Konig | first2 = Y. | last3 = Sonmez | first3 = M. | last4 = Weintraub | first4 = M. | year = 2000 | title = Robustness to Telephone Handset Distortion in Speaker Recognition by Discriminative Feature Design | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 181–192 | doi=10.1016/s0167-6393(99)00077-1}}</ref>

The principle of elevating "raw" features over hand-crafted optimization was first explored successfully in the architecture of deep autoencoder on the "raw" spectrogram or linear filter-bank features in the late 1990s,<ref name="Heck2000" /> showing its superiority over the Mel-Cepstral features that contain stages of fixed transformation from spectrograms. The raw features of speech, [[waveform]]s, later produced excellent larger-scale results.<ref>{{Cite web|url=https://www.researchgate.net/publication/266030526|title=Acoustic Modeling with Deep Neural Networks Using Raw Time Signal for LVCSR (PDF Download Available)|website=ResearchGate|accessdate=2017-06-14}}</ref>

Many aspects of speech recognition were taken over by a deep learning method called [[long short-term memory]] (LSTM), a recurrent neural network published by Hochreiter and [[Jürgen Schmidhuber|Schmidhuber]] in 1997.<ref name=":0">{{Cite journal|last=Hochreiter|first=Sepp|last2=Schmidhuber|first2=Jürgen|date=1997-11-01|title=Long Short-Term Memory|journal=Neural Computation|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|issn=0899-7667|pmid=9377276|url=https://www.semanticscholar.org/paper/44d2abe2175df8153f465f6c39b68b76a0d40ab9}}</ref> LSTM RNNs avoid the vanishing gradient problem and can learn "Very Deep Learning" tasks<ref name="SCHIDHUB" /> that require memories of events that happened thousands of discrete time steps before, which is important for speech. In 2003, LSTM started to become competitive with traditional speech recognizers on certain tasks.<ref name="graves2003">{{Cite web|url=Ftp://ftp.idsia.ch/pub/juergen/bioadit2004.pdf|title=Biologically Plausible Speech Recognition with LSTM Neural Nets|last=Graves|first=Alex|last2=Eck|first2=Douglas|date=2003|website=1st Intl. Workshop on Biologically Inspired Approaches to Advanced Information Technology, Bio-ADIT 2004, Lausanne, Switzerland|pages=175–184|last3=Beringer|first3=Nicole|last4=Schmidhuber|first4=Jürgen}}</ref> Later it was combined with connectionist temporal classification (CTC)<ref name=":1">{{Cite journal|last=Graves|first=Alex|last2=Fernández|first2=Santiago|last3=Gomez|first3=Faustino|date=2006|title=Connectionist temporal classification: Labelling unsegmented sequence data with recurrent neural networks|journal=Proceedings of the International Conference on Machine Learning, ICML 2006|pages=369–376|citeseerx=10.1.1.75.6306}}</ref> in stacks of LSTM RNNs.<ref name="fernandez2007keyword">Santiago Fernandez, Alex Graves, and Jürgen Schmidhuber (2007). [https://mediatum.ub.tum.de/doc/1289941/file.pdf An application of recurrent neural networks to discriminative keyword spotting]. Proceedings of ICANN (2), pp. 220–229.</ref> In 2015, Google's speech recognition reportedly experienced a dramatic performance jump of 49% through CTC-trained LSTM, which they made available through [[Google Voice Search]].<ref name="sak2015">{{Cite web|url=http://googleresearch.blogspot.ch/2015/09/google-voice-search-faster-and-more.html|title=Google voice search: faster and more accurate|last=Sak|first=Haşim|last2=Senior|first2=Andrew|date=September 2015|website=|accessdate=|last3=Rao|first3=Kanishka|last4=Beaufays|first4=Françoise|last5=Schalkwyk|first5=Johan}}</ref>

In 2006, publications by [[Geoffrey Hinton|Geoff Hinton]], [[Russ Salakhutdinov|Ruslan Salakhutdinov]], Osindero and [[Yee Whye Teh|Teh]]<ref>{{Cite journal|last=Hinton|first=Geoffrey E.|date=2007-10-01|title=Learning multiple layers of representation|url=http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(07)00217-3|journal=Trends in Cognitive Sciences|volume=11|issue=10|pages=428–434|doi=10.1016/j.tics.2007.09.004|issn=1364-6613|pmid=17921042}}</ref>
<ref name=hinton06>{{Cite journal | last1 = Hinton | first1 = G. E. |authorlink1=Geoff Hinton| last2 = Osindero | first2 = S. | last3 = Teh | first3 = Y. W. | doi = 10.1162/neco.2006.18.7.1527 | title = A Fast Learning Algorithm for Deep Belief Nets | journal = [[Neural Computation (journal)|Neural Computation]]| volume = 18 | issue = 7 | pages = 1527–1554 | year = 2006 | pmid = 16764513| pmc = | url = http://www.cs.toronto.edu/~hinton/absps/fastnc.pdf}}</ref><ref name=bengio2012>{{cite arXiv |last=Bengio |first=Yoshua |author-link=Yoshua Bengio |eprint=1206.5533 |title=Practical recommendations for gradient-based training of deep architectures |class=cs.LG|year=2012 }}</ref> showed how a many-layered [[feedforward neural network]] could be effectively pre-trained one layer at a time, treating each layer in turn as an unsupervised [[restricted Boltzmann machine]], then fine-tuning it using supervised [[backpropagation]].<ref name="HINTON2007">G. E. Hinton., "[http://www.csri.utoronto.ca/~hinton/absps/ticsdraft.pdf Learning multiple layers of representation]," ''Trends in Cognitive Sciences'', 11, pp. 428–434, 2007.</ref> The papers referred to ''learning'' for ''deep belief nets.''

Deep learning is part of state-of-the-art systems in various disciplines, particularly computer vision and [[automatic speech recognition]] (ASR). Results on commonly used evaluation sets such as [[TIMIT]] (ASR) and [[MNIST database|MNIST]] ([[image classification]]), as well as a range of large-vocabulary speech recognition tasks have steadily improved.<ref name="HintonDengYu2012" /><ref>{{cite journal|url=https://www.microsoft.com/en-us/research/publication/new-types-of-deep-neural-network-learning-for-speech-recognition-and-related-applications-an-overview/|title=New types of deep neural network learning for speech recognition and related applications: An overview|journal=Microsoft Research|first1=Li|last1=Deng|first2=Geoffrey|last2=Hinton|first3=Brian|last3=Kingsbury|date=1 May 2013|via=research.microsoft.com|citeseerx=10.1.1.368.1123}}</ref><ref>{{Cite book |doi=10.1109/icassp.2013.6639345|isbn=978-1-4799-0356-6|chapter=Recent advances in deep learning for speech research at Microsoft|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8604–8608|year=2013|last1=Deng|first1=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Michael|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|last10=Williams|first10=Jason|last11=Gong|first11=Yifan|last12=Acero|first12=Alex}}</ref> [[Convolutional neural network]]s (CNNs) were superseded for ASR by CTC<ref name=":1" /> for LSTM.<ref name=":0" /><ref name="sak2015" /><ref name="sak2014">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|title=Long Short-Term Memory recurrent neural network architectures for large scale acoustic modeling|last=Sak|first=Hasim|last2=Senior|first2=Andrew|date=2014|website=|accessdate=|last3=Beaufays|first3=Francoise|archive-url=https://web.archive.org/web/20180424203806/https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|archive-date=2018-04-24|url-status=dead}}</ref><ref name="liwu2015">{{cite arxiv |eprint=1410.4281|last1=Li|first1=Xiangang|title=Constructing Long Short-Term Memory based Deep Recurrent Neural Networks for Large Vocabulary Speech Recognition|last2=Wu|first2=Xihong|class=cs.CL|year=2014}}</ref><ref name="zen2015">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=Unidirectional Long Short-Term Memory Recurrent Neural Network with Recurrent Output Layer for Low-Latency Speech Synthesis|last=Zen|first=Heiga|last2=Sak|first2=Hasim|date=2015|website=Google.com|publisher=ICASSP|pages=4470–4474|accessdate=}}</ref><ref name="CNNspeech2013">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=A deep convolutional neural network using heterogeneous pooling for trading acoustic invariance with phonetic confusion|last=Deng|first=L.|last2=Abdel-Hamid|first2=O.|date=2013|website=Google.com|publisher=ICASSP|accessdate=|last3=Yu|first3=D.}}</ref><ref name=":2">{{Cite book |doi=10.1109/icassp.2013.6639347|isbn=978-1-4799-0356-6|chapter=Deep convolutional neural networks for LVCSR|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8614–8618|year=2013|last1=Sainath|first1=Tara N.|last2=Mohamed|first2=Abdel-Rahman|last3=Kingsbury|first3=Brian|last4=Ramabhadran|first4=Bhuvana}}</ref> but are more successful in computer vision.

The impact of deep learning in industry began in the early 2000s, when CNNs already processed an estimated 10% to 20% of all the checks written in the US, according to Yann LeCun.<ref name="lecun2016slides">[[Yann LeCun]] (2016). Slides on Deep Learning [https://indico.cern.ch/event/510372/ Online]</ref> Industrial applications of deep learning to large-scale speech recognition started around 2010.

The 2009 NIPS Workshop on Deep Learning for Speech Recognition<ref name="NIPS2009" /> was motivated by the limitations of deep generative models of speech, and the possibility that given more capable hardware and large-scale data sets that deep neural nets (DNN) might become practical. It was believed that pre-training DNNs using generative models of deep belief nets (DBN) would overcome the main difficulties of neural nets.<ref name="HintonKeynoteICASSP2013" /> However, it was discovered that replacing pre-training with large amounts of training data for straightforward backpropagation when using DNNs with large, context-dependent output layers produced error rates dramatically lower than then-state-of-the-art Gaussian mixture model (GMM)/Hidden Markov Model (HMM) and also than more-advanced generative model-based systems.<ref name="HintonDengYu2012">{{cite journal | last1 = Hinton | first1 = G. | last2 = Deng | first2 = L. | last3 = Yu | first3 = D. | last4 = Dahl | first4 = G. | last5 = Mohamed | first5 = A. | last6 = Jaitly | first6 = N. | last7 = Senior | first7 = A. | last8 = Vanhoucke | first8 = V. | last9 = Nguyen | first9 = P. | last10 = Sainath | first10 = T. | last11 = Kingsbury | first11 = B. | year = 2012 | title = Deep Neural Networks for Acoustic Modeling in Speech Recognition: The Shared Views of Four Research Groups| url= | journal = IEEE Signal Processing Magazine | volume = 29 | issue = 6| pages = 82–97 | doi=10.1109/msp.2012.2205597}}</ref><ref name="patent2011">D. Yu, L. Deng, G. Li, and F. Seide (2011). "Discriminative pretraining of deep neural networks," U.S. Patent Filing.</ref> The nature of the recognition errors produced by the two types of systems was characteristically different,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009">NIPS Workshop: Deep Learning for Speech Recognition and Related Applications, Whistler, BC, Canada, Dec. 2009 (Organizers: Li Deng, Geoff Hinton, D. Yu).</ref> offering technical insights into how to integrate deep learning into the existing highly efficient, run-time speech decoding system deployed by all major speech recognition systems.<ref name="BOOK2014" /><ref name="ReferenceA">{{cite book|last2=Deng|first2=L.|date=2014|title=Automatic Speech Recognition: A Deep Learning Approach (Publisher: Springer)|url={{google books |plainurl=y |id=rUBTBQAAQBAJ}}|pages=|isbn=978-1-4471-5779-3|via=|last1=Yu|first1=D.}}</ref><ref>{{cite web|title=Deng receives prestigious IEEE Technical Achievement Award - Microsoft Research|url=https://www.microsoft.com/en-us/research/blog/deng-receives-prestigious-ieee-technical-achievement-award/|website=Microsoft Research|date=3 December 2015}}</ref> Analysis around 2009-2010, contrasted the GMM (and other generative speech models) vs. DNN models, stimulated early industrial investment in deep learning for speech recognition,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009" /> eventually leading to pervasive and dominant use in that industry. That analysis was done with comparable performance (less than 1.5% in error rate) between discriminative DNNs and generative models.<ref name="HintonDengYu2012" /><ref name="ReferenceICASSP2013">{{cite journal|last2=Hinton|first2=G.|last3=Kingsbury|first3=B.|date=2013|title=New types of deep neural network learning for speech recognition and related applications: An overview (ICASSP)|url=https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/ICASSP-2013-DengHintonKingsbury-revised.pdf|journal=|pages=|via=|last1=Deng|first1=L.}}</ref><ref name="HintonKeynoteICASSP2013">Keynote talk: Recent Developments in Deep Neural Networks. ICASSP, 2013 (by Geoff Hinton).</ref><ref name="interspeech2014Keynote">{{Cite web|url=https://www.superlectures.com/interspeech2014/downloadFile?id=6&type=slides&filename=achievements-and-challenges-of-deep-learning-from-speech-analysis-and-recognition-to-language-and-multimodal-processing|title=Keynote talk: 'Achievements and Challenges of Deep Learning - From Speech Analysis and Recognition To Language and Multimodal Processing'|last=Li|first=Deng|date=September 2014|website=Interspeech|accessdate=}}</ref>

In 2010, researchers extended deep learning from TIMIT to large vocabulary speech recognition, by adopting large output layers of the DNN based on context-dependent HMM states constructed by [[decision tree]]s.<ref name="Roles2010">{{cite journal|last1=Yu|first1=D.|last2=Deng|first2=L.|date=2010|title=Roles of Pre-Training and Fine-Tuning in Context-Dependent DBN-HMMs for Real-World Speech Recognition|url=https://www.microsoft.com/en-us/research/publication/roles-of-pre-training-and-fine-tuning-in-context-dependent-dbn-hmms-for-real-world-speech-recognition/|journal=NIPS Workshop on Deep Learning and Unsupervised Feature Learning|pages=|via=}}</ref><ref>{{Cite journal|last=Seide|first=F.|last2=Li|first2=G.|last3=Yu|first3=D.|date=2011|title=Conversational speech transcription using context-dependent deep neural networks|url=https://www.microsoft.com/en-us/research/publication/conversational-speech-transcription-using-context-dependent-deep-neural-networks|journal=Interspeech|pages=|via=}}</ref><ref>{{Cite journal|last=Deng|first=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Mike|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|date=2013-05-01|title=Recent Advances in Deep Learning for Speech Research at Microsoft|url=https://www.microsoft.com/en-us/research/publication/recent-advances-in-deep-learning-for-speech-research-at-microsoft/|journal=Microsoft Research}}</ref><ref name="ReferenceA" />

Advances in hardware have enabled renewed interest in deep learning. In 2009, [[Nvidia]] was involved in what was called the “big bang” of deep learning, “as deep-learning neural networks were trained with Nvidia [[graphics processing unit]]s (GPUs).”<ref>{{cite web|url=https://venturebeat.com/2016/04/05/nvidia-ceo-bets-big-on-deep-learning-and-vr/|title=Nvidia CEO bets big on deep learning and VR|date=April 5, 2016|publisher=[[Venture Beat]]}}</ref> That year, [[Google Brain]] used Nvidia GPUs to create capable DNNs. While there, [[Andrew Ng]] determined that GPUs could increase the speed of deep-learning systems by about 100 times.<ref>{{cite news|url=https://www.economist.com/news/special-report/21700756-artificial-intelligence-boom-based-old-idea-modern-twist-not|title=From not working to neural networking|newspaper=[[The Economist]]}}</ref> In particular, GPUs are well-suited for the matrix/vector computations involved in machine learning.<ref name="jung2004">{{cite journal | last1 = Oh | first1 = K.-S. | last2 = Jung | first2 = K. | year = 2004 | title = GPU implementation of neural networks | url= | journal = Pattern Recognition | volume = 37 | issue = 6| pages = 1311–1314 | doi=10.1016/j.patcog.2004.01.013}}</ref><ref>"[https://www.academia.edu/40135801 A Survey of Techniques for Optimizing Deep Learning on GPUs]", S. Mittal and S. Vaishay, Journal of Systems Architecture, 2019</ref><ref name="chellapilla2006">Chellapilla, K., Puri, S., and Simard, P. (2006). High performance convolutional neural networks for document processing. International Workshop on Frontiers in Handwriting Recognition.</ref> GPUs speed up training algorithms by orders of magnitude, reducing running times from weeks to days.<ref name=":3">{{Cite journal|last=Cireşan|first=Dan Claudiu|last2=Meier|first2=Ueli|last3=Gambardella|first3=Luca Maria|last4=Schmidhuber|first4=Jürgen|date=2010-09-21|title=Deep, Big, Simple Neural Nets for Handwritten Digit Recognition|journal=Neural Computation|volume=22|issue=12|pages=3207–3220|doi=10.1162/neco_a_00052|pmid=20858131|issn=0899-7667|arxiv=1003.0358}}</ref><ref>{{Cite journal|last=Raina|first=Rajat|last2=Madhavan|first2=Anand|last3=Ng|first3=Andrew Y.|date=2009|title=Large-scale Deep Unsupervised Learning Using Graphics Processors|journal=Proceedings of the 26th Annual International Conference on Machine Learning|series=ICML '09|location=New York, NY, USA|publisher=ACM|pages=873–880|doi=10.1145/1553374.1553486|isbn=9781605585161|citeseerx=10.1.1.154.372|url=https://www.semanticscholar.org/paper/e337c5e4c23999c36f64bcb33ebe6b284e1bcbf1}}</ref> Further, specialized hardware and algorithm optimizations can be used for efficient processing of deep learning models.<ref name="sze2017">{{cite arXiv
|title= Efficient Processing of Deep Neural Networks: A Tutorial and Survey
|last1=Sze |first1=Vivienne
|last2=Chen |first2=Yu-Hsin
|last3=Yang |first3=Tien-Ju
|last4=Emer |first4=Joel
|eprint=1703.09039
|year=2017
|class=cs.CV }}</ref>

=== Deep learning revolution ===
[[File:AI-ML-DL.png|thumb|How deep learning is a subset of machine learning and how machine learning is a subset of artificial intelligence (AI).]]
In 2012, a team led by George E. Dahl won the "Merck Molecular Activity Challenge" using multi-task deep neural networks to predict the [[biomolecular target]] of one drug.<ref name="MERCK2012">{{cite web|url=https://www.kaggle.com/c/MerckActivity/details/winners|title=Announcement of the winners of the Merck Molecular Activity Challenge}}</ref><ref name=":5">{{Cite web|url=http://www.datascienceassn.org/content/multi-task-neural-networks-qsar-predictions|title=Multi-task Neural Networks for QSAR Predictions {{!}} Data Science Association|website=www.datascienceassn.org|accessdate=2017-06-14}}</ref> In 2014, Hochreiter's group used deep learning to detect off-target and toxic effects of environmental chemicals in nutrients, household products and drugs and won the "Tox21 Data Challenge" of [[NIH]], [[FDA]] and [[National Center for Advancing Translational Sciences|NCATS]].<ref name="TOX21">"Toxicology in the 21st century Data Challenge"</ref><ref name="TOX21Data">{{cite web|url=https://tripod.nih.gov/tox21/challenge/leaderboard.jsp|title=NCATS Announces Tox21 Data Challenge Winners}}</ref><ref name=":11">{{cite web|url=http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|title=Archived copy|archiveurl=https://web.archive.org/web/20150228225709/http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|archivedate=2015-02-28|url-status=dead|accessdate=2015-03-05}}</ref>

Significant additional impacts in image or object recognition were felt from 2011 to 2012. Although CNNs trained by backpropagation had been around for decades, and GPU implementations of NNs for years, including CNNs, fast implementations of CNNs with max-pooling on GPUs in the style of Ciresan and colleagues were needed to progress on computer vision.<ref name="jung2004" /><ref name="chellapilla2006" /><ref name="LECUN1989" /><ref name=":6">{{Cite journal|last=Ciresan|first=D. C.|last2=Meier|first2=U.|last3=Masci|first3=J.|last4=Gambardella|first4=L. M.|last5=Schmidhuber|first5=J.|date=2011|title=Flexible, High Performance Convolutional Neural Networks for Image Classification|url=http://ijcai.org/papers11/Papers/IJCAI11-210.pdf|journal=International Joint Conference on Artificial Intelligence|pages=|doi=10.5591/978-1-57735-516-8/ijcai11-210|via=}}</ref><ref name="SCHIDHUB" /> In 2011, this approach achieved for the first time superhuman performance in a visual pattern recognition contest. Also in 2011, it won the ICDAR Chinese handwriting contest, and in May 2012, it won the ISBI image segmentation contest.<ref name=":8">{{Cite book|url=http://papers.nips.cc/paper/4741-deep-neural-networks-segment-neuronal-membranes-in-electron-microscopy-images.pdf|title=Advances in Neural Information Processing Systems 25|last=Ciresan|first=Dan|last2=Giusti|first2=Alessandro|last3=Gambardella|first3=Luca M.|last4=Schmidhuber|first4=Juergen|date=2012|publisher=Curran Associates, Inc.|editor-last=Pereira|editor-first=F.|pages=2843–2851|editor-last2=Burges|editor-first2=C. J. C.|editor-last3=Bottou|editor-first3=L.|editor-last4=Weinberger|editor-first4=K. Q.}}</ref> Until 2011, CNNs did not play a major role at computer vision conferences, but in June 2012, a paper by Ciresan et al. at the leading conference CVPR<ref name=":9" /> showed how max-pooling CNNs on GPU can dramatically improve many vision benchmark records. In October 2012, a similar system by Krizhevsky et al.<ref name="krizhevsky2012" /> won the large-scale [[ImageNet competition]] by a significant margin over shallow machine learning methods. In November 2012, Ciresan et al.'s system also won the ICPR contest on analysis of large medical images for cancer detection, and in the following year also the MICCAI Grand Challenge on the same topic.<ref name="ciresan2013miccai">{{Cite journal|last=Ciresan|first=D.|last2=Giusti|first2=A.|last3=Gambardella|first3=L.M.|last4=Schmidhuber|first4=J.|date=2013|title=Mitosis Detection in Breast Cancer Histology Images using Deep Neural Networks|journal=Proceedings MICCAI|volume=7908|issue=Pt 2|pages=411–418|doi=10.1007/978-3-642-40763-5_51|pmid=24579167|series=Lecture Notes in Computer Science|isbn=978-3-642-38708-1}}</ref> In 2013 and 2014, the error rate on the ImageNet task using deep learning was further reduced, following a similar trend in large-scale speech recognition. The [[Stephen Wolfram|Wolfram]] Image Identification project publicized these improvements.<ref>{{Cite web|url=https://www.imageidentify.com/|title=The Wolfram Language Image Identification Project|website=www.imageidentify.com|accessdate=2017-03-22}}</ref>

Image classification was then extended to the more challenging task of [[Automatic image annotation|generating descriptions]] (captions) for images, often as a combination of CNNs and LSTMs.<ref name="1411.4555">{{cite arxiv |eprint=1411.4555|last1=Vinyals|first1=Oriol|title=Show and Tell: A Neural Image Caption Generator|last2=Toshev|first2=Alexander|last3=Bengio|first3=Samy|last4=Erhan|first4=Dumitru|class=cs.CV|year=2014}}.</ref><ref name="1411.4952">{{cite arxiv |eprint=1411.4952|last1=Fang|first1=Hao|title=From Captions to Visual Concepts and Back|last2=Gupta|first2=Saurabh|last3=Iandola|first3=Forrest|last4=Srivastava|first4=Rupesh|last5=Deng|first5=Li|last6=Dollár|first6=Piotr|last7=Gao|first7=Jianfeng|last8=He|first8=Xiaodong|last9=Mitchell|first9=Margaret|last10=Platt|first10=John C|last11=Lawrence Zitnick|first11=C|last12=Zweig|first12=Geoffrey|class=cs.CV|year=2014}}.</ref><ref name="1411.2539">{{cite arxiv |eprint=1411.2539|last1=Kiros|first1=Ryan|title=Unifying Visual-Semantic Embeddings with Multimodal Neural Language Models|last2=Salakhutdinov|first2=Ruslan|last3=Zemel|first3=Richard S|class=cs.LG|year=2014}}.</ref><ref>{{Cite journal|last=Zhong|first=Sheng-hua|last2=Liu|first2=Yan|last3=Liu|first3=Yang|date=2011|title=Bilinear Deep Learning for Image Classification|journal=Proceedings of the 19th ACM International Conference on Multimedia|series=MM '11|location=New York, NY, USA|publisher=ACM|pages=343–352|doi=10.1145/2072298.2072344|isbn=9781450306164|url=https://www.semanticscholar.org/paper/e1bbfb2c7ef74445b4fad9199b727464129df582}}</ref>

Some researchers assess that the October 2012 ImageNet victory anchored the start of a "deep learning revolution" that has transformed the AI industry.<ref>{{cite news|title=Why Deep Learning Is Suddenly Changing Your Life|url=http://fortune.com/ai-artificial-intelligence-deep-machine-learning/|accessdate=13 April 2018|work=Fortune|date=2016}}</ref>

In March 2019, [[Yoshua Bengio]], [[Geoffrey Hinton]] and [[Yann LeCun]] were awarded the [[Turing Award]] for conceptual and engineering breakthroughs that have made deep neural networks a critical component of computing.

== Neural networks ==

=== Artificial neural networks ===
{{Main|Artificial neural network}}
'''Artificial neural networks''' ('''ANNs''') or '''[[Connectionism|connectionist]] systems''' are computing systems inspired by the [[biological neural network]]s that constitute animal brains. Such systems learn (progressively improve their ability) to do tasks by considering examples, generally without task-specific programming. For example, in image recognition, they might learn to identify images that contain cats by analyzing example images that have been manually [[Labeled data|labeled]] as "cat" or "no cat" and using the analytic results to identify cats in other images. They have found most use in applications difficult to express with a traditional computer algorithm using [[rule-based programming]].

An ANN is based on a collection of connected units called [[artificial neuron]]s, (analogous to biological neurons in a [[Brain|biological brain]]). Each connection ([[synapse]]) between neurons can transmit a signal to another neuron. The receiving (postsynaptic) neuron can process the signal(s) and then signal downstream neurons connected to it. Neurons may have state, generally represented by [[real numbers]], typically between 0 and 1. Neurons and synapses may also have a weight that varies as learning proceeds, which can increase or decrease the strength of the signal that it sends downstream.

Typically, neurons are organized in layers. Different layers may perform different kinds of transformations on their inputs. Signals travel from the first (input), to the last (output) layer, possibly after traversing the layers multiple times.

The original goal of the neural network approach was to solve problems in the same way that a human brain would. Over time, attention focused on matching specific mental abilities, leading to deviations from biology such as backpropagation, or passing information in the reverse direction and adjusting the network to reflect that information.

Neural networks have been used on a variety of tasks, including computer vision, [[speech recognition]], [[machine translation]], [[social network]] filtering, [[general game playing|playing board and video games]] and medical diagnosis.

As of 2017, neural networks typically have a few thousand to a few million units and millions of connections. Despite this number being several order of magnitude less than the number of neurons on a human brain, these networks can perform many tasks at a level beyond that of humans (e.g., recognizing faces, playing "Go"<ref>{{Cite journal|last=Silver|first=David|last2=Huang|first2=Aja|last3=Maddison|first3=Chris J.|last4=Guez|first4=Arthur|last5=Sifre|first5=Laurent|last6=Driessche|first6=George van den|last7=Schrittwieser|first7=Julian|last8=Antonoglou|first8=Ioannis|last9=Panneershelvam|first9=Veda|date=January 2016|title=Mastering the game of Go with deep neural networks and tree search|journal=Nature|volume=529|issue=7587|pages=484–489|doi=10.1038/nature16961|issn=1476-4687|pmid=26819042|bibcode=2016Natur.529..484S|url=https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}</ref> ).

=== Deep neural networks ===
{{technical|section|date=July 2016}}
A deep neural network (DNN) is an [[artificial neural network]] (ANN) with multiple layers between the input and output layers.<ref name="BENGIODEEP" /><ref name="SCHIDHUB" /> The DNN finds the correct mathematical manipulation to turn the input into the output, whether it be a [[linear relationship]] or a non-linear relationship. The network moves through the layers calculating the probability of each output. For example, a DNN that is trained to recognize dog breeds will go over the given image and calculate the probability that the dog in the image is a certain breed. The user can review the results and select which probabilities the network should display (above a certain threshold, etc.) and return the proposed label. Each mathematical manipulation as such is considered a layer, and complex DNN have many layers, hence the name "deep" networks.

DNNs can model complex non-linear relationships. DNN architectures generate compositional models where the object is expressed as a layered composition of [[Primitive data type|primitives]].<ref>{{Cite journal|last=Szegedy|first=Christian|last2=Toshev|first2=Alexander|last3=Erhan|first3=Dumitru|date=2013|title=Deep neural networks for object detection|url=https://papers.nips.cc/paper/5207-deep-neural-networks-for-object-detection|journal=Advances in Neural Information Processing Systems|pages=2553–2561|via=}}</ref> The extra layers enable composition of features from lower layers, potentially modeling complex data with fewer units than a similarly performing shallow network.<ref name="BENGIODEEP" />

Deep architectures include many variants of a few basic approaches. Each architecture has found success in specific domains. It is not always possible to compare the performance of multiple architectures, unless they have been evaluated on the same data sets.

DNNs are typically feedforward networks in which data flows from the input layer to the output layer without looping back. At first, the DNN creates a map of virtual neurons and assigns random numerical values, or "weights", to connections between them. The weights and inputs are multiplied and return an output between 0 and 1. If the network did not accurately recognize a particular pattern, an algorithm would adjust the weights.<ref>{{Cite news|url=https://www.technologyreview.com/s/513696/deep-learning/|title=Is Artificial Intelligence Finally Coming into Its Own?|last=Hof|first=Robert D.|work=MIT Technology Review|access-date=2018-07-10}}</ref> That way the algorithm can make certain parameters more influential, until it determines the correct mathematical manipulation to fully process the data.

[[Recurrent neural networks]] (RNNs), in which data can flow in any direction, are used for applications such as [[language model]]ing.<ref name="gers2001">{{cite journal|last1=Gers|first1=Felix A.|last2=Schmidhuber|first2=Jürgen|year=2001|title=LSTM Recurrent Networks Learn Simple Context Free and Context Sensitive Languages|url=http://elartu.tntu.edu.ua/handle/lib/30719|journal= IEEE Transactions on Neural Networks|volume=12|issue=6|pages=1333–1340|doi=10.1109/72.963769|pmid=18249962}}</ref><ref name="NIPS2014"/><ref name="vinyals2016">{{cite arxiv |eprint=1602.02410|last1=Jozefowicz|first1=Rafal|title=Exploring the Limits of Language Modeling|last2=Vinyals|first2=Oriol|last3=Schuster|first3=Mike|last4=Shazeer|first4=Noam|last5=Wu|first5=Yonghui|class=cs.CL|year=2016}}</ref><ref name="gillick2015">{{cite arxiv |eprint=1512.00103|last1=Gillick|first1=Dan|title=Multilingual Language Processing from Bytes|last2=Brunk|first2=Cliff|last3=Vinyals|first3=Oriol|last4=Subramanya|first4=Amarnag|class=cs.CL|year=2015}}</ref><ref name="MIKO2010">{{Cite journal|last=Mikolov|first=T.|display-authors=etal|date=2010|title=Recurrent neural network based language model|url=http://www.fit.vutbr.cz/research/groups/speech/servite/2010/rnnlm_mikolov.pdf|journal=Interspeech|pages=|via=}}</ref> Long short-term memory is particularly effective for this use.<ref name=":0" /><ref name=":10">{{Cite web|url=https://www.researchgate.net/publication/220320057|title=Learning Precise Timing with LSTM Recurrent Networks (PDF Download Available)|website=ResearchGate|accessdate=2017-06-13}}</ref>

[[Convolutional neural network|Convolutional deep neural networks (CNNs)]] are used in computer vision.<ref name="LECUN86">{{cite journal |last1=LeCun |first1=Y. |display-authors=etal |year= 1998|title=Gradient-based learning applied to document recognition |url= |journal=Proceedings of the IEEE |volume=86 |issue=11 |pages=2278–2324 |doi=10.1109/5.726791}}</ref> CNNs also have been applied to [[acoustic model]]ing for automatic speech recognition (ASR).<ref name=":2" />

==== Challenges ====
As with ANNs, many issues can arise with naively trained DNNs. Two common issues are [[overfitting]] and computation time.

DNNs are prone to overfitting because of the added layers of abstraction, which allow them to model rare dependencies in the training data. [[Regularization (mathematics)|Regularization]] methods such as Ivakhnenko's unit pruning<ref name="ivak1971"/> or [[weight decay]] (<math> \ell_2 </math>-regularization) or [[sparse matrix|sparsity]] (<math> \ell_1 </math>-regularization) can be applied during training to combat overfitting.<ref>{{Cite book |doi=10.1109/icassp.2013.6639349|isbn=978-1-4799-0356-6|arxiv=1212.0901|citeseerx=10.1.1.752.9151|chapter=Advances in optimizing recurrent networks|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8624–8628|year=2013|last1=Bengio|first1=Yoshua|last2=Boulanger-Lewandowski|first2=Nicolas|last3=Pascanu|first3=Razvan}}</ref> Alternatively dropout regularization randomly omits units from the hidden layers during training. This helps to exclude rare dependencies.<ref name="DAHL2013">{{Cite journal|last=Dahl|first=G.|display-authors=etal|date=2013|title=Improving DNNs for LVCSR using rectified linear units and dropout|url=http://www.cs.toronto.edu/~gdahl/papers/reluDropoutBN_icassp2013.pdf|journal=ICASSP|pages=|via=}}</ref> Finally, data can be augmented via methods such as cropping and rotating such that smaller training sets can be increased in size to reduce the chances of overfitting.<ref>{{Cite web|url=https://www.coursera.org/learn/convolutional-neural-networks/lecture/AYzbX/data-augmentation|title=Data Augmentation - deeplearning.ai {{!}} Coursera|website=Coursera|accessdate=2017-11-30}}</ref>

DNNs must consider many training parameters, such as the size (number of layers and number of units per layer), the [[learning rate]], and initial weights. [[Hyperparameter optimization#Grid search|Sweeping through the parameter space]] for optimal parameters may not be feasible due to the cost in time and computational resources. Various tricks, such as batching (computing the gradient on several training examples at once rather than individual examples)<ref name="RBMTRAIN">{{Cite journal|last=Hinton|first=G. E.|date=2010|title=A Practical Guide to Training Restricted Boltzmann Machines|url=https://www.researchgate.net/publication/221166159|journal=Tech. Rep. UTML TR 2010-003|pages=|via=}}</ref> speed up computation. Large processing capabilities of many-core architectures (such as GPUs or the Intel Xeon Phi) have produced significant speedups in training, because of the suitability of such processing architectures for the matrix and vector computations.<ref>{{cite book|last1=You|first1=Yang|title=Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis on - SC '17|pages=1–12|last2=Buluç|first2=Aydın|last3=Demmel|first3=James|chapter=Scaling deep learning on GPU and knights landing clusters|chapter-url=https://dl.acm.org/citation.cfm?doid=3126908.3126912|publisher=SC '17, ACM|date=November 2017|accessdate=5 March 2018|doi=10.1145/3126908.3126912|isbn=9781450351140|url=http://www.escholarship.org/uc/item/6ch40821}}</ref><ref>{{cite journal|last1=Viebke|first1=André|last2=Memeti|first2=Suejb|last3=Pllana|first3=Sabri|last4=Abraham|first4=Ajith|title=CHAOS: a parallelization scheme for training convolutional neural networks on Intel Xeon Phi|journal=The Journal of Supercomputing|volume=75|pages=197–227|doi=10.1007/s11227-017-1994-x|accessdate=|arxiv=1702.07908|bibcode=2017arXiv170207908V|url=https://www.semanticscholar.org/paper/aa8a4d2de94cc0a8ccff21f651c005613e8ec0e8|year=2019}}</ref>

Alternatively, engineers may look for other types of neural networks with more straightforward and convergent training algorithms. CMAC ([[cerebellar model articulation controller]]) is one such kind of neural network. It doesn't require learning rates or randomized initial weights for CMAC. The training process can be guaranteed to converge in one step with a new batch of data, and the computational complexity of the training algorithm is linear with respect to the number of neurons involved.<ref name=Qin1>Ting Qin, et al. "A learning algorithm of CMAC based on RLS." Neural Processing Letters 19.1 (2004): 49-61.</ref><ref name=Qin2>Ting Qin, et al. "[http://www-control.eng.cam.ac.uk/Homepage/papers/cued_control_997.pdf Continuous CMAC-QRLS and its systolic array]." Neural Processing Letters 22.1 (2005): 1-16.</ref>

== Applications ==

=== Automatic speech recognition ===
{{Main|Speech recognition}}

Large-scale automatic speech recognition is the first and most convincing successful case of deep learning. LSTM RNNs can learn "Very Deep Learning" tasks<ref name="SCHIDHUB"/> that involve multi-second intervals containing speech events separated by thousands of discrete time steps, where one time step corresponds to about 10 ms. LSTM with forget gates<ref name=":10" /> is competitive with traditional speech recognizers on certain tasks.<ref name="graves2003"/>

The initial success in speech recognition was based on small-scale recognition tasks based on TIMIT. The data set contains 630 speakers from eight major [[dialect]]s of [[American English]], where each speaker reads 10 sentences.<ref name="LDCTIMIT">''TIMIT Acoustic-Phonetic Continuous Speech Corpus'' Linguistic Data Consortium, Philadelphia.</ref> Its small size lets many configurations be tried. More importantly, the TIMIT task concerns phone-sequence recognition, which, unlike word-sequence recognition, allows weak phone [[bigram]] language models. This lets the strength of the acoustic modeling aspects of speech recognition be more easily analyzed. The error rates listed below, including these early results and measured as percent phone error rates (PER), have been summarized since 1991.

{| class="wikitable"
|-
! Method !! Percent phone<br>error rate (PER) (%)
|-
| Randomly Initialized RNN<ref>{{cite journal |last1=Robinson |first1=Tony |authorlink=Tony Robinson (speech recognition)|title=Several Improvements to a Recurrent Error Propagation Network Phone Recognition System |journal=Cambridge University Engineering Department Technical Report |date=30 September 1991 |volume=CUED/F-INFENG/TR82 |doi=10.13140/RG.2.2.15418.90567 }}</ref>|| 26.1
|-
| Bayesian Triphone GMM-HMM || 25.6
|-
| Hidden Trajectory (Generative) Model|| 24.8
|-
| Monophone Randomly Initialized DNN|| 23.4
|-
| Monophone DBN-DNN|| 22.4
|-
| Triphone GMM-HMM with BMMI Training|| 21.7
|-
| Monophone DBN-DNN on fbank || 20.7
|-
| Convolutional DNN<ref name="CNN-2014">{{cite journal|last1=Abdel-Hamid|first1=O.|title=Convolutional Neural Networks for Speech Recognition|journal=IEEE/ACM Transactions on Audio, Speech, and Language Processing|date=2014|volume=22|issue=10|pages=1533–1545|doi=10.1109/taslp.2014.2339736|display-authors=etal|url=https://zenodo.org/record/891433}}</ref>|| 20.0
|-
| Convolutional DNN w. Heterogeneous Pooling|| 18.7
|-
| Ensemble DNN/CNN/RNN<ref name="EnsembleDL">{{cite journal|last2=Platt|first2=J.|date=2014|title=Ensemble Deep Learning for Speech Recognition|url=https://pdfs.semanticscholar.org/8201/55ecb57325503183253b8796de5f4535eb16.pdf|journal=Proc. Interspeech|pages=|via=|last1=Deng|first1=L.}}</ref>|| 18.3
|-
| Bidirectional LSTM|| 17.9
|-
| Hierarchical Convolutional Deep Maxout Network<ref name="HCDMM">{{cite journal|last1=Tóth|first1=Laszló|date=2015|title=Phone Recognition with Hierarchical Convolutional Deep Maxout Networks|journal=EURASIP Journal on Audio, Speech, and Music Processing|volume=2015|doi=10.1186/s13636-015-0068-3|url=http://publicatio.bibl.u-szeged.hu/5976/1/EURASIP2015.pdf}}</ref> || 16.5
|}

The debut of DNNs for speaker recognition in the late 1990s and speech recognition around 2009-2011 and of LSTM around 2003-2007, accelerated progress in eight major areas:<ref name="BOOK2014" /><ref name="interspeech2014Keynote" /><ref name="ReferenceA" />

* Scale-up/out and accelerated DNN training and decoding
* Sequence discriminative training
* Feature processing by deep models with solid understanding of the underlying mechanisms
* Adaptation of DNNs and related deep models
* [[Multi-task learning|Multi-task]] and [[Inductive transfer|transfer learning]] by DNNs and related deep models
* CNNs and how to design them to best exploit [[domain knowledge]] of speech
* RNN and its rich LSTM variants
* Other types of deep models including tensor-based models and integrated deep generative/discriminative models.

All major commercial speech recognition systems (e.g., Microsoft [[Cortana (software)|Cortana]], [[Xbox]], [[Skype Translator]], [[Amazon Alexa]], [[Google Now]], [[Siri|Apple Siri]], [[Baidu]] and [[IFlytek|iFlyTek]] voice search, and a range of [[Nuance Communications|Nuance]] speech products, etc.) are based on deep learning.<ref name=BOOK2014 /><ref>{{Cite journal|url=https://www.wired.com/2014/12/skype-used-ai-build-amazing-new-language-translator/|title=How Skype Used AI to Build Its Amazing New Language Translator {{!}} WIRED|journal=Wired|accessdate=2017-06-14|date=2014-12-17|last1=McMillan|first1=Robert}}</ref><ref name="Baidu">{{cite arxiv |eprint=1412.5567|last1=Hannun|first1=Awni|title=Deep Speech: Scaling up end-to-end speech recognition|last2=Case|first2=Carl|last3=Casper|first3=Jared|last4=Catanzaro|first4=Bryan|last5=Diamos|first5=Greg|last6=Elsen|first6=Erich|last7=Prenger|first7=Ryan|last8=Satheesh|first8=Sanjeev|last9=Sengupta|first9=Shubho|last10=Coates|first10=Adam|last11=Ng|first11=Andrew Y|class=cs.CL|year=2014}}</ref><ref>{{Cite web|url=http://research.microsoft.com/en-US/people/deng/ieee-icassp-plenary-2016-mar24-lideng-posted.pdf|title=Plenary presentation at ICASSP-2016|date=|website=|accessdate=}}</ref>

=== Image recognition ===
{{Main|Computer vision}}

A common evaluation set for image classification is the MNIST database data set. MNIST is composed of handwritten digits and includes 60,000 training examples and 10,000 test examples. As with TIMIT, its small size lets users test multiple configurations. A comprehensive list of results on this set is available.<ref name="YANNMNIST">{{cite web|url=http://yann.lecun.com/exdb/mnist/.|title=MNIST handwritten digit database, Yann LeCun, Corinna Cortes and Chris Burges|website=yann.lecun.com}}</ref>

Deep learning-based image recognition has become "superhuman", producing more accurate results than human contestants. This first occurred in 2011.<ref name=":7">{{Cite journal|last=Cireşan|first=Dan|last2=Meier|first2=Ueli|last3=Masci|first3=Jonathan|last4=Schmidhuber|first4=Jürgen|date=August 2012|title=Multi-column deep neural network for traffic sign classification|journal=Neural Networks|series=Selected Papers from IJCNN 2011|volume=32|pages=333–338|doi=10.1016/j.neunet.2012.02.023|pmid=22386783|citeseerx=10.1.1.226.8219}}</ref>

Deep learning-trained vehicles now interpret 360° camera views.<ref>[http://www.technologyreview.com/news/533936/nvidia-demos-a-car-computer-trained-with-deep-learning/ Nvidia Demos a Car Computer Trained with "Deep Learning"] (2015-01-06), David Talbot, ''[[MIT Technology Review]]''</ref> Another example is Facial Dysmorphology Novel Analysis (FDNA) used to analyze cases of human malformation connected to a large database of genetic syndromes.

=== Visual art processing ===
Closely related to the progress that has been made in image recognition is the increasing application of deep learning techniques to various visual art tasks. DNNs have proven themselves capable, for example, of a) identifying the style period of a given painting, b) [[Neural Style Transfer]] - capturing the style of a given artwork and applying it in a visually pleasing manner to an arbitrary photograph or video, and c) generating striking imagery based on random visual input fields.<ref>{{cite journal |author1=G. W. Smith|author2=Frederic Fol Leymarie|date=10 April 2017|title=The Machine as Artist: An Introduction|journal=Arts|volume=6|issue=4|pages=5|doi=10.3390/arts6020005}}</ref><ref>{{cite journal |author=Blaise Agüera y Arcas|date=29 September 2017|title=Art in the Age of Machine Intelligence|journal=Arts|volume=6|issue=4|pages=18|doi=10.3390/arts6040018}}</ref>

=== Natural language processing ===
{{Main|Natural language processing}}
Neural networks have been used for implementing language models since the early 2000s.<ref name="gers2001" /><ref>{{Cite journal|last=Bengio|first=Yoshua|last2=Ducharme|first2=Réjean|last3=Vincent|first3=Pascal|last4=Janvin|first4=Christian|date=March 2003|title=A Neural Probabilistic Language Model|url=http://dl.acm.org/citation.cfm?id=944919.944966|journal=J. Mach. Learn. Res.|volume=3|pages=1137–1155|issn=1532-4435}}</ref> LSTM helped to improve machine translation and language modeling.<ref name="NIPS2014" /><ref name="vinyals2016" /><ref name="gillick2015" />

Other key techniques in this field are negative sampling<ref name="GoldbergLevy2014">{{cite arXiv|last1=Goldberg|first1=Yoav|last2=Levy|first2=Omar|title=word2vec Explained: Deriving Mikolov et al.'s Negative-Sampling Word-Embedding Method|eprint=1402.3722|class=cs.CL|year=2014}}</ref> and [[word embedding]]. Word embedding, such as ''[[word2vec]]'', can be thought of as a representational layer in a deep learning architecture that transforms an atomic word into a positional representation of the word relative to other words in the dataset; the position is represented as a point in a [[vector space]]. Using word embedding as an RNN input layer allows the network to parse sentences and phrases using an effective compositional vector grammar. A compositional vector grammar can be thought of as [[probabilistic context free grammar]] (PCFG) implemented by an RNN.<ref name="SocherManning2014">{{cite web|last1=Socher|first1=Richard|last2=Manning|first2=Christopher|title=Deep Learning for NLP|url=http://nlp.stanford.edu/courses/NAACL2013/NAACL2013-Socher-Manning-DeepLearning.pdf|accessdate=26 October 2014}}</ref> Recursive auto-encoders built atop word embeddings can assess sentence similarity and detect paraphrasing.<ref name="SocherManning2014" /> Deep neural architectures provide the best results for [[Statistical parsing|constituency parsing]],<ref>{{Cite journal |url= http://aclweb.org/anthology/P/P13/P13-1045.pdf|title = Parsing With Compositional Vector Grammars|last = Socher|first = Richard|date = 2013|journal = Proceedings of the ACL 2013 Conference|accessdate = |doi = |pmid = |last2 = Bauer|first2 = John|last3 = Manning|first3 = Christopher|last4 = Ng|first4 = Andrew}}</ref> [[sentiment analysis]],<ref>{{Cite journal |url= http://nlp.stanford.edu/~socherr/EMNLP2013_RNTN.pdf|title = Recursive Deep Models for Semantic Compositionality Over a Sentiment Treebank|last = Socher|first = Richard|date = 2013 |accessdate = |doi = |pmid =}}</ref> information retrieval,<ref>{{Cite journal|last=Shen|first=Yelong|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Mesnil|first5=Gregoire|date=2014-11-01|title=A Latent Semantic Model with Convolutional-Pooling Structure for Information Retrieval|url=https://www.microsoft.com/en-us/research/publication/a-latent-semantic-model-with-convolutional-pooling-structure-for-information-retrieval/|journal=Microsoft Research}}</ref><ref>{{Cite journal|last=Huang|first=Po-Sen|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Acero|first5=Alex|last6=Heck|first6=Larry|date=2013-10-01|title=Learning Deep Structured Semantic Models for Web Search using Clickthrough Data|url=https://www.microsoft.com/en-us/research/publication/learning-deep-structured-semantic-models-for-web-search-using-clickthrough-data/|journal=Microsoft Research}}</ref> spoken language understanding,<ref name="IEEE-TASL2015">{{cite journal | last1 = Mesnil | first1 = G. | last2 = Dauphin | first2 = Y. | last3 = Yao | first3 = K. | last4 = Bengio | first4 = Y. | last5 = Deng | first5 = L. | last6 = Hakkani-Tur | first6 = D. | last7 = He | first7 = X. | last8 = Heck | first8 = L. | last9 = Tur | first9 = G. | last10 = Yu | first10 = D. | last11 = Zweig | first11 = G. | year = 2015 | title = Using recurrent neural networks for slot filling in spoken language understanding | url= https://www.semanticscholar.org/paper/41911ef90a225a82597a2b576346759ea9c34247| journal = IEEE Transactions on Audio, Speech, and Language Processing | volume = 23 | issue = 3| pages = 530–539 | doi=10.1109/taslp.2014.2383614}}</ref> machine translation,<ref name="NIPS2014">{{Cite journal|last=Sutskever|first=L.|last2=Vinyals|first2=O.|last3=Le|first3=Q.|date=2014|title=Sequence to Sequence Learning with Neural Networks|url=https://papers.nips.cc/paper/5346-sequence-to-sequence-learning-with-neural-networks.pdf|journal=Proc. NIPS|pages=|via=|bibcode=2014arXiv1409.3215S|arxiv=1409.3215}}</ref><ref name="auto">{{Cite journal|last=Gao|first=Jianfeng|last2=He|first2=Xiaodong|last3=Yih|first3=Scott Wen-tau|last4=Deng|first4=Li|date=2014-06-01|title=Learning Continuous Phrase Representations for Translation Modeling|url=https://www.microsoft.com/en-us/research/publication/learning-continuous-phrase-representations-for-translation-modeling/|journal=Microsoft Research}}</ref> contextual entity linking,<ref name="auto"/> writing style recognition,<ref name="BROC2017">{{Cite journal |doi = 10.1002/dac.3259|title = Authorship verification using deep belief network systems|journal = International Journal of Communication Systems|volume = 30|issue = 12|pages = e3259|year = 2017|last1 = Brocardo|first1 = Marcelo Luiz|last2 = Traore|first2 = Issa|last3 = Woungang|first3 = Isaac|last4 = Obaidat|first4 = Mohammad S.}}</ref> Text classification and others.<ref>{{Cite news|url=https://www.microsoft.com/en-us/research/project/deep-learning-for-natural-language-processing-theory-and-practice-cikm2014-tutorial/|title=Deep Learning for Natural Language Processing: Theory and Practice (CIKM2014 Tutorial) - Microsoft Research|work=Microsoft Research|accessdate=2017-06-14}}</ref>

Recent developments generalize [[word embedding]] to [[sentence embedding]].

[[Google Translate]] (GT) uses a large [[End-to-end principle|end-to-end]] long short-term memory network.<ref name="GT_Turovsky_2016">{{cite web|url=https://blog.google/products/translate/found-translation-more-accurate-fluent-sentences-google-translate/|title=Found in translation: More accurate, fluent sentences in Google Translate|last=Turovsky|first=Barak|date=November 15, 2016|website=The Keyword Google Blog|accessdate=March 23, 2017}}</ref><ref name="googleblog_GNMT_2016">{{cite web|url=https://research.googleblog.com/2016/11/zero-shot-translation-with-googles.html|title=Zero-Shot Translation with Google's Multilingual Neural Machine Translation System|last1=Schuster|first1=Mike|last2=Johnson|first2=Melvin|date=November 22, 2016|website=Google Research Blog|accessdate=March 23, 2017|last3=Thorat|first3=Nikhil}}</ref><ref name="lstm1997">{{Cite journal|author=Sepp Hochreiter|author2=Jürgen Schmidhuber|year=1997|title=Long short-term memory|url=https://www.researchgate.net/publication/13853244|journal=[[Neural Computation (journal)|Neural Computation]]|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|pmid=9377276|via=}}</ref><ref name="lstm2000">{{Cite journal|author=Felix A. Gers|author2=Jürgen Schmidhuber|author3=Fred Cummins|year=2000|title=Learning to Forget: Continual Prediction with LSTM|journal=[[Neural Computation (journal)|Neural Computation]]|volume=12|issue=10|pages=2451–2471|doi=10.1162/089976600300015015|pmid=11032042|citeseerx=10.1.1.55.5709|url=https://www.semanticscholar.org/paper/11540131eae85b2e11d53df7f1360eeb6476e7f4}}</ref><ref name="GoogleTranslate">{{cite arXiv |eprint=1609.08144|last1=Wu|first1=Yonghui|title=Google's Neural Machine Translation System: Bridging the Gap between Human and Machine Translation|last2=Schuster|first2=Mike|last3=Chen|first3=Zhifeng|last4=Le|first4=Quoc V|last5=Norouzi|first5=Mohammad|last6=Macherey|first6=Wolfgang|last7=Krikun|first7=Maxim|last8=Cao|first8=Yuan|last9=Gao|first9=Qin|last10=Macherey|first10=Klaus|last11=Klingner|first11=Jeff|last12=Shah|first12=Apurva|last13=Johnson|first13=Melvin|last14=Liu|first14=Xiaobing|last15=Kaiser|first15=Łukasz|last16=Gouws|first16=Stephan|last17=Kato|first17=Yoshikiyo|last18=Kudo|first18=Taku|last19=Kazawa|first19=Hideto|last20=Stevens|first20=Keith|last21=Kurian|first21=George|last22=Patil|first22=Nishant|last23=Wang|first23=Wei|last24=Young|first24=Cliff|last25=Smith|first25=Jason|last26=Riesa|first26=Jason|last27=Rudnick|first27=Alex|last28=Vinyals|first28=Oriol|last29=Corrado|first29=Greg|last30=Hughes|first30=Macduff|display-authors=29|class=cs.CL|year=2016}}</ref><ref name="WiredGoogleTranslate">"An Infusion of AI Makes Google Translate More Powerful Than Ever." Cade Metz, WIRED, Date of Publication: 09.27.16. https://www.wired.com/2016/09/google-claims-ai-breakthrough-machine-translation/</ref> [[Google Neural Machine Translation|Google Neural Machine Translation (GNMT)]] uses an [[example-based machine translation]] method in which the system "learns from millions of examples."<ref name="googleblog_GNMT_2016" /> It translates "whole sentences at a time, rather than pieces. Google Translate supports over one hundred languages.<ref name="googleblog_GNMT_2016" /> The network encodes the "semantics of the sentence rather than simply memorizing phrase-to-phrase translations".<ref name="googleblog_GNMT_2016" /><ref name="Biotet">{{cite web|url=http://www-clips.imag.fr/geta/herve.blanchon/Pdfs/NLP-KE-10.pdf|title=MT on and for the Web|last1=Boitet|first1=Christian|last2=Blanchon|first2=Hervé|date=2010|accessdate=December 1, 2016|last3=Seligman|first3=Mark|last4=Bellynck|first4=Valérie}}</ref> GT uses English as an intermediate between most language pairs.<ref name="Biotet" />

=== Drug discovery and toxicology ===
{{For|more information|Drug discovery|Toxicology}}
A large percentage of candidate drugs fail to win regulatory approval. These failures are caused by insufficient efficacy (on-target effect), undesired interactions (off-target effects), or unanticipated [[Toxicity|toxic effects]].<ref name="ARROWSMITH2013">{{Cite journal
| pmid = 23903212
| year = 2013
| last1 = Arrowsmith
| first1 = J
| title = Trial watch: Phase II and phase III attrition rates 2011-2012
| journal = Nature Reviews Drug Discovery
| volume = 12
| issue = 8
| pages = 569
| last2 = Miller
| first2 = P
| doi = 10.1038/nrd4090
| url = https://www.semanticscholar.org/paper/9ab0f468a64762ca5069335c776e1ab07fa2b3e2
}}</ref><ref name="VERBIEST2015">{{Cite journal
| pmid = 25582842
| year = 2015
| last1 = Verbist
| first1 = B
| title = Using transcriptomics to guide lead optimization in drug discovery projects: Lessons learned from the QSTAR project
| journal = Drug Discovery Today
| last2 = Klambauer
| first2 = G
| last3 = Vervoort
| first3 = L
| last4 = Talloen
| first4 = W
| last5 = The Qstar
| first5 = Consortium
| last6 = Shkedy
| first6 = Z
| last7 = Thas
| first7 = O
| last8 = Bender
| first8 = A
| last9 = Göhlmann
| first9 = H. W.
| last10 = Hochreiter
| first10 = S
| doi = 10.1016/j.drudis.2014.12.014
| volume=20
| issue = 5
| pages=505–513
}}</ref> Research has explored use of deep learning to predict the [[biomolecular target]]s,<ref name="MERCK2012" /><ref name=":5" /> [[off-target]]s, and [[Toxicity|toxic effects]] of environmental chemicals in nutrients, household products and drugs.<ref name="TOX21" /><ref name="TOX21Data" /><ref name=":11" />

AtomNet is a deep learning system for structure-based [[Drug design|rational drug design]].<ref>{{cite arXiv|title = AtomNet: A Deep Convolutional Neural Network for Bioactivity Prediction in Structure-based Drug Discovery|eprint= 1510.02855|date = 2015-10-09|first = Izhar|last = Wallach|first2 = Michael|last2 = Dzamba|first3 = Abraham|last3 = Heifets|class= cs.LG}}</ref> AtomNet was used to predict novel candidate biomolecules for disease targets such as the [[Ebola virus]]<ref>{{Cite news|title = Toronto startup has a faster way to discover effective medicines |url= https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/|website = The Globe and Mail |accessdate= 2015-11-09}}</ref> and [[multiple sclerosis]].<ref>{{Cite web|title = Startup Harnesses Supercomputers to Seek Cures |url= http://ww2.kqed.org/futureofyou/2015/05/27/startup-harnesses-supercomputers-to-seek-cures/|website = KQED Future of You|accessdate = 2015-11-09}}</ref><ref>{{cite web|url=https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/%5D%20and%20multiple%20sclerosis%20%5B/|title=Toronto startup has a faster way to discover effective medicines}}</ref>

In 2019 generative neural networks were used to produce molecules that were validated experimentally all the way into mice.<ref>{{cite journal |last1=Zhavoronkov |first1=Alex|date=2019|title=Deep learning enables rapid identification of potent DDR1 kinase inhibitors |journal=Nature Biotechnology |volume=37|issue=9|pages=1038–1040|doi=10.1038/s41587-019-0224-x |pmid=31477924|url=https://www.semanticscholar.org/paper/d44ac0a7fd4734187bccafc4a2771027b8bb595e}}</ref><ref>{{cite journal |last1=Gregory |first1=Barber |title=A Molecule Designed By AI Exhibits 'Druglike' Qualities |url=https://www.wired.com/story/molecule-designed-ai-exhibits-druglike-qualities/ |journal=Wired}}</ref>

=== Customer relationship management ===
{{Main|Customer relationship management}}
Deep reinforcement learning has been used to approximate the value of possible [[direct marketing]] actions, defined in terms of [[RFM (customer value)|RFM]] variables. The estimated value function was shown to have a natural interpretation as [[customer lifetime value]].<ref>{{cite arxiv|last=Tkachenko |first=Yegor |title=Autonomous CRM Control via CLV Approximation with Deep Reinforcement Learning in Discrete and Continuous Action Space |date=April 8, 2015 |eprint=1504.01840|class=cs.LG }}</ref>

=== Recommendation systems ===
{{Main|Recommender system}}
Recommendation systems have used deep learning to extract meaningful features for a latent factor model for content-based music and journal recommendations.<ref>{{Cite book|url=http://papers.nips.cc/paper/5004-deep-content-based-music-recommendation.pdf|title=Advances in Neural Information Processing Systems 26|last=van den Oord|first=Aaron|last2=Dieleman|first2=Sander|last3=Schrauwen|first3=Benjamin|date=2013|publisher=Curran Associates, Inc.|editor-last=Burges|editor-first=C. J. C.|pages=2643–2651|editor-last2=Bottou|editor-first2=L.|editor-last3=Welling|editor-first3=M.|editor-last4=Ghahramani|editor-first4=Z.|editor-last5=Weinberger|editor-first5=K. Q.}}</ref><ref>X.Y. Feng, H. Zhang, Y.J. Ren, P.H. Shang, Y. Zhu, Y.C. Liang, R.C. Guan, D. Xu, (2019), "[https://www.jmir.org/2019/5/e12957/ The Deep Learning–Based Recommender System “Pubmender” for Choosing a Biomedical Publication Venue: Development and Validation Study]", ''[[Journal of Medical Internet Research]]'', 21 (5): e12957</ref> Multiview deep learning has been applied for learning user preferences from multiple domains.<ref>{{Cite journal|last=Elkahky|first=Ali Mamdouh|last2=Song|first2=Yang|last3=He|first3=Xiaodong|date=2015-05-01|title=A Multi-View Deep Learning Approach for Cross Domain User Modeling in Recommendation Systems|url=https://www.microsoft.com/en-us/research/publication/a-multi-view-deep-learning-approach-for-cross-domain-user-modeling-in-recommendation-systems/|journal=Microsoft Research}}</ref> The model uses a hybrid collaborative and content-based approach and enhances recommendations in multiple tasks.

=== Bioinformatics ===
{{Main|Bioinformatics}}
An [[autoencoder]] ANN was used in [[bioinformatics]], to predict [[Gene Ontology|gene ontology]] annotations and gene-function relationships.<ref>{{cite book|title=Deep Autoencoder Neural Networks for Gene Ontology Annotation Predictions |first1=Davide |last1=Chicco|first2=Peter|last2=Sadowski|first3=Pierre |last3=Baldi |date=1 January 2014|publisher=ACM|pages=533–540|doi=10.1145/2649387.2649442|journal=Proceedings of the 5th ACM Conference on Bioinformatics, Computational Biology, and Health Informatics - BCB '14|isbn=9781450328944 |hdl = 11311/964622|url=https://www.semanticscholar.org/paper/09f3132fdf103bdef1125ffbccb8b46f921b2ab7 }}</ref>

In medical informatics, deep learning was used to predict sleep quality based on data from wearables<ref>{{Cite journal|last=Sathyanarayana|first=Aarti|date=2016-01-01|title=Sleep Quality Prediction From Wearable Data Using Deep Learning|journal=JMIR mHealth and uHealth|volume=4|issue=4|doi=10.2196/mhealth.6562|pmid=27815231|pmc=5116102|pages=e125|url=https://www.semanticscholar.org/paper/c82884f9d6d39c8a89ac46b8f688669fb2931144}}</ref> and predictions of health complications from [[electronic health record]] data.<ref>{{Cite journal|last=Choi|first=Edward|last2=Schuetz|first2=Andy|last3=Stewart|first3=Walter F.|last4=Sun|first4=Jimeng|date=2016-08-13|title=Using recurrent neural network models for early detection of heart failure onset|url=http://jamia.oxfordjournals.org/content/early/2016/08/13/jamia.ocw112|journal=Journal of the American Medical Informatics Association|volume=24|issue=2|pages=361–370|doi=10.1093/jamia/ocw112|issn=1067-5027|pmid=27521897|pmc=5391725}}</ref> Deep learning has also showed efficacy in [[Artificial intelligence in healthcare|healthcare]].<ref>{{Cite web|url=https://medium.com/the-mission/deep-learning-in-healthcare-challenges-and-opportunities-d2eee7e2545|title=Deep Learning in Healthcare: Challenges and Opportunities|date=2016-08-12|website=Medium|access-date=2018-04-10}}</ref>

=== Medical Image Analysis ===
Deep learning has been shown to produce competitive results in medical application such as cancer cell classification, lesion detection, organ segmentation and image enhancement<ref>{{Cite journal|last=Litjens|first=Geert|last2=Kooi|first2=Thijs|last3=Bejnordi|first3=Babak Ehteshami|last4=Setio|first4=Arnaud Arindra Adiyoso|last5=Ciompi|first5=Francesco|last6=Ghafoorian|first6=Mohsen|last7=van der Laak|first7=Jeroen A.W.M.|last8=van Ginneken|first8=Bram|last9=Sánchez|first9=Clara I.|date=December 2017|title=A survey on deep learning in medical image analysis|journal=Medical Image Analysis|volume=42|pages=60–88|doi=10.1016/j.media.2017.07.005|pmid=28778026|arxiv=1702.05747|bibcode=2017arXiv170205747L|url=https://www.semanticscholar.org/paper/2abde28f75a9135c8ed7c50ea16b7b9e49da0c09}}</ref><ref>{{Cite book |doi=10.1109/ICCVW.2017.18|isbn=9781538610343|chapter=Deep Convolutional Neural Networks for Detecting Cellular Changes Due to Malignancy|title=2017 IEEE International Conference on Computer Vision Workshops (ICCVW)|pages=82–89|year=2017|last1=Forslid|first1=Gustav|last2=Wieslander|first2=Hakan|last3=Bengtsson|first3=Ewert|last4=Wahlby|first4=Carolina|last5=Hirsch|first5=Jan-Michael|last6=Stark|first6=Christina Runow|last7=Sadanandan|first7=Sajith Kecheril|chapter-url=http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326160|url=https://www.semanticscholar.org/paper/6ae67bb4528bd5d922fd5a0c1a180ff1940f803c}}</ref>

=== Mobile advertising ===
Finding the appropriate mobile audience for [[mobile advertising]] is always challenging, since many data points must be considered and analyzed before a target segment can be created and used in ad serving by any ad server.<ref>{{cite book |doi=10.1109/CSCITA.2017.8066548 |isbn=978-1-5090-4381-1|chapter=Predicting the popularity of instagram posts for a lifestyle magazine using deep learning|title=2017 2nd International Conference on Communication Systems, Computing and IT Applications (CSCITA)|pages=174–177|year=2017|last1=De|first1=Shaunak|last2=Maity|first2=Abhishek|last3=Goel|first3=Vritti|last4=Shitole|first4=Sanjay|last5=Bhattacharya|first5=Avik|chapter-url=https://www.semanticscholar.org/paper/c4389f8a63a7be58e007c183a49e491141f9e204}}</ref> Deep learning has been used to interpret large, many-dimensioned advertising datasets. Many data points are collected during the request/serve/click internet advertising cycle. This information can form the basis of machine learning to improve ad selection.

=== Image restoration ===
Deep learning has been successfully applied to [[inverse problems]] such as [[denoising]], [[super-resolution]], [[inpainting]], and [[film colorization]].<ref>{{Cite web|url=https://blog.floydhub.com/colorizing-and-restoring-old-images-with-deep-learning/|title=Colorizing and Restoring Old Images with Deep Learning|date=2018-11-13|website=FloydHub Blog|language=en|access-date=2019-10-11}}</ref> These applications include learning methods such as "Shrinkage Fields for Effective Image Restoration"<ref>{{cite conference | url= http://research.uweschmidt.org/pubs/cvpr14schmidt.pdf |first1= Uwe |last1= Schmidt |first2= Stefan |last2= Roth |conference= Computer Vision and Pattern Recognition (CVPR), 2014 IEEE Conference on |title= Shrinkage Fields for Effective Image Restoration }}</ref> which trains on an image dataset, and [[Deep Image Prior]], which trains on the image that needs restoration.

=== Financial fraud detection ===
Deep learning is being successfully applied to financial [[fraud detection]] and anti-money laundering. "Deep anti-money laundering detection system can spot and recognize relationships and similarities between data and, further down the road, learn to detect anomalies or classify and predict specific events". The solution leverages both supervised learning techniques, such as the classification of suspicious transactions, and unsupervised learning, e.g. anomaly detection.
<ref>{{cite journal
|first=Tomasz |last=Czech
|title=Deep learning: the next frontier for money laundering detection
|url=https://www.globalbankingandfinance.com/deep-learning-the-next-frontier-for-money-laundering-detection/
|journal=Global Banking and Finance Review
}}</ref>

=== Military ===

The United States Department of Defense applied deep learning to train robots in new tasks through observation.<ref name=":12">{{Cite web|url=https://www.eurekalert.org/pub_releases/2018-02/uarl-ard020218.php|title=Army researchers develop new algorithms to train robots|website=EurekAlert!|access-date=2018-08-29}}</ref>

== Relation to human cognitive and brain development ==
Deep learning is closely related to a class of theories of [[brain development]] (specifically, neocortical development) proposed by [[cognitive neuroscientist]]s in the early 1990s.<ref name="UTGOFF">{{cite journal | last1 = Utgoff | first1 = P. E. | last2 = Stracuzzi | first2 = D. J. | year = 2002 | title = Many-layered learning | url= https://www.semanticscholar.org/paper/398c477f674b228fec7f3f418a8cec047e2dafe5| journal = Neural Computation | volume = 14 | issue = 10| pages = 2497–2529 | doi=10.1162/08997660260293319| pmid = 12396572 }}</ref><ref name="ELMAN">{{cite book|url={{google books |plainurl=y |id=vELaRu_MrwoC}}|title=Rethinking Innateness: A Connectionist Perspective on Development|last=Elman|first=Jeffrey L.|publisher=MIT Press|year=1998|isbn=978-0-262-55030-7}}</ref><ref name="SHRAGER">{{cite journal | last1 = Shrager | first1 = J. | last2 = Johnson | first2 = MH | year = 1996 | title = Dynamic plasticity influences the emergence of function in a simple cortical array | url= | journal = Neural Networks | volume = 9 | issue = 7| pages = 1119–1129 | doi=10.1016/0893-6080(96)00033-0| pmid = 12662587 }}</ref><ref name="QUARTZ">{{cite journal | last1 = Quartz | first1 = SR | last2 = Sejnowski | first2 = TJ | year = 1997 | title = The neural basis of cognitive development: A constructivist manifesto | url= | journal = Behavioral and Brain Sciences | volume = 20 | issue = 4| pages = 537–556 | doi=10.1017/s0140525x97001581| pmid = 10097006 | citeseerx = 10.1.1.41.7854 }}</ref> These developmental theories were instantiated in computational models, making them predecessors of deep learning systems. These developmental models share the property that various proposed learning dynamics in the brain (e.g., a wave of [[nerve growth factor]]) support the [[self-organization]] somewhat analogous to the neural networks utilized in deep learning models. Like the [[neocortex]], neural networks employ a hierarchy of layered filters in which each layer considers information from a prior layer (or the operating environment), and then passes its output (and possibly the original input), to other layers. This process yields a self-organizing stack of [[transducer]]s, well-tuned to their operating environment. A 1995 description stated, "...the infant's brain seems to organize itself under the influence of waves of so-called trophic-factors ... different regions of the brain become connected sequentially, with one layer of tissue maturing before another and so on until the whole brain is mature."<ref name="BLAKESLEE">S. Blakeslee., "In brain's early growth, timetable may be critical," ''The New York Times, Science Section'', pp. B5–B6, 1995.</ref>

A variety of approaches have been used to investigate the plausibility of deep learning models from a neurobiological perspective. On the one hand, several variants of the [[backpropagation]] algorithm have been proposed in order to increase its processing realism.<ref>{{Cite journal|last=Mazzoni|first=P.|last2=Andersen|first2=R. A.|last3=Jordan|first3=M. I.|date=1991-05-15|title=A more biologically plausible learning rule for neural networks.|journal=Proceedings of the National Academy of Sciences|volume=88|issue=10|pages=4433–4437|doi=10.1073/pnas.88.10.4433|issn=0027-8424|pmid=1903542|pmc=51674|bibcode=1991PNAS...88.4433M}}</ref><ref>{{Cite journal|last=O'Reilly|first=Randall C.|date=1996-07-01|title=Biologically Plausible Error-Driven Learning Using Local Activation Differences: The Generalized Recirculation Algorithm|journal=Neural Computation|volume=8|issue=5|pages=895–938|doi=10.1162/neco.1996.8.5.895|issn=0899-7667|url=https://www.semanticscholar.org/paper/ed9133009dd451bd64215cca7deba6e0b8d7c7b1}}</ref> Other researchers have argued that unsupervised forms of deep learning, such as those based on hierarchical [[generative model]]s and [[deep belief network]]s, may be closer to biological reality.<ref>{{Cite journal|last=Testolin|first=Alberto|last2=Zorzi|first2=Marco|date=2016|title=Probabilistic Models and Generative Neural Networks: Towards an Unified Framework for Modeling Normal and Impaired Neurocognitive Functions|journal=Frontiers in Computational Neuroscience|volume=10|pages=73|doi=10.3389/fncom.2016.00073|pmid=27468262|pmc=4943066|issn=1662-5188|url=https://www.semanticscholar.org/paper/9ff36a621ee2c831fbbda5b719942f9ed8ac844f}}</ref><ref>{{Cite journal|last=Testolin|first=Alberto|last2=Stoianov|first2=Ivilin|last3=Zorzi|first3=Marco|date=September 2017|title=Letter perception emerges from unsupervised deep learning and recycling of natural image features|journal=Nature Human Behaviour|volume=1|issue=9|pages=657–664|doi=10.1038/s41562-017-0186-2|pmid=31024135|issn=2397-3374|url=https://www.semanticscholar.org/paper/ec2463bd610dcb30d67681160e895761e2dde482}}</ref> In this respect, generative neural network models have been related to neurobiological evidence about sampling-based processing in the cerebral cortex.<ref>{{Cite journal|last=Buesing|first=Lars|last2=Bill|first2=Johannes|last3=Nessler|first3=Bernhard|last4=Maass|first4=Wolfgang|date=2011-11-03|title=Neural Dynamics as Sampling: A Model for Stochastic Computation in Recurrent Networks of Spiking Neurons|journal=PLOS Computational Biology|volume=7|issue=11|pages=e1002211|doi=10.1371/journal.pcbi.1002211|pmid=22096452|pmc=3207943|issn=1553-7358|bibcode=2011PLSCB...7E2211B|url=https://www.semanticscholar.org/paper/e4e100e44bf7618c7d96188605fd9870012bdb50}}</ref>

Although a systematic comparison between the human brain organization and the neuronal encoding in deep networks has not yet been established, several analogies have been reported. For example, the computations performed by deep learning units could be similar to those of actual neurons<ref>{{Cite journal|last=Morel|first=Danielle|last2=Singh|first2=Chandan|last3=Levy|first3=William B.|date=2018-01-25|title=Linearization of excitatory synaptic integration at no extra cost|journal=Journal of Computational Neuroscience|volume=44|issue=2|pages=173–188|doi=10.1007/s10827-017-0673-5|pmid=29372434|issn=0929-5313|url=https://www.semanticscholar.org/paper/3a528f2cde957d4e6417651f8005ca2ee81ca367}}</ref><ref>{{Cite journal|last=Cash|first=S.|last2=Yuste|first2=R.|date=February 1999|title=Linear summation of excitatory inputs by CA1 pyramidal neurons|journal=Neuron|volume=22|issue=2|pages=383–394|issn=0896-6273|pmid=10069343|doi=10.1016/s0896-6273(00)81098-3}}</ref> and neural populations.<ref>{{Cite journal|date=2004-08-01|title=Sparse coding of sensory inputs|journal=Current Opinion in Neurobiology|volume=14|issue=4|pages=481–487|doi=10.1016/j.conb.2004.07.007|pmid=15321069|issn=0959-4388 | last1 = Olshausen | first1 = B | last2 = Field | first2 = D|url=https://www.semanticscholar.org/paper/0dd289358b14f8176adb7b62bf2fb53ea62b3818}}</ref> Similarly, the representations developed by deep learning models are similar to those measured in the primate visual system<ref>{{Cite journal|last=Yamins|first=Daniel L K|last2=DiCarlo|first2=James J|date=March 2016|title=Using goal-driven deep learning models to understand sensory cortex|journal=Nature Neuroscience|volume=19|issue=3|pages=356–365|doi=10.1038/nn.4244|pmid=26906502|issn=1546-1726|url=https://www.semanticscholar.org/paper/94c4ba7246f781632aa68ca5b1acff0fdbb2d92f}}</ref> both at the single-unit<ref>{{Cite journal|last=Zorzi|first=Marco|last2=Testolin|first2=Alberto|date=2018-02-19|title=An emergentist perspective on the origin of number sense|journal=Phil. Trans. R. Soc. B|volume=373|issue=1740|pages=20170043|doi=10.1098/rstb.2017.0043|issn=0962-8436|pmid=29292348|pmc=5784047|url=https://www.semanticscholar.org/paper/c91db0c8349a78384f54c6a9a98370f5c9381b6c}}</ref> and at the population<ref>{{Cite journal|last=Güçlü|first=Umut|last2=van Gerven|first2=Marcel A. J.|date=2015-07-08|title=Deep Neural Networks Reveal a Gradient in the Complexity of Neural Representations across the Ventral Stream|journal=Journal of Neuroscience|volume=35|issue=27|pages=10005–10014|doi=10.1523/jneurosci.5023-14.2015|pmid=26157000|pmc=6605414|arxiv=1411.6422}}</ref> levels.

== Commercial activity ==
[[Facebook]]'s AI lab performs tasks such as [[Automatic image annotation|automatically tagging uploaded pictures]] with the names of the people in them.<ref name="METZ2013">{{cite magazine|first=C. |last=Metz |title=Facebook's 'Deep Learning' Guru Reveals the Future of AI |url=https://www.wired.com/wiredenterprise/2013/12/facebook-yann-lecun-qa/ |magazine=Wired |date=12 December 2013}}</ref>

Google's [[DeepMind Technologies]] developed a system capable of learning how to play [[Atari]] video games using only pixels as data input. In 2015 they demonstrated their [[AlphaGo]] system, which learned the game of [[Go (game)|Go]] well enough to beat a professional Go player.<ref>{{Cite web|title = Google AI algorithm masters ancient game of Go |url= http://www.nature.com/news/google-ai-algorithm-masters-ancient-game-of-go-1.19234|website = Nature News & Comment|accessdate = 2016-01-30}}</ref><ref>{{Cite journal|title = Mastering the game of Go with deep neural networks and tree search|journal = [[Nature (journal)|Nature]]| issn= 0028-0836|pages = 484–489|volume = 529|issue = 7587|doi = 10.1038/nature16961|pmid = 26819042|first1 = David|last1 = Silver|author-link1=David Silver (programmer)|first2 = Aja|last2 = Huang|author-link2=Aja Huang|first3 = Chris J.|last3 = Maddison|first4 = Arthur|last4 = Guez|first5 = Laurent|last5 = Sifre|first6 = George van den|last6 = Driessche|first7 = Julian|last7 = Schrittwieser|first8 = Ioannis|last8 = Antonoglou|first9 = Veda|last9 = Panneershelvam|first10= Marc|last10= Lanctot|first11= Sander|last11= Dieleman|first12=Dominik|last12= Grewe|first13= John|last13= Nham|first14= Nal|last14= Kalchbrenner|first15= Ilya|last15= Sutskever|author-link15=Ilya Sutskever|first16= Timothy|last16= Lillicrap|first17= Madeleine|last17= Leach|first18= Koray|last18= Kavukcuoglu|first19= Thore|last19= Graepel|first20= Demis |last20=Hassabis|author-link20=Demis Hassabis|date= 28 January 2016|bibcode = 2016Natur.529..484S|url = https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}{{closed access}}</ref><ref>{{Cite web|title = A Google DeepMind Algorithm Uses Deep Learning and More to Master the Game of Go {{!}} MIT Technology Review |url= http://www.technologyreview.com/news/546066/googles-ai-masters-the-game-of-go-a-decade-earlier-than-expected/|website = MIT Technology Review|accessdate = 2016-01-30}}</ref> [[Google Translate]] uses a neural network to translate between more than 100 languages.

In 2015, [[Blippar]] demonstrated a mobile [[augmented reality]] application that uses deep learning to recognize objects in real time.<ref>{{Cite web|title=Blippar Demonstrates New Real-Time Augmented Reality App|url=https://techcrunch.com/2015/12/08/blippar-demonstrates-new-real-time-augmented-reality-app/|website=TechCrunch}}</ref>

In 2017, Covariant.ai was launched, which focuses on integrating deep learning into factories.<ref>[https://www.nytimes.com/2017/11/06/technology/artificial-intelligence-start-up.html A.I. Researchers Leave Elon Musk Lab to Begin Robotics Start-Up]</ref>

As of 2008,<ref>{{Cite document|title=TAMER: Training an Agent Manually via Evaluative Reinforcement - IEEE Conference Publication|doi=10.1109/DEVLRN.2008.4640845}}</ref> researchers at [[University of Texas at Austin|The University of Texas at Austin]] (UT) developed a machine learning framework called Training an Agent Manually via Evaluative Reinforcement, or TAMER, which proposed new methods for robots or computer programs to learn how to perform tasks by interacting with a human instructor.<ref name=":12" /> First developed as TAMER, a new algorithm called Deep TAMER was later introduced in 2018 during a collaboration between [[U.S. Army Research Laboratory]] (ARL) and UT researchers. Deep TAMER used deep learning to provide a robot the ability to learn new tasks through observation.<ref name=":12" /> Using Deep TAMER, a robot learned a task with a human trainer, watching video streams or observing a human perform a task in-person. The robot later practiced the task with the help of some coaching from the trainer, who provided feedback such as “good job” and “bad job.”<ref>{{Cite web|url=https://governmentciomedia.com/talk-algorithms-ai-becomes-faster-learner|title=Talk to the Algorithms: AI Becomes a Faster Learner|website=governmentciomedia.com|access-date=2018-08-29}}</ref>

== Criticism and comment ==
Deep learning has attracted both criticism and comment, in some cases from outside the field of computer science.

=== Theory ===
{{see also|Explainable AI}}
A main criticism concerns the lack of theory surrounding some methods.<ref>{{Cite web|url=https://medium.com/@GaryMarcus/in-defense-of-skepticism-about-deep-learning-6e8bfd5ae0f1|title=In defense of skepticism about deep learning|last=Marcus|first=Gary|date=2018-01-14|website=Gary Marcus|access-date=2018-10-11}}</ref> Learning in the most common deep architectures is implemented using well-understood gradient descent. However, the theory surrounding other algorithms, such as contrastive divergence is less clear.{{citation needed|date=July 2016}} (e.g., Does it converge? If so, how fast? What is it approximating?) Deep learning methods are often looked at as a [[black box]], with most confirmations done empirically, rather than theoretically.<ref name="Knight 2017">{{cite web | last=Knight | first=Will | title=DARPA is funding projects that will try to open up AI's black boxes | website=MIT Technology Review | date=2017-03-14 | url=https://www.technologyreview.com/s/603795/the-us-military-wants-its-autonomous-machines-to-explain-themselves/ | accessdate=2017-11-02}}</ref>

Others point out that deep learning should be looked at as a step towards realizing strong AI, not as an all-encompassing solution. Despite the power of deep learning methods, they still lack much of the functionality needed for realizing this goal entirely. Research psychologist Gary Marcus noted:<blockquote>"Realistically, deep learning is only part of the larger challenge of building intelligent machines. Such techniques lack ways of representing [[causality|causal relationships]] (...) have no obvious ways of performing [[inference|logical inferences]], and they are also still a long way from integrating abstract knowledge, such as information about what objects are, what they are for, and how they are typically used. The most powerful A.I. systems, like [[Watson (computer)|Watson]] (...) use techniques like deep learning as just one element in a very complicated ensemble of techniques, ranging from the statistical technique of [[Bayesian inference]] to [[deductive reasoning]]."<ref>{{cite magazine|url=https://www.newyorker.com/|title=Is "Deep Learning" a Revolution in Artificial Intelligence?|last=Marcus|first=Gary|date=November 25, 2012|magazine=The New Yorker|accessdate=2017-06-14}}</ref></blockquote>As an alternative to this emphasis on the limits of deep learning, one author speculated that it might be possible to train a machine vision stack to perform the sophisticated task of discriminating between "old master" and amateur figure drawings, and hypothesized that such a sensitivity might represent the rudiments of a non-trivial machine empathy.<ref>{{cite web|url=http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|title=Art and Artificial Intelligence|date=March 27, 2015|publisher=ArtEnt|author=Smith, G. W.|accessdate=March 27, 2015|url-status=bot: unknown|archiveurl=https://web.archive.org/web/20170625075845/http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|archivedate=June 25, 2017}}</ref> This same author proposed that this would be in line with anthropology, which identifies a concern with aesthetics as a key element of [[behavioral modernity]].<ref>{{cite web |url=http://repositriodeficheiros.yolasite.com/resources/Texto%2028.pdf |author=Mellars, Paul |date=February 1, 2005 |title=The Impossible Coincidence: A Single-Species Model for the Origins of Modern Human Behavior in Europe|publisher=Evolutionary Anthropology: Issues, News, and Reviews |accessdate=April 5, 2017}}</ref>

In further reference to the idea that artistic sensitivity might inhere within relatively low levels of the cognitive hierarchy, a published series of graphic representations of the internal states of deep (20-30 layers) neural networks attempting to discern within essentially random data the images on which they were trained<ref>{{cite web|url=http://googleresearch.blogspot.co.uk/2015/06/inceptionism-going-deeper-into-neural.html |author1=Alexander Mordvintsev |author2=Christopher Olah |author3=Mike Tyka |date=June 17, 2015 |title=Inceptionism: Going Deeper into Neural Networks |publisher=Google Research Blog |accessdate=June 20, 2015}}</ref> demonstrate a visual appeal: the original research notice received well over 1,000 comments, and was the subject of what was for a time the most frequently accessed article on ''[[The Guardian]]'s''<ref>{{cite news|url=https://www.theguardian.com/technology/2015/jun/18/google-image-recognition-neural-network-androids-dream-electric-sheep|title=Yes, androids do dream of electric sheep|date=June 18, 2015|newspaper=The Guardian|author=Alex Hern|accessdate=June 20, 2015}}</ref> website.

=== Errors ===
Some deep learning architectures display problematic behaviors,<ref name=goertzel>{{cite web|first=Ben |last=Goertzel |title=Are there Deep Reasons Underlying the Pathologies of Today's Deep Learning Algorithms? |year=2015 |url=http://goertzel.org/DeepLearning_v1.pdf}}</ref> such as confidently classifying unrecognizable images as belonging to a familiar category of ordinary images<ref>{{cite arxiv |eprint=1412.1897|last1=Nguyen|first1=Anh|title=Deep Neural Networks are Easily Fooled: High Confidence Predictions for Unrecognizable Images|last2=Yosinski|first2=Jason|last3=Clune|first3=Jeff|class=cs.CV|year=2014}}</ref> and misclassifying minuscule perturbations of correctly classified images.<ref>{{cite arxiv |eprint=1312.6199|last1=Szegedy|first1=Christian|title=Intriguing properties of neural networks|last2=Zaremba|first2=Wojciech|last3=Sutskever|first3=Ilya|last4=Bruna|first4=Joan|last5=Erhan|first5=Dumitru|last6=Goodfellow|first6=Ian|last7=Fergus|first7=Rob|class=cs.CV|year=2013}}</ref> [[Ben Goertzel|Goertzel]] hypothesized that these behaviors are due to limitations in their internal representations and that these limitations would inhibit integration into heterogeneous multi-component [[artificial general intelligence]] (AGI) architectures.<ref name="goertzel" /> These issues may possibly be addressed by deep learning architectures that internally form states homologous to image-grammar<ref>{{cite journal | last1 = Zhu | first1 = S.C. | last2 = Mumford | first2 = D. | year = 2006| title = A stochastic grammar of images | url= | journal = Found. Trends Comput. Graph. Vis. | volume = 2 | issue = 4| pages = 259–362 | doi = 10.1561/0600000018| citeseerx = 10.1.1.681.2190 }}</ref> decompositions of observed entities and events.<ref name="goertzel"/> [[Grammar induction|Learning a grammar]] (visual or linguistic) from training data would be equivalent to restricting the system to [[commonsense reasoning]] that operates on concepts in terms of grammatical [[Production (computer science)|production rules]] and is a basic goal of both human language acquisition<ref>Miller, G. A., and N. Chomsky. "Pattern conception." Paper for Conference on pattern detection, University of Michigan. 1957.</ref> and [[artificial intelligence]] (AI).<ref>{{cite web|first=Jason |last=Eisner |title=Deep Learning of Recursive Structure: Grammar Induction |url=http://techtalks.tv/talks/deep-learning-of-recursive-structure-grammar-induction/58089/}}</ref>

=== Cyber threat ===
As deep learning moves from the lab into the world, research and experience shows that artificial neural networks are vulnerable to hacks and deception.<ref>{{Cite web|url=https://gizmodo.com/hackers-have-already-started-to-weaponize-artificial-in-1797688425|title=Hackers Have Already Started to Weaponize Artificial Intelligence|website=Gizmodo|access-date=2019-10-11}}</ref> By identifying patterns that these systems use to function, attackers can modify inputs to ANNs in such a way that the ANN finds a match that human observers would not recognize. For example, an attacker can make subtle changes to an image such that the ANN finds a match even though the image looks to a human nothing like the search target. Such a manipulation is termed an “adversarial attack.”<ref>{{Cite web|url=https://www.dailydot.com/debug/adversarial-attacks-ai-mistakes/|title=How hackers can force AI to make dumb mistakes|date=2018-06-18|website=The Daily Dot|language=en|access-date=2019-10-11}}</ref> In 2016 researchers used one ANN to doctor images in trial and error fashion, identify another's focal points and thereby generate images that deceived it. The modified images looked no different to human eyes. Another group showed that printouts of doctored images then photographed successfully tricked an image classification system.<ref name=":4">{{Cite news|url=https://singularityhub.com/2017/10/10/ai-is-easy-to-fool-why-that-needs-to-change|title=AI Is Easy to Fool—Why That Needs to Change|last=|first=|date=2017-10-10|work=Singularity Hub|accessdate=2017-10-11}}</ref> One defense is reverse image search, in which a possible fake image is submitted to a site such as [[TinEye]] that can then find other instances of it. A refinement is to search using only parts of the image, to identify images from which that piece may have been taken'''.'''<ref>{{Cite journal|last=Gibney|first=Elizabeth|title=The scientist who spots fake videos|url=https://www.nature.com/news/the-scientist-who-spots-fake-videos-1.22784|journal=Nature|pages=|doi=10.1038/nature.2017.22784|via=|year=2017}}</ref>

Another group showed that certain [[Psychedelic art|psychedelic]] spectacles could fool a [[facial recognition system]] into thinking ordinary people were celebrities, potentially allowing one person to impersonate another. In 2017 researchers added stickers to [[stop sign]]s and caused an ANN to misclassify them.<ref name=":4" />

ANNs can however be further trained to detect attempts at deception, potentially leading attackers and defenders into an arms race similar to the kind that already defines the [[malware]] defense industry. ANNs have been trained to defeat ANN-based anti-malware software by repeatedly attacking a defense with malware that was continually altered by a [[genetic algorithm]] until it tricked the anti-malware while retaining its ability to damage the target.<ref name=":4" />

Another group demonstrated that certain sounds could make the [[Google Now]] voice command system open a particular web address that would download malware.<ref name=":4" />

In “data poisoning,” false data is continually smuggled into a machine learning system's training set to prevent it from achieving mastery.<ref name=":4" />

=== Reliance on human [[microwork]] ===
Most Deep Learning systems rely on training and verification data that is generated and/or annotated by humans. It has been argued in [[Media studies|media philosophy]] that not only low-paid [[Clickworkers|clickwork]] (e.g. on [[Amazon Mechanical Turk]]) is regularly deployed for this purpose, but also implicit forms of human [[microwork]] that are often not recognized as such.<ref name=":13">{{Cite journal|last=Mühlhoff|first=Rainer|date=2019-11-06|title=Human-aided artificial intelligence: Or, how to run large computations in human brains? Toward a media sociology of machine learning|journal=New Media & Society|language=en|volume=|pages=146144481988533|doi=10.1177/1461444819885334|issn=1461-4448}}</ref> The philosopher Rainer Mühlhoff distinguishes five types of "machinic capture" of human microwork to generate training data: (1) [[gamification]] (the embedding of annotation or computation tasks in the flow of a game), (2) "trapping and tracking" (e.g. [[CAPTCHA]]s for image recognition or click-tracking on Google [[Search engine results page|search results pages]]), (3) exploitation of social motivations (e.g. [[Tag (Facebook)|tagging faces]] on [[Facebook]] to obtain labeled facial images), (4) [[information mining]] (e.g. by leveraging [[Quantified self|quantified-self]] devices such as [[activity tracker]]s) and (5) [[Clickworkers|clickwork]].<ref name=":13" /> Mühlhoff argues that in most commercial end-user applications of Deep Learning such as [[DeepFace|Facebook's face recognition system,]] the need for training data does not stop once an ANN is trained. Rather, there is a continued demand for human-generated verification data to constantly calibrate and update the ANN. For this purpose Facebook introduced the feature that once a user is automatically recognized in an image, they receive a notification. They can choose whether of not they like to be publicly labeled on the image, or tell Facebook that it is not them in the picture.<ref>{{Cite news|url=https://www.wired.com/story/facebook-will-find-your-face-even-when-its-not-tagged/|title=Facebook Can Now Find Your Face, Even When It's Not Tagged|work=Wired|access-date=2019-11-22|language=en|issn=1059-1028}}</ref> This user interface is a mechanism to generate "a constant stream of  verification data"<ref name=":13" /> to further train the network in real-time. As Mühlhoff argues, involvement of human users to generate training and verification data is so typical for most commercial end-user applications of Deep Learning that such systems may be referred to as "human-aided artificial intelligence".<ref name=":13" />

== Shallowing deep neural networks ==

{{technical|section|date=February 2020}}
Shallowing refers to reducing a pre-trained DNN to a smaller network with the same or similar performance.<ref>{{cite journal |last1= Chen|first1= S.|last2= Zhao|first2=Q.|date= 2018|title=Shallowing deep networks: Layer-wise pruning based on feature representations |url= |journal=Representations. IEEE Transactions on Pattern Analysis and Machine Intelligence |volume= 41|issue=12 |pages= 3048–56|doi=10.1109/TPAMI.2018.2874634 |pmid= 30296213|access-date=}}</ref> Training of DNN with further shallowing can produce more efficient systems than just training of smaller networks from scratch. Shallowing is the rebirth of pruning that developed in the 1980-1990s.<ref name= "Hassibi1993">{{cite conference
| url =
| title = Optimal brain surgeon and general network pruning
| last1 = Hassibi
| first1 = B.
| last2 = Stork
| first2 = D. G.
| last3 = Wolff
| first3 = G. J.
| date = 1993
| publisher = IEEE
| book-title = IEEE International Conference on Neural Networks
| pages = 293–299
| volume = 1
| location = San Francisco, CA, USA
| doi = 10.1109/ICNN.1993.298572
}}</ref><ref name= "Gordienko1993">
{{cite conference
| url =
| title = Construction of efficient neural networks: algorithms and tests
| last1 = Gordienko
| first1 = P.
| date = 1993
| publisher = IEEE
| book-title = Proceedings of 1993 International Conference on Neural Networks (IJCNN-93)
| pages = 313–6
| volume = 1
| location = Nagoya, Japan
| doi = 10.1109/IJCNN.1993.713920
}}</ref> The main approach to pruning is to gradually remove network elements (synapses, neurons, blocks of neurons, or layers) that have little impact on performance evaluation. Various indicators of sensitivity are used that estimate the changes of performance after pruning. The simplest indicators use just values of transmitted signals and the synaptic weights (the zeroth order). More complex indicators use mean absolute values of partial derivatives of the cost function,<ref name= "Gordienko1993"/><ref name="GorbMirTsar1999">{{cite conference
| url =
| title = Generation of explicit knowledge from empirical data through pruning of trainable neural networks
| last1 = Gorban
| first1 = A. N.
| last2 = Mirkes
| first2 = E. M.
| last3 = Tsaregorodtsev
| first3 = V. G.
| date = 1999
| publisher = IEEE
| book-title = IJCNN'99. International Joint Conference on Neural Networks. Proceedings (Cat. No.99CH36339)
| pages = 4393–4398
| location = Washington, DC, USA
| doi = 10.1109/IJCNN.1999.830876
| arxiv = cond-mat/0307083
}}</ref>
or even the second derivatives.<ref name= "Hassibi1993"/> The shallowing allows to reduce the necessary resources and makes the skills of neural network more explicit.<ref name="GorbMirTsar1999"/> It is used for image classification,<ref>{{cite journal |last1=Zhong |first1= G.|last2= Yan|first2= S.|last3= Huang|first3= K.|last4=Cai|first4=Y.|last5=Dong |first5= J.|date=2018|title= Reducing and stretching deep convolutional activation features for accurate image classification|url= |journal= Cogn. Comput.|volume= 10|issue= 1|pages=179–86|doi=10.1007/s12559-017-9515-z |access-date=}}</ref> for development of security systems,<ref name="MirkesDog2019">{{cite journal |last1=Gorban |first1= A. N.|last2=Mirkes |first2=E. M. |last3=Tyukin |first3= I. Y.|date= 2019|title=How deep should be the depth of convolutional neural networks: A backyard dog case study |url= |journal=Cogn. Comput.|volume= |issue= |pages= |doi= 10.1007/s12559-019-09667-7 | doi-access= free| arxiv= 1805.01516 }}</ref> for accelerating DNN execution on mobile devices,<ref>{{cite conference
| url = https://www.aaai.org/ocs/index.php/AAAI/AAAI18/paper/viewFile/16652/15946
| title = DeepRebirth: Accelerating deep neural network execution on mobile devices
| last1 = Li
| first1 = D.
| last2 = Wang
| first2 = X.
| last3 = Kong
| first3 = D.
| date = 2018
| publisher = Association for the Advancement of Artificial Intelligence
| book-title = Thirty-second AAAI conference on artificial intelligence (AAAI-18)
| pages =
| location =
| doi =
| arxiv = 1708.04728
}}
</ref> and for other applications. It has been demonstrated that using linear postprocessing, such as supervised PCA, improves DNN performance after shallowing.<ref name="MirkesDog2019"/>

== See also ==
* [[Applications of artificial intelligence]]
* [[Comparison of deep learning software]]
* [[Compressed sensing]]
* [[Echo state network]]
* [[List of artificial intelligence projects]]
* [[Liquid state machine]]
* [[List of datasets for machine learning research]]
* [[Reservoir computing]]
* [[Sparse coding]]

== References ==
{{Reflist|30em}}

== Further reading ==
{{refbegin}}
* {{cite book |title=Deep Learning |year=2016
|first1=Ian |last1=Goodfellow |authorlink1=Ian Goodfellow
|first2=Yoshua |last2=Bengio |authorlink2=Yoshua Bengio
|first3=Aaron |last3=Courville
|publisher=MIT Press
|url=http://www.deeplearningbook.org
|isbn=978-0-26203561-3
|postscript=, introductory textbook.
}}

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[[Category:Deep learning| ]]
[[Category:Artificial neural networks]]
[[Category:Artificial intelligence]]
[[Category:Emerging technologies]]

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'{{About||deep versus shallow learning in educational psychology|Student approaches to learning|more information|Artificial neural network}} {{short description|Branch of machine learning}} {{machine learning bar}} '''Deep learning''' (also known as '''deep structured learning''' or '''differential programming''') is part of a broader family of [[machine learning]] methods based on [[artificial neural networks]] with [[representation learning]]. Learning can be [[Supervised learning|supervised]], [[Semi-supervised learning|semi-supervised]] or [[Unsupervised learning|unsupervised]].<ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="NatureBengio">{{cite journal |last1=Bengio |first1=Yoshua |last2=LeCun |first2= Yann| last3=Hinton | first3= Geoffrey|year=2015 |title=Deep Learning |journal=Nature |volume=521 |issue=7553 |pages=436–444 |doi=10.1038/nature14539 |pmid=26017442|bibcode=2015Natur.521..436L |url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256 }}</ref> Deep learning architectures such as [[#Deep_neural_networks|deep neural network]]s, [[deep belief network]]s, [[recurrent neural networks]] and [[convolutional neural networks]] have been applied to fields including [[computer vision]], [[automatic speech recognition|speech recognition]], [[natural language processing]], [[audio recognition]], social network filtering, [[machine translation]], [[bioinformatics]], [[drug design]], medical image analysis, material inspection and [[board game]] programs, where they have produced results comparable to and in some cases surpassing human expert performance.<ref name=":9">{{Cite book |doi=10.1109/cvpr.2012.6248110 |isbn=978-1-4673-1228-8|arxiv=1202.2745|chapter=Multi-column deep neural networks for image classification|title=2012 IEEE Conference on Computer Vision and Pattern Recognition|pages=3642–3649|year=2012|last1=Ciresan|first1=D.|last2=Meier|first2=U.|last3=Schmidhuber|first3=J.}}</ref><ref name="krizhevsky2012">{{cite journal|last1=Krizhevsky|first1=Alex|last2=Sutskever|first2=Ilya|last3=Hinton|first3=Geoffry|date=2012|title=ImageNet Classification with Deep Convolutional Neural Networks|url=https://www.cs.toronto.edu/~kriz/imagenet_classification_with_deep_convolutional.pdf|journal=NIPS 2012: Neural Information Processing Systems, Lake Tahoe, Nevada}} </ref><ref>{{cite web |title=Google's AlphaGo AI wins three-match series against the world's best Go player |url=https://techcrunch.com/2017/05/24/alphago-beats-planets-best-human-go-player-ke-jie/amp/ |website=TechCrunch |date=25 May 2017}}</ref> [[Artificial neural network]]s (ANNs) were inspired by information processing and distributed communication nodes in biological systems. ANNs have various differences from biological [[brain]]s. Specifically, neural networks tend to be static and symbolic, while the biological brain of most living organisms is dynamic (plastic) and analog.<ref>{{Cite journal|last=Marblestone|first=Adam H.|last2=Wayne|first2=Greg|last3=Kording|first3=Konrad P.|date=2016|title=Toward an Integration of Deep Learning and Neuroscience |journal=Frontiers in Computational Neuroscience |volume=10|pages=94|doi=10.3389/fncom.2016.00094 |pmc=5021692|pmid=27683554|bibcode=2016arXiv160603813M|arxiv=1606.03813|url=https://www.semanticscholar.org/paper/2dec4f52b1ce552b416f086d4ea1040626675dfa}}</ref><ref>{{cite journal|last1=Olshausen|first1=B. A.|year=1996|title=Emergence of simple-cell receptive field properties by learning a sparse code for natural images|journal=Nature|volume=381|issue=6583|pages=607–609|bibcode=1996Natur.381..607O|doi=10.1038/381607a0|pmid=8637596|url=https://www.semanticscholar.org/paper/8012c4a1e2ca663f1a04e80cbb19631a00cbab27}}</ref><ref>{{cite arxiv|last=Bengio|first=Yoshua|last2=Lee|first2=Dong-Hyun|last3=Bornschein|first3=Jorg|last4=Mesnard|first4=Thomas|last5=Lin|first5=Zhouhan|date=2015-02-13|title=Towards Biologically Plausible Deep Learning|eprint=1502.04156|class=cs.LG}}</ref> {{toclimit|3}} == Definition == [[File:Deep Learning.jpg|alt=Representing Images on Multiple Layers of Abstraction in Deep Learning|thumb|Representing Images on Multiple Layers of Abstraction in Deep Learning <ref>{{Cite journal|last=Schulz|first=Hannes|last2=Behnke|first2=Sven|date=2012-11-01|title=Deep Learning|journal=KI - Künstliche Intelligenz|language=en|volume=26|issue=4|pages=357–363|doi=10.1007/s13218-012-0198-z|issn=1610-1987|url=https://www.semanticscholar.org/paper/51a80649d16a38d41dbd20472deb3bc9b61b59a0}}</ref>]] Deep learning is a class of [[machine learning]] [[algorithm]]s that<ref name="BOOK2014">{{cite journal|last2=Yu|first2=D.|year=2014|title=Deep Learning: Methods and Applications|url=http://research.microsoft.com/pubs/209355/DeepLearning-NowPublishing-Vol7-SIG-039.pdf|journal=Foundations and Trends in Signal Processing|volume=7|issue=3–4|pages=1–199|doi=10.1561/2000000039|last1=Deng|first1=L.}}</ref>{{rp|pages=199–200}} uses multiple layers to progressively extract higher level features from the raw input. For example, in [[image processing]], lower layers may identify edges, while higher layers may identify the concepts relevant to a human such as digits or letters or faces. == Overview == Most modern deep learning models are based on artificial neural networks, specifically, [[Convolutional Neural Network]]s (CNN)s, although they can also include [[propositional formula]]s or latent variables organized layer-wise in deep [[generative model]]s such as the nodes in [[deep belief network]]s and deep [[Boltzmann machine]]s.<ref name="BENGIODEEP">{{cite journal|last=Bengio|first=Yoshua|year=2009|title=Learning Deep Architectures for AI|url=http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20%282009%29.pdf|journal=Foundations and Trends in Machine Learning|volume=2|issue=1|pages=1–127|doi=10.1561/2200000006|citeseerx=10.1.1.701.9550|access-date=2015-09-03|archive-url=https://web.archive.org/web/20160304084250/http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20(2009).pdf|archive-date=2016-03-04|url-status=dead}}</ref> In deep learning, each level learns to transform its input data into a slightly more abstract and composite representation. In an image recognition application, the raw input may be a [[Matrix (mathematics)|matrix]] of pixels; the first representational layer may abstract the pixels and encode edges; the second layer may compose and encode arrangements of edges; the third layer may encode a nose and eyes; and the fourth layer may recognize that the image contains a face. Importantly, a deep learning process can learn which features to optimally place in which level ''on its own''. (Of course, this does not completely eliminate the need for hand-tuning; for example, varying numbers of layers and layer sizes can provide different degrees of abstraction.)<ref name="BENGIO2012">{{cite journal|last2=Courville|first2=A.|last3=Vincent|first3=P.|year=2013|title=Representation Learning: A Review and New Perspectives|journal=IEEE Transactions on Pattern Analysis and Machine Intelligence|volume=35|issue=8|pages=1798–1828|arxiv=1206.5538|doi=10.1109/tpami.2013.50|pmid=23787338|last1=Bengio|first1=Y.}}</ref><ref>{{cite journal|last1=LeCun|first1=Yann|last2=Bengio|first2=Yoshua|last3=Hinton|first3=Geoffrey|title=Deep learning|journal=Nature|date=28 May 2015|volume=521|issue=7553|pages=436–444|doi=10.1038/nature14539|pmid=26017442|bibcode=2015Natur.521..436L|url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256}}</ref> The word "deep" in "deep learning" refers to the number of layers through which the data is transformed. More precisely, deep learning systems have a substantial ''credit assignment path'' (CAP) depth. The CAP is the chain of transformations from input to output. CAPs describe potentially causal connections between input and output. For a [[feedforward neural network]], the depth of the CAPs is that of the network and is the number of hidden layers plus one (as the output layer is also parameterized). For [[recurrent neural network]]s, in which a signal may propagate through a layer more than once, the CAP depth is potentially unlimited.<ref name="SCHIDHUB" /> No universally agreed upon threshold of depth divides shallow learning from deep learning, but most researchers agree that deep learning involves CAP depth higher than 2. CAP of depth 2 has been shown to be a universal approximator in the sense that it can emulate any function.<ref>{{Cite book|url=https://books.google.com/books?id=9CqQDwAAQBAJ&pg=PA15&dq#v=onepage&q&f=false|title=Human Behavior and Another Kind in Consciousness: Emerging Research and Opportunities: Emerging Research and Opportunities|last=Shigeki|first=Sugiyama|date=2019-04-12|publisher=IGI Global|isbn=978-1-5225-8218-2|language=en}}</ref> Beyond that, more layers do not add to the function approximator ability of the network. Deep models (CAP > 2) are able to extract better features than shallow models and hence, extra layers help in learning the features effectively. Deep learning architectures can be constructed with a [[greedy algorithm|greedy]] layer-by-layer method.<ref name=BENGIO2007>{{cite conference | first1=Yoshua | last1=Bengio | first2=Pascal | last2=Lamblin | first3=Dan|last3=Popovici |first4=Hugo|last4=Larochelle | title=Greedy layer-wise training of deep networks| year=2007 | url=http://papers.nips.cc/paper/3048-greedy-layer-wise-training-of-deep-networks.pdf| conference = Advances in neural information processing systems | pages= 153–160}}</ref> Deep learning helps to disentangle these abstractions and pick out which features improve performance.<ref name="BENGIO2012" /> For [[supervised learning]] tasks, deep learning methods eliminate [[feature engineering]], by translating the data into compact intermediate representations akin to [[Principal Component Analysis|principal components]], and derive layered structures that remove redundancy in representation. Deep learning algorithms can be applied to unsupervised learning tasks. This is an important benefit because unlabeled data are more abundant than the labeled data. Examples of deep structures that can be trained in an unsupervised manner are neural history compressors<ref name="scholarpedia">Jürgen Schmidhuber (2015). Deep Learning. Scholarpedia, 10(11):32832. [http://www.scholarpedia.org/article/Deep_Learning Online]</ref> and [[deep belief network]]s.<ref name="BENGIO2012" /><ref name="SCHOLARDBNS">{{cite journal | last1 = Hinton | first1 = G.E. | year = 2009| title = Deep belief networks | url= | journal = Scholarpedia | volume = 4 | issue = 5| page = 5947 | doi=10.4249/scholarpedia.5947| bibcode = 2009SchpJ...4.5947H}}</ref> == Interpretations == Deep neural networks are generally interpreted in terms of the [[universal approximation theorem]]<ref name="ReferenceB">Balázs Csanád Csáji (2001). Approximation with Artificial Neural Networks; Faculty of Sciences; Eötvös Loránd University, Hungary</ref><ref name=cyb>{{cite journal | last1 = Cybenko | year = 1989 | title = Approximations by superpositions of sigmoidal functions | url = http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | journal = [[Mathematics of Control, Signals, and Systems]] | volume = 2 | issue = 4 | pages = 303–314 | doi = 10.1007/bf02551274 | url-status = dead | archiveurl = https://web.archive.org/web/20151010204407/http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | archivedate = 2015-10-10 }}</ref><ref name=horn>{{cite journal | last1 = Hornik | first1 = Kurt | year = 1991 | title = Approximation Capabilities of Multilayer Feedforward Networks | url= | journal = Neural Networks | volume = 4 | issue = 2| pages = 251–257 | doi=10.1016/0893-6080(91)90009-t}}</ref><ref name="Haykin, Simon 1998">{{cite book|first=Simon S. |last=Haykin|title=Neural Networks: A Comprehensive Foundation|url={{google books |plainurl=y |id=bX4pAQAAMAAJ}}|year=1999|publisher=Prentice Hall|isbn=978-0-13-273350-2}}</ref><ref name="Hassoun, M. 1995 p. 48">{{cite book|first=Mohamad H. |last=Hassoun|title=Fundamentals of Artificial Neural Networks|url={{google books |plainurl=y |id=Otk32Y3QkxQC|page=48}}|year=1995|publisher=MIT Press|isbn=978-0-262-08239-6|p=48}}</ref><ref name=ZhouLu>Lu, Z., Pu, H., Wang, F., Hu, Z., & Wang, L. (2017). [http://papers.nips.cc/paper/7203-the-expressive-power-of-neural-networks-a-view-from-the-width The Expressive Power of Neural Networks: A View from the Width]. Neural Information Processing Systems, 6231-6239. </ref> or [[Bayesian inference|probabilistic inference]].<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB">{{cite journal|last=Schmidhuber|first=J.|year=2015|title=Deep Learning in Neural Networks: An Overview|journal=Neural Networks|volume=61|pages=85–117|arxiv=1404.7828|doi=10.1016/j.neunet.2014.09.003|pmid=25462637|url=https://www.semanticscholar.org/paper/126df9f24e29feee6e49e135da102fbbd9154a48}}</ref><ref name="SCHOLARDBNS" /><ref name = MURPHY>{{cite book|first=Kevin P. |last=Murphy|title=Machine Learning: A Probabilistic Perspective|url={{google books |plainurl=y |id=NZP6AQAAQBAJ}}|date=24 August 2012|publisher=MIT Press|isbn=978-0-262-01802-9}}</ref><ref name= "Patel NIPS 2016">{{Cite journal|url=https://papers.nips.cc/paper/6231-a-probabilistic-framework-for-deep-learning.pdf|title=A Probabilistic Framework for Deep Learning|last=Patel|first=Ankit|last2=Nguyen|first2=Tan|last3=Baraniuk|first3=Richard|date=2016|journal=Advances in Neural Information Processing Systems|pages=|bibcode=2016arXiv161201936P|arxiv=1612.01936}}</ref> The classic universal approximation theorem concerns the capacity of [[feedforward neural networks]] with a single hidden layer of finite size to approximate [[continuous functions]].<ref name="ReferenceB"/><ref name="cyb"/><ref name="horn"/><ref name="Haykin, Simon 1998"/><ref name="Hassoun, M. 1995 p. 48"/> In 1989, the first proof was published by [[George Cybenko]] for [[sigmoid function|sigmoid]] activation functions<ref name="cyb" /> and was generalised to feed-forward multi-layer architectures in 1991 by Kurt Hornik.<ref name="horn" /> Recent work also showed that universal approximation also holds for non-bounded activation functions such as the rectified linear unit.<ref name=sonoda17>{{cite journal | last1 = Sonoda | first1 = Sho | last2=Murata | first2=Noboru | year = 2017 | title = Neural network with unbounded activation functions is universal approximator | journal = Applied and Computational Harmonic Analysis | volume = 43 | issue = 2 | pages = 233–268 | doi = 10.1016/j.acha.2015.12.005| arxiv = 1505.03654 | url = https://www.semanticscholar.org/paper/d0e48a4d5d6d0b4aa2dbab2c50560945e62a3817 }}</ref> The universal approximation theorem for [[deep neural network]]s concerns the capacity of networks with bounded width but the depth is allowed to grow. Lu et al.<ref name=ZhouLu/> proved that if the width of a [[deep neural network]] with [[ReLU]] activation is strictly larger than the input dimension, then the network can approximate any [[Lebesgue integration|Lebesgue integrable function]]; If the width is smaller or equal to the input dimension, then [[deep neural network]] is not a universal approximator. The [[probabilistic]] interpretation<ref name="MURPHY" /> derives from the field of [[machine learning]]. It features inference,<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="SCHOLARDBNS" /><ref name="MURPHY" /> as well as the [[optimization]] concepts of [[training]] and [[test (assessment)|testing]], related to fitting and [[generalization]], respectively. More specifically, the probabilistic interpretation considers the activation nonlinearity as a [[cumulative distribution function]].<ref name="MURPHY" /> The probabilistic interpretation led to the introduction of [[dropout (neural networks)|dropout]] as [[Regularization (mathematics)|regularizer]] in neural networks.<ref name="DROPOUT">{{cite arXiv |last1=Hinton |first1=G. E. |last2=Srivastava| first2 =N.|last3=Krizhevsky| first3=A.| last4 =Sutskever| first4=I.| last5=Salakhutdinov| first5=R.R.|eprint=1207.0580 |class=math.LG |title=Improving neural networks by preventing co-adaptation of feature detectors |date=2012}}</ref> The probabilistic interpretation was introduced by researchers including [[John Hopfield|Hopfield]], [[Bernard Widrow|Widrow]] and [[Kumpati S. Narendra|Narendra]] and popularized in surveys such as the one by [[Christopher Bishop|Bishop]].<ref name="prml">{{cite book|title=Pattern Recognition and Machine Learning|author=Bishop, Christopher M.|year=2006|publisher=Springer|url=http://users.isr.ist.utl.pt/~wurmd/Livros/school/Bishop%20-%20Pattern%20Recognition%20And%20Machine%20Learning%20-%20Springer%20%202006.pdf|isbn=978-0-387-31073-2}}</ref> == History == The term ''Deep Learning'' was introduced to the machine learning community by [[Rina Dechter]] in 1986,<ref name="dechter1986">[[Rina Dechter]] (1986). Learning while searching in constraint-satisfaction problems. University of California, Computer Science Department, Cognitive Systems Laboratory.[https://www.researchgate.net/publication/221605378_Learning_While_Searching_in_Constraint-Satisfaction-Problems Online]</ref><ref name="scholarpedia" /> and to [[Artificial Neural Networks|artificial neural networks]] by Igor Aizenberg and colleagues in 2000, in the context of [[Boolean network|Boolean]] threshold neurons.<ref name="aizenberg2000">Igor Aizenberg, Naum N. Aizenberg, Joos P.L. Vandewalle (2000). Multi-Valued and Universal Binary Neurons: Theory, Learning and Applications. Springer Science & Business Media.</ref><ref>Co-evolving recurrent neurons learn deep memory POMDPs. Proc. GECCO, Washington, D. C., pp. 1795-1802, ACM Press, New York, NY, USA, 2005.</ref> The first general, working learning algorithm for supervised, deep, feedforward, multilayer [[perceptron]]s was published by [[Alexey Ivakhnenko]] and Lapa in 1967.<ref name="ivak1965">{{cite book|first1=A. G. |last1=Ivakhnenko |first2=V. G. |last2=Lapa |title=Cybernetics and Forecasting Techniques|url={{google books |plainurl=y |id=rGFgAAAAMAAJ}}|year=1967|publisher=American Elsevier Publishing Co.|isbn=978-0-444-00020-0}}</ref> A 1971 paper described already a deep network with 8 layers trained by the [[group method of data handling]] algorithm.<ref name="ivak1971">{{Cite journal|last=Ivakhnenko|first=Alexey|date=1971|title=Polynomial theory of complex systems|url=http://gmdh.net/articles/history/polynomial.pdf |journal=IEEE Transactions on Systems, Man and Cybernetics |pages=364–378|doi=10.1109/TSMC.1971.4308320|pmid=|accessdate=|volume=SMC-1|issue=4}}</ref> Other deep learning working architectures, specifically those built for [[computer vision]], began with the [[Neocognitron]] introduced by [[Kunihiko Fukushima]] in 1980.<ref name="FUKU1980">{{cite journal | last1 = Fukushima | first1 = K. | year = 1980 | title = Neocognitron: A self-organizing neural network model for a mechanism of pattern recognition unaffected by shift in position | url= | journal = Biol. Cybern. | volume = 36 | issue = 4| pages = 193–202 | doi=10.1007/bf00344251 | pmid=7370364}}</ref> In 1989, [[Yann LeCun]] et al. applied the standard backpropagation algorithm, which had been around as the reverse mode of [[automatic differentiation]] since 1970,<ref name="lin1970">[[Seppo Linnainmaa]] (1970). The representation of the cumulative rounding error of an algorithm as a Taylor expansion of the local rounding errors. Master's Thesis (in Finnish), Univ. Helsinki, 6-7.</ref><ref name="grie2012">{{Cite journal|last=Griewank|first=Andreas|date=2012|title=Who Invented the Reverse Mode of Differentiation?|url=http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|journal=Documenta Mathematica|issue=Extra Volume ISMP|pages=389–400|access-date=2017-06-11|archive-url=https://web.archive.org/web/20170721211929/http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|archive-date=2017-07-21|url-status=dead}}</ref><ref name="WERBOS1974">{{Cite journal|last=Werbos|first=P.|date=1974|title=Beyond Regression: New Tools for Prediction and Analysis in the Behavioral Sciences |url=https://www.researchgate.net/publication/35657389 |journal=Harvard University |accessdate=12 June 2017}}</ref><ref name="werbos1982">{{Cite book|chapter-url=ftp://ftp.idsia.ch/pub/juergen/habilitation.pdf|title=System modeling and optimization|last=Werbos|first=Paul|publisher=Springer|year=1982|isbn=|location=|pages=762–770|chapter=Applications of advances in nonlinear sensitivity analysis}}</ref> to a deep neural network with the purpose of recognizing handwritten [[ZIP code]]s on mail. While the algorithm worked, training required 3 days.<ref name="LECUN1989">LeCun ''et al.'', "Backpropagation Applied to Handwritten Zip Code Recognition," ''Neural Computation'', 1, pp. 541–551, 1989.</ref> By 1991 such systems were used for recognizing isolated 2-D hand-written digits, while [[3D object recognition|recognizing 3-D objects]] was done by matching 2-D images with a handcrafted 3-D object model. Weng ''et al.'' suggested that a human brain does not use a monolithic 3-D object model and in 1992 they published Cresceptron,<ref name="Weng1992">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCNN1992.pdf Cresceptron: a self-organizing neural network which grows adaptively]," ''Proc. International Joint Conference on Neural Networks'', Baltimore, Maryland, vol I, pp. 576-581, June, 1992.</ref><ref name="Weng1993">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronICCV1993.pdf Learning recognition and segmentation of 3-D objects from 2-D images]," ''Proc. 4th International Conf. Computer Vision'', Berlin, Germany, pp. 121-128, May, 1993.</ref><ref name="Weng1997">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCV.pdf Learning recognition and segmentation using the Cresceptron]," ''International Journal of Computer Vision'', vol. 25, no. 2, pp. 105-139, Nov. 1997.</ref> a method for performing 3-D object recognition in cluttered scenes. Because it directly used natural images, Cresceptron started the beginning of general-purpose visual learning for natural 3D worlds. Cresceptron is a cascade of layers similar to Neocognitron. But while Neocognitron required a human programmer to hand-merge features, Cresceptron learned an open number of features in each layer without supervision, where each feature is represented by a [[Convolution|convolution kernel]]. Cresceptron segmented each learned object from a cluttered scene through back-analysis through the network. [[Max pooling]], now often adopted by deep neural networks (e.g. [[ImageNet]] tests), was first used in Cresceptron to reduce the position resolution by a factor of (2x2) to 1 through the cascade for better generalization. In 1994, André de Carvalho, together with Mike Fairhurst and David Bisset, published experimental results of a multi-layer boolean neural network, also known as a weightless neural network, composed of a 3-layers self-organising feature extraction neural network module (SOFT) followed by a multi-layer classification neural network module (GSN), which were independently trained. Each layer in the feature extraction module extracted features with growing complexity regarding the previous layer.<ref>{{Cite journal |title=An integrated Boolean neural network for pattern classification |journal=Pattern Recognition Letters |date=1994-08-08 |pages=807–813 |volume=15 |issue=8 |doi=10.1016/0167-8655(94)90009-4 |first=Andre C. L. F. |last1=de Carvalho |first2 = Mike C. |last2=Fairhurst |first3=David |last3 = Bisset}}</ref> In 1995, [[Brendan Frey]] demonstrated that it was possible to train (over two days) a network containing six fully connected layers and several hundred hidden units using the [[wake-sleep algorithm]], co-developed with [[Peter Dayan]] and [[Geoffrey Hinton|Hinton]].<ref>{{Cite journal|title = The wake-sleep algorithm for unsupervised neural networks |journal = Science|date = 1995-05-26|pages = 1158–1161|volume = 268|issue = 5214|doi = 10.1126/science.7761831|pmid = 7761831|first = Geoffrey E.|last = Hinton|first2 = Peter|last2 = Dayan|first3 = Brendan J.|last3 = Frey|first4 = Radford|last4 = Neal|bibcode = 1995Sci...268.1158H}}</ref> Many factors contribute to the slow speed, including the [[vanishing gradient problem]] analyzed in 1991 by [[Sepp Hochreiter]].<ref name="HOCH1991">S. Hochreiter., "[http://people.idsia.ch/~juergen/SeppHochreiter1991ThesisAdvisorSchmidhuber.pdf Untersuchungen zu dynamischen neuronalen Netzen]," ''Diploma thesis. Institut f. Informatik, Technische Univ. Munich. Advisor: J. Schmidhuber'', 1991.</ref><ref name="HOCH2001">{{cite book|chapter-url={{google books |plainurl=y |id=NWOcMVA64aAC}}|title=A Field Guide to Dynamical Recurrent Networks|last=Hochreiter|first=S.|display-authors=etal|date=15 January 2001|publisher=John Wiley & Sons|isbn=978-0-7803-5369-5|location=|pages=|chapter=Gradient flow in recurrent nets: the difficulty of learning long-term dependencies|editor-last2=Kremer|editor-first2=Stefan C.|editor-first1=John F.|editor-last1=Kolen}}</ref> Simpler models that use task-specific handcrafted features such as [[Gabor filter]]s and [[support vector machine]]s (SVMs) were a popular choice in the 1990s and 2000s, because of [[artificial neural network]]'s (ANN) computational cost and a lack of understanding of how the brain wires its biological networks. Both shallow and deep learning (e.g., recurrent nets) of ANNs have been explored for many years.<ref>{{Cite journal|last=Morgan|first=Nelson|last2=Bourlard |first2=Hervé |last3=Renals |first3=Steve |last4=Cohen |first4=Michael|last5=Franco |first5=Horacio |date=1993-08-01 |title=Hybrid neural network/hidden markov model systems for continuous speech recognition |journal=International Journal of Pattern Recognition and Artificial Intelligence|volume=07|issue=4|pages=899–916|doi=10.1142/s0218001493000455|issn=0218-0014}}</ref><ref name="Robinson1992">{{Cite journal|last=Robinson|first=T.|authorlink=Tony Robinson (speech recognition)|date=1992|title=A real-time recurrent error propagation network word recognition system|url=http://dl.acm.org/citation.cfm?id=1895720|journal=ICASSP|pages=617–620|via=|isbn=9780780305328|series=Icassp'92}}</ref><ref>{{Cite journal|last=Waibel|first=A.|last2=Hanazawa|first2=T.|last3=Hinton|first3=G.|last4=Shikano|first4=K.|last5=Lang|first5=K. J.|date=March 1989|title=Phoneme recognition using time-delay neural networks|journal=IEEE Transactions on Acoustics, Speech, and Signal Processing|volume=37|issue=3|pages=328–339|doi=10.1109/29.21701|issn=0096-3518|hdl=10338.dmlcz/135496|url=http://dml.cz/bitstream/handle/10338.dmlcz/135496/Kybernetika_38-2002-6_2.pdf}}</ref> These methods never outperformed non-uniform internal-handcrafting Gaussian [[mixture model]]/[[Hidden Markov model]] (GMM-HMM) technology based on generative models of speech trained discriminatively.<ref name="Baker2009">{{cite journal | last1 = Baker | first1 = J. | last2 = Deng | first2 = Li | last3 = Glass | first3 = Jim | last4 = Khudanpur | first4 = S. | last5 = Lee | first5 = C.-H. | last6 = Morgan | first6 = N. | last7 = O'Shaughnessy | first7 = D. | year = 2009 | title = Research Developments and Directions in Speech Recognition and Understanding, Part 1 | url= | journal = IEEE Signal Processing Magazine | volume = 26 | issue = 3| pages = 75–80 | doi=10.1109/msp.2009.932166| bibcode = 2009ISPM...26...75B }}</ref> Key difficulties have been analyzed, including gradient diminishing<ref name="HOCH1991" /> and weak temporal correlation structure in neural predictive models.<ref name="Bengio1991">{{Cite web|url=https://www.researchgate.net/publication/41229141|title=Artificial Neural Networks and their Application to Speech/Sequence Recognition|last=Bengio|first=Y.|date=1991|website=|publisher=McGill University Ph.D. thesis|accessdate=}}</ref><ref name="Deng1994">{{cite journal | last1 = Deng | first1 = L. | last2 = Hassanein | first2 = K. | last3 = Elmasry | first3 = M. | year = 1994 | title = Analysis of correlation structure for a neural predictive model with applications to speech recognition | url= | journal = Neural Networks | volume = 7 | issue = 2| pages = 331–339 | doi=10.1016/0893-6080(94)90027-2}}</ref> Additional difficulties were the lack of training data and limited computing power. Most [[speech recognition]] researchers moved away from neural nets to pursue generative modeling. An exception was at [[SRI International]] in the late 1990s. Funded by the US government's [[National Security Agency|NSA]] and [[DARPA]], SRI studied deep neural networks in speech and speaker recognition. The speaker recognition team led by [[Larry Heck]] reported significant success with deep neural networks in speech processing in the 1998 [[National Institute of Standards and Technology]] Speaker Recognition evaluation.<ref name="Doddington2000">{{cite journal | last1 = Doddington | first1 = G. | last2 = Przybocki | first2 = M. | last3 = Martin | first3 = A. | last4 = Reynolds | first4 = D. | year = 2000 | title = The NIST speaker recognition evaluation ± Overview, methodology, systems, results, perspective | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 225–254 | doi=10.1016/S0167-6393(99)00080-1}}</ref> The SRI deep neural network was then deployed in the Nuance Verifier, representing the first major industrial application of deep learning.<ref name="Heck2000">{{cite journal | last1 = Heck | first1 = L. | last2 = Konig | first2 = Y. | last3 = Sonmez | first3 = M. | last4 = Weintraub | first4 = M. | year = 2000 | title = Robustness to Telephone Handset Distortion in Speaker Recognition by Discriminative Feature Design | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 181–192 | doi=10.1016/s0167-6393(99)00077-1}}</ref> The principle of elevating "raw" features over hand-crafted optimization was first explored successfully in the architecture of deep autoencoder on the "raw" spectrogram or linear filter-bank features in the late 1990s,<ref name="Heck2000" /> showing its superiority over the Mel-Cepstral features that contain stages of fixed transformation from spectrograms. The raw features of speech, [[waveform]]s, later produced excellent larger-scale results.<ref>{{Cite web|url=https://www.researchgate.net/publication/266030526|title=Acoustic Modeling with Deep Neural Networks Using Raw Time Signal for LVCSR (PDF Download Available)|website=ResearchGate|accessdate=2017-06-14}}</ref> Many aspects of speech recognition were taken over by a deep learning method called [[long short-term memory]] (LSTM), a recurrent neural network published by Hochreiter and [[Jürgen Schmidhuber|Schmidhuber]] in 1997.<ref name=":0">{{Cite journal|last=Hochreiter|first=Sepp|last2=Schmidhuber|first2=Jürgen|date=1997-11-01|title=Long Short-Term Memory|journal=Neural Computation|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|issn=0899-7667|pmid=9377276|url=https://www.semanticscholar.org/paper/44d2abe2175df8153f465f6c39b68b76a0d40ab9}}</ref> LSTM RNNs avoid the vanishing gradient problem and can learn "Very Deep Learning" tasks<ref name="SCHIDHUB" /> that require memories of events that happened thousands of discrete time steps before, which is important for speech. In 2003, LSTM started to become competitive with traditional speech recognizers on certain tasks.<ref name="graves2003">{{Cite web|url=Ftp://ftp.idsia.ch/pub/juergen/bioadit2004.pdf|title=Biologically Plausible Speech Recognition with LSTM Neural Nets|last=Graves|first=Alex|last2=Eck|first2=Douglas|date=2003|website=1st Intl. Workshop on Biologically Inspired Approaches to Advanced Information Technology, Bio-ADIT 2004, Lausanne, Switzerland|pages=175–184|last3=Beringer|first3=Nicole|last4=Schmidhuber|first4=Jürgen}}</ref> Later it was combined with connectionist temporal classification (CTC)<ref name=":1">{{Cite journal|last=Graves|first=Alex|last2=Fernández|first2=Santiago|last3=Gomez|first3=Faustino|date=2006|title=Connectionist temporal classification: Labelling unsegmented sequence data with recurrent neural networks|journal=Proceedings of the International Conference on Machine Learning, ICML 2006|pages=369–376|citeseerx=10.1.1.75.6306}}</ref> in stacks of LSTM RNNs.<ref name="fernandez2007keyword">Santiago Fernandez, Alex Graves, and Jürgen Schmidhuber (2007). [https://mediatum.ub.tum.de/doc/1289941/file.pdf An application of recurrent neural networks to discriminative keyword spotting]. Proceedings of ICANN (2), pp. 220–229.</ref> In 2015, Google's speech recognition reportedly experienced a dramatic performance jump of 49% through CTC-trained LSTM, which they made available through [[Google Voice Search]].<ref name="sak2015">{{Cite web|url=http://googleresearch.blogspot.ch/2015/09/google-voice-search-faster-and-more.html|title=Google voice search: faster and more accurate|last=Sak|first=Haşim|last2=Senior|first2=Andrew|date=September 2015|website=|accessdate=|last3=Rao|first3=Kanishka|last4=Beaufays|first4=Françoise|last5=Schalkwyk|first5=Johan}}</ref> In 2006, publications by [[Geoffrey Hinton|Geoff Hinton]], [[Russ Salakhutdinov|Ruslan Salakhutdinov]], Osindero and [[Yee Whye Teh|Teh]]<ref>{{Cite journal|last=Hinton|first=Geoffrey E.|date=2007-10-01|title=Learning multiple layers of representation|url=http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(07)00217-3|journal=Trends in Cognitive Sciences|volume=11|issue=10|pages=428–434|doi=10.1016/j.tics.2007.09.004|issn=1364-6613|pmid=17921042}}</ref> <ref name=hinton06>{{Cite journal | last1 = Hinton | first1 = G. E. |authorlink1=Geoff Hinton| last2 = Osindero | first2 = S. | last3 = Teh | first3 = Y. W. | doi = 10.1162/neco.2006.18.7.1527 | title = A Fast Learning Algorithm for Deep Belief Nets | journal = [[Neural Computation (journal)|Neural Computation]]| volume = 18 | issue = 7 | pages = 1527–1554 | year = 2006 | pmid = 16764513| pmc = | url = http://www.cs.toronto.edu/~hinton/absps/fastnc.pdf}}</ref><ref name=bengio2012>{{cite arXiv |last=Bengio |first=Yoshua |author-link=Yoshua Bengio |eprint=1206.5533 |title=Practical recommendations for gradient-based training of deep architectures |class=cs.LG|year=2012 }}</ref> showed how a many-layered [[feedforward neural network]] could be effectively pre-trained one layer at a time, treating each layer in turn as an unsupervised [[restricted Boltzmann machine]], then fine-tuning it using supervised [[backpropagation]].<ref name="HINTON2007">G. E. Hinton., "[http://www.csri.utoronto.ca/~hinton/absps/ticsdraft.pdf Learning multiple layers of representation]," ''Trends in Cognitive Sciences'', 11, pp. 428–434, 2007.</ref> The papers referred to ''learning'' for ''deep belief nets.'' Deep learning is part of state-of-the-art systems in various disciplines, particularly computer vision and [[automatic speech recognition]] (ASR). Results on commonly used evaluation sets such as [[TIMIT]] (ASR) and [[MNIST database|MNIST]] ([[image classification]]), as well as a range of large-vocabulary speech recognition tasks have steadily improved.<ref name="HintonDengYu2012" /><ref>{{cite journal|url=https://www.microsoft.com/en-us/research/publication/new-types-of-deep-neural-network-learning-for-speech-recognition-and-related-applications-an-overview/|title=New types of deep neural network learning for speech recognition and related applications: An overview|journal=Microsoft Research|first1=Li|last1=Deng|first2=Geoffrey|last2=Hinton|first3=Brian|last3=Kingsbury|date=1 May 2013|via=research.microsoft.com|citeseerx=10.1.1.368.1123}}</ref><ref>{{Cite book |doi=10.1109/icassp.2013.6639345|isbn=978-1-4799-0356-6|chapter=Recent advances in deep learning for speech research at Microsoft|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8604–8608|year=2013|last1=Deng|first1=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Michael|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|last10=Williams|first10=Jason|last11=Gong|first11=Yifan|last12=Acero|first12=Alex}}</ref> [[Convolutional neural network]]s (CNNs) were superseded for ASR by CTC<ref name=":1" /> for LSTM.<ref name=":0" /><ref name="sak2015" /><ref name="sak2014">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|title=Long Short-Term Memory recurrent neural network architectures for large scale acoustic modeling|last=Sak|first=Hasim|last2=Senior|first2=Andrew|date=2014|website=|accessdate=|last3=Beaufays|first3=Francoise|archive-url=https://web.archive.org/web/20180424203806/https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|archive-date=2018-04-24|url-status=dead}}</ref><ref name="liwu2015">{{cite arxiv |eprint=1410.4281|last1=Li|first1=Xiangang|title=Constructing Long Short-Term Memory based Deep Recurrent Neural Networks for Large Vocabulary Speech Recognition|last2=Wu|first2=Xihong|class=cs.CL|year=2014}}</ref><ref name="zen2015">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=Unidirectional Long Short-Term Memory Recurrent Neural Network with Recurrent Output Layer for Low-Latency Speech Synthesis|last=Zen|first=Heiga|last2=Sak|first2=Hasim|date=2015|website=Google.com|publisher=ICASSP|pages=4470–4474|accessdate=}}</ref><ref name="CNNspeech2013">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=A deep convolutional neural network using heterogeneous pooling for trading acoustic invariance with phonetic confusion|last=Deng|first=L.|last2=Abdel-Hamid|first2=O.|date=2013|website=Google.com|publisher=ICASSP|accessdate=|last3=Yu|first3=D.}}</ref><ref name=":2">{{Cite book |doi=10.1109/icassp.2013.6639347|isbn=978-1-4799-0356-6|chapter=Deep convolutional neural networks for LVCSR|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8614–8618|year=2013|last1=Sainath|first1=Tara N.|last2=Mohamed|first2=Abdel-Rahman|last3=Kingsbury|first3=Brian|last4=Ramabhadran|first4=Bhuvana}}</ref> but are more successful in computer vision. The impact of deep learning in industry began in the early 2000s, when CNNs already processed an estimated 10% to 20% of all the checks written in the US, according to Yann LeCun.<ref name="lecun2016slides">[[Yann LeCun]] (2016). Slides on Deep Learning [https://indico.cern.ch/event/510372/ Online]</ref> Industrial applications of deep learning to large-scale speech recognition started around 2010. The 2009 NIPS Workshop on Deep Learning for Speech Recognition<ref name="NIPS2009" /> was motivated by the limitations of deep generative models of speech, and the possibility that given more capable hardware and large-scale data sets that deep neural nets (DNN) might become practical. It was believed that pre-training DNNs using generative models of deep belief nets (DBN) would overcome the main difficulties of neural nets.<ref name="HintonKeynoteICASSP2013" /> However, it was discovered that replacing pre-training with large amounts of training data for straightforward backpropagation when using DNNs with large, context-dependent output layers produced error rates dramatically lower than then-state-of-the-art Gaussian mixture model (GMM)/Hidden Markov Model (HMM) and also than more-advanced generative model-based systems.<ref name="HintonDengYu2012">{{cite journal | last1 = Hinton | first1 = G. | last2 = Deng | first2 = L. | last3 = Yu | first3 = D. | last4 = Dahl | first4 = G. | last5 = Mohamed | first5 = A. | last6 = Jaitly | first6 = N. | last7 = Senior | first7 = A. | last8 = Vanhoucke | first8 = V. | last9 = Nguyen | first9 = P. | last10 = Sainath | first10 = T. | last11 = Kingsbury | first11 = B. | year = 2012 | title = Deep Neural Networks for Acoustic Modeling in Speech Recognition: The Shared Views of Four Research Groups| url= | journal = IEEE Signal Processing Magazine | volume = 29 | issue = 6| pages = 82–97 | doi=10.1109/msp.2012.2205597}}</ref><ref name="patent2011">D. Yu, L. Deng, G. Li, and F. Seide (2011). "Discriminative pretraining of deep neural networks," U.S. Patent Filing.</ref> The nature of the recognition errors produced by the two types of systems was characteristically different,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009">NIPS Workshop: Deep Learning for Speech Recognition and Related Applications, Whistler, BC, Canada, Dec. 2009 (Organizers: Li Deng, Geoff Hinton, D. Yu).</ref> offering technical insights into how to integrate deep learning into the existing highly efficient, run-time speech decoding system deployed by all major speech recognition systems.<ref name="BOOK2014" /><ref name="ReferenceA">{{cite book|last2=Deng|first2=L.|date=2014|title=Automatic Speech Recognition: A Deep Learning Approach (Publisher: Springer)|url={{google books |plainurl=y |id=rUBTBQAAQBAJ}}|pages=|isbn=978-1-4471-5779-3|via=|last1=Yu|first1=D.}}</ref><ref>{{cite web|title=Deng receives prestigious IEEE Technical Achievement Award - Microsoft Research|url=https://www.microsoft.com/en-us/research/blog/deng-receives-prestigious-ieee-technical-achievement-award/|website=Microsoft Research|date=3 December 2015}}</ref> Analysis around 2009-2010, contrasted the GMM (and other generative speech models) vs. DNN models, stimulated early industrial investment in deep learning for speech recognition,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009" /> eventually leading to pervasive and dominant use in that industry. That analysis was done with comparable performance (less than 1.5% in error rate) between discriminative DNNs and generative models.<ref name="HintonDengYu2012" /><ref name="ReferenceICASSP2013">{{cite journal|last2=Hinton|first2=G.|last3=Kingsbury|first3=B.|date=2013|title=New types of deep neural network learning for speech recognition and related applications: An overview (ICASSP)|url=https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/ICASSP-2013-DengHintonKingsbury-revised.pdf|journal=|pages=|via=|last1=Deng|first1=L.}}</ref><ref name="HintonKeynoteICASSP2013">Keynote talk: Recent Developments in Deep Neural Networks. ICASSP, 2013 (by Geoff Hinton).</ref><ref name="interspeech2014Keynote">{{Cite web|url=https://www.superlectures.com/interspeech2014/downloadFile?id=6&type=slides&filename=achievements-and-challenges-of-deep-learning-from-speech-analysis-and-recognition-to-language-and-multimodal-processing|title=Keynote talk: 'Achievements and Challenges of Deep Learning - From Speech Analysis and Recognition To Language and Multimodal Processing'|last=Li|first=Deng|date=September 2014|website=Interspeech|accessdate=}}</ref> In 2010, researchers extended deep learning from TIMIT to large vocabulary speech recognition, by adopting large output layers of the DNN based on context-dependent HMM states constructed by [[decision tree]]s.<ref name="Roles2010">{{cite journal|last1=Yu|first1=D.|last2=Deng|first2=L.|date=2010|title=Roles of Pre-Training and Fine-Tuning in Context-Dependent DBN-HMMs for Real-World Speech Recognition|url=https://www.microsoft.com/en-us/research/publication/roles-of-pre-training-and-fine-tuning-in-context-dependent-dbn-hmms-for-real-world-speech-recognition/|journal=NIPS Workshop on Deep Learning and Unsupervised Feature Learning|pages=|via=}}</ref><ref>{{Cite journal|last=Seide|first=F.|last2=Li|first2=G.|last3=Yu|first3=D.|date=2011|title=Conversational speech transcription using context-dependent deep neural networks|url=https://www.microsoft.com/en-us/research/publication/conversational-speech-transcription-using-context-dependent-deep-neural-networks|journal=Interspeech|pages=|via=}}</ref><ref>{{Cite journal|last=Deng|first=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Mike|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|date=2013-05-01|title=Recent Advances in Deep Learning for Speech Research at Microsoft|url=https://www.microsoft.com/en-us/research/publication/recent-advances-in-deep-learning-for-speech-research-at-microsoft/|journal=Microsoft Research}}</ref><ref name="ReferenceA" /> Advances in hardware have enabled renewed interest in deep learning. In 2009, [[Nvidia]] was involved in what was called the “big bang” of deep learning, “as deep-learning neural networks were trained with Nvidia [[graphics processing unit]]s (GPUs).”<ref>{{cite web|url=https://venturebeat.com/2016/04/05/nvidia-ceo-bets-big-on-deep-learning-and-vr/|title=Nvidia CEO bets big on deep learning and VR|date=April 5, 2016|publisher=[[Venture Beat]]}}</ref> That year, [[Google Brain]] used Nvidia GPUs to create capable DNNs. While there, [[Andrew Ng]] determined that GPUs could increase the speed of deep-learning systems by about 100 times.<ref>{{cite news|url=https://www.economist.com/news/special-report/21700756-artificial-intelligence-boom-based-old-idea-modern-twist-not|title=From not working to neural networking|newspaper=[[The Economist]]}}</ref> In particular, GPUs are well-suited for the matrix/vector computations involved in machine learning.<ref name="jung2004">{{cite journal | last1 = Oh | first1 = K.-S. | last2 = Jung | first2 = K. | year = 2004 | title = GPU implementation of neural networks | url= | journal = Pattern Recognition | volume = 37 | issue = 6| pages = 1311–1314 | doi=10.1016/j.patcog.2004.01.013}}</ref><ref>"[https://www.academia.edu/40135801 A Survey of Techniques for Optimizing Deep Learning on GPUs]", S. Mittal and S. Vaishay, Journal of Systems Architecture, 2019</ref><ref name="chellapilla2006">Chellapilla, K., Puri, S., and Simard, P. (2006). High performance convolutional neural networks for document processing. International Workshop on Frontiers in Handwriting Recognition.</ref> GPUs speed up training algorithms by orders of magnitude, reducing running times from weeks to days.<ref name=":3">{{Cite journal|last=Cireşan|first=Dan Claudiu|last2=Meier|first2=Ueli|last3=Gambardella|first3=Luca Maria|last4=Schmidhuber|first4=Jürgen|date=2010-09-21|title=Deep, Big, Simple Neural Nets for Handwritten Digit Recognition|journal=Neural Computation|volume=22|issue=12|pages=3207–3220|doi=10.1162/neco_a_00052|pmid=20858131|issn=0899-7667|arxiv=1003.0358}}</ref><ref>{{Cite journal|last=Raina|first=Rajat|last2=Madhavan|first2=Anand|last3=Ng|first3=Andrew Y.|date=2009|title=Large-scale Deep Unsupervised Learning Using Graphics Processors|journal=Proceedings of the 26th Annual International Conference on Machine Learning|series=ICML '09|location=New York, NY, USA|publisher=ACM|pages=873–880|doi=10.1145/1553374.1553486|isbn=9781605585161|citeseerx=10.1.1.154.372|url=https://www.semanticscholar.org/paper/e337c5e4c23999c36f64bcb33ebe6b284e1bcbf1}}</ref> Further, specialized hardware and algorithm optimizations can be used for efficient processing of deep learning models.<ref name="sze2017">{{cite arXiv |title= Efficient Processing of Deep Neural Networks: A Tutorial and Survey |last1=Sze |first1=Vivienne |last2=Chen |first2=Yu-Hsin |last3=Yang |first3=Tien-Ju |last4=Emer |first4=Joel |eprint=1703.09039 |year=2017 |class=cs.CV }}</ref> === Deep learning revolution === [[File:AI-ML-DL.png|thumb|How deep learning is a subset of machine learning and how machine learning is a subset of artificial intelligence (AI).]] In 2012, a team led by George E. Dahl won the "Merck Molecular Activity Challenge" using multi-task deep neural networks to predict the [[biomolecular target]] of one drug.<ref name="MERCK2012">{{cite web|url=https://www.kaggle.com/c/MerckActivity/details/winners|title=Announcement of the winners of the Merck Molecular Activity Challenge}}</ref><ref name=":5">{{Cite web|url=http://www.datascienceassn.org/content/multi-task-neural-networks-qsar-predictions|title=Multi-task Neural Networks for QSAR Predictions {{!}} Data Science Association|website=www.datascienceassn.org|accessdate=2017-06-14}}</ref> In 2014, Hochreiter's group used deep learning to detect off-target and toxic effects of environmental chemicals in nutrients, household products and drugs and won the "Tox21 Data Challenge" of [[NIH]], [[FDA]] and [[National Center for Advancing Translational Sciences|NCATS]].<ref name="TOX21">"Toxicology in the 21st century Data Challenge"</ref><ref name="TOX21Data">{{cite web|url=https://tripod.nih.gov/tox21/challenge/leaderboard.jsp|title=NCATS Announces Tox21 Data Challenge Winners}}</ref><ref name=":11">{{cite web|url=http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|title=Archived copy|archiveurl=https://web.archive.org/web/20150228225709/http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|archivedate=2015-02-28|url-status=dead|accessdate=2015-03-05}}</ref> Significant additional impacts in image or object recognition were felt from 2011 to 2012. Although CNNs trained by backpropagation had been around for decades, and GPU implementations of NNs for years, including CNNs, fast implementations of CNNs with max-pooling on GPUs in the style of Ciresan and colleagues were needed to progress on computer vision.<ref name="jung2004" /><ref name="chellapilla2006" /><ref name="LECUN1989" /><ref name=":6">{{Cite journal|last=Ciresan|first=D. C.|last2=Meier|first2=U.|last3=Masci|first3=J.|last4=Gambardella|first4=L. M.|last5=Schmidhuber|first5=J.|date=2011|title=Flexible, High Performance Convolutional Neural Networks for Image Classification|url=http://ijcai.org/papers11/Papers/IJCAI11-210.pdf|journal=International Joint Conference on Artificial Intelligence|pages=|doi=10.5591/978-1-57735-516-8/ijcai11-210|via=}}</ref><ref name="SCHIDHUB" /> In 2011, this approach achieved for the first time superhuman performance in a visual pattern recognition contest. Also in 2011, it won the ICDAR Chinese handwriting contest, and in May 2012, it won the ISBI image segmentation contest.<ref name=":8">{{Cite book|url=http://papers.nips.cc/paper/4741-deep-neural-networks-segment-neuronal-membranes-in-electron-microscopy-images.pdf|title=Advances in Neural Information Processing Systems 25|last=Ciresan|first=Dan|last2=Giusti|first2=Alessandro|last3=Gambardella|first3=Luca M.|last4=Schmidhuber|first4=Juergen|date=2012|publisher=Curran Associates, Inc.|editor-last=Pereira|editor-first=F.|pages=2843–2851|editor-last2=Burges|editor-first2=C. J. C.|editor-last3=Bottou|editor-first3=L.|editor-last4=Weinberger|editor-first4=K. Q.}}</ref> Until 2011, CNNs did not play a major role at computer vision conferences, but in June 2012, a paper by Ciresan et al. at the leading conference CVPR<ref name=":9" /> showed how max-pooling CNNs on GPU can dramatically improve many vision benchmark records. In October 2012, a similar system by Krizhevsky et al.<ref name="krizhevsky2012" /> won the large-scale [[ImageNet competition]] by a significant margin over shallow machine learning methods. In November 2012, Ciresan et al.'s system also won the ICPR contest on analysis of large medical images for cancer detection, and in the following year also the MICCAI Grand Challenge on the same topic.<ref name="ciresan2013miccai">{{Cite journal|last=Ciresan|first=D.|last2=Giusti|first2=A.|last3=Gambardella|first3=L.M.|last4=Schmidhuber|first4=J.|date=2013|title=Mitosis Detection in Breast Cancer Histology Images using Deep Neural Networks|journal=Proceedings MICCAI|volume=7908|issue=Pt 2|pages=411–418|doi=10.1007/978-3-642-40763-5_51|pmid=24579167|series=Lecture Notes in Computer Science|isbn=978-3-642-38708-1}}</ref> In 2013 and 2014, the error rate on the ImageNet task using deep learning was further reduced, following a similar trend in large-scale speech recognition. The [[Stephen Wolfram|Wolfram]] Image Identification project publicized these improvements.<ref>{{Cite web|url=https://www.imageidentify.com/|title=The Wolfram Language Image Identification Project|website=www.imageidentify.com|accessdate=2017-03-22}}</ref> Image classification was then extended to the more challenging task of [[Automatic image annotation|generating descriptions]] (captions) for images, often as a combination of CNNs and LSTMs.<ref name="1411.4555">{{cite arxiv |eprint=1411.4555|last1=Vinyals|first1=Oriol|title=Show and Tell: A Neural Image Caption Generator|last2=Toshev|first2=Alexander|last3=Bengio|first3=Samy|last4=Erhan|first4=Dumitru|class=cs.CV|year=2014}}.</ref><ref name="1411.4952">{{cite arxiv |eprint=1411.4952|last1=Fang|first1=Hao|title=From Captions to Visual Concepts and Back|last2=Gupta|first2=Saurabh|last3=Iandola|first3=Forrest|last4=Srivastava|first4=Rupesh|last5=Deng|first5=Li|last6=Dollár|first6=Piotr|last7=Gao|first7=Jianfeng|last8=He|first8=Xiaodong|last9=Mitchell|first9=Margaret|last10=Platt|first10=John C|last11=Lawrence Zitnick|first11=C|last12=Zweig|first12=Geoffrey|class=cs.CV|year=2014}}.</ref><ref name="1411.2539">{{cite arxiv |eprint=1411.2539|last1=Kiros|first1=Ryan|title=Unifying Visual-Semantic Embeddings with Multimodal Neural Language Models|last2=Salakhutdinov|first2=Ruslan|last3=Zemel|first3=Richard S|class=cs.LG|year=2014}}.</ref><ref>{{Cite journal|last=Zhong|first=Sheng-hua|last2=Liu|first2=Yan|last3=Liu|first3=Yang|date=2011|title=Bilinear Deep Learning for Image Classification|journal=Proceedings of the 19th ACM International Conference on Multimedia|series=MM '11|location=New York, NY, USA|publisher=ACM|pages=343–352|doi=10.1145/2072298.2072344|isbn=9781450306164|url=https://www.semanticscholar.org/paper/e1bbfb2c7ef74445b4fad9199b727464129df582}}</ref> Some researchers assess that the October 2012 ImageNet victory anchored the start of a "deep learning revolution" that has transformed the AI industry.<ref>{{cite news|title=Why Deep Learning Is Suddenly Changing Your Life|url=http://fortune.com/ai-artificial-intelligence-deep-machine-learning/|accessdate=13 April 2018|work=Fortune|date=2016}}</ref> In March 2019, [[Yoshua Bengio]], [[Geoffrey Hinton]] and [[Yann LeCun]] were awarded the [[Turing Award]] for conceptual and engineering breakthroughs that have made deep neural networks a critical component of computing. == Neural networks == === Artificial neural networks === {{Main|Artificial neural network}} '''Artificial neural networks''' ('''ANNs''') or '''[[Connectionism|connectionist]] systems''' are computing systems inspired by the [[biological neural network]]s that constitute animal brains. Such systems learn (progressively improve their ability) to do tasks by considering examples, generally without task-specific programming. For example, in image recognition, they might learn to identify images that contain cats by analyzing example images that have been manually [[Labeled data|labeled]] as "cat" or "no cat" and using the analytic results to identify cats in other images. They have found most use in applications difficult to express with a traditional computer algorithm using [[rule-based programming]]. An ANN is based on a collection of connected units called [[artificial neuron]]s, (analogous to biological neurons in a [[Brain|biological brain]]). Each connection ([[synapse]]) between neurons can transmit a signal to another neuron. The receiving (postsynaptic) neuron can process the signal(s) and then signal downstream neurons connected to it. Neurons may have state, generally represented by [[real numbers]], typically between 0 and 1. Neurons and synapses may also have a weight that varies as learning proceeds, which can increase or decrease the strength of the signal that it sends downstream. Typically, neurons are organized in layers. Different layers may perform different kinds of transformations on their inputs. Signals travel from the first (input), to the last (output) layer, possibly after traversing the layers multiple times. The original goal of the neural network approach was to solve problems in the same way that a human brain would. Over time, attention focused on matching specific mental abilities, leading to deviations from biology such as backpropagation, or passing information in the reverse direction and adjusting the network to reflect that information. Neural networks have been used on a variety of tasks, including computer vision, [[speech recognition]], [[machine translation]], [[social network]] filtering, [[general game playing|playing board and video games]] and medical diagnosis. As of 2017, neural networks typically have a few thousand to a few million units and millions of connections. Despite this number being several order of magnitude less than the number of neurons on a human brain, these networks can perform many tasks at a level beyond that of humans (e.g., recognizing faces, playing "Go"<ref>{{Cite journal|last=Silver|first=David|last2=Huang|first2=Aja|last3=Maddison|first3=Chris J.|last4=Guez|first4=Arthur|last5=Sifre|first5=Laurent|last6=Driessche|first6=George van den|last7=Schrittwieser|first7=Julian|last8=Antonoglou|first8=Ioannis|last9=Panneershelvam|first9=Veda|date=January 2016|title=Mastering the game of Go with deep neural networks and tree search|journal=Nature|volume=529|issue=7587|pages=484–489|doi=10.1038/nature16961|issn=1476-4687|pmid=26819042|bibcode=2016Natur.529..484S|url=https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}</ref> ). === Deep neural networks === {{technical|section|date=July 2016}} A deep neural network (DNN) is an [[artificial neural network]] (ANN) with multiple layers between the input and output layers.<ref name="BENGIODEEP" /><ref name="SCHIDHUB" /> The DNN finds the correct mathematical manipulation to turn the input into the output, whether it be a [[linear relationship]] or a non-linear relationship. The network moves through the layers calculating the probability of each output. For example, a DNN that is trained to recognize dog breeds will go over the given image and calculate the probability that the dog in the image is a certain breed. The user can review the results and select which probabilities the network should display (above a certain threshold, etc.) and return the proposed label. Each mathematical manipulation as such is considered a layer, and complex DNN have many layers, hence the name "deep" networks. DNNs can model complex non-linear relationships. DNN architectures generate compositional models where the object is expressed as a layered composition of [[Primitive data type|primitives]].<ref>{{Cite journal|last=Szegedy|first=Christian|last2=Toshev|first2=Alexander|last3=Erhan|first3=Dumitru|date=2013|title=Deep neural networks for object detection|url=https://papers.nips.cc/paper/5207-deep-neural-networks-for-object-detection|journal=Advances in Neural Information Processing Systems|pages=2553–2561|via=}}</ref> The extra layers enable composition of features from lower layers, potentially modeling complex data with fewer units than a similarly performing shallow network.<ref name="BENGIODEEP" /> Deep architectures include many variants of a few basic approaches. Each architecture has found success in specific domains. It is not always possible to compare the performance of multiple architectures, unless they have been evaluated on the same data sets. DNNs are typically feedforward networks in which data flows from the input layer to the output layer without looping back. At first, the DNN creates a map of virtual neurons and assigns random numerical values, or "weights", to connections between them. The weights and inputs are multiplied and return an output between 0 and 1. If the network did not accurately recognize a particular pattern, an algorithm would adjust the weights.<ref>{{Cite news|url=https://www.technologyreview.com/s/513696/deep-learning/|title=Is Artificial Intelligence Finally Coming into Its Own?|last=Hof|first=Robert D.|work=MIT Technology Review|access-date=2018-07-10}}</ref> That way the algorithm can make certain parameters more influential, until it determines the correct mathematical manipulation to fully process the data. [[Recurrent neural networks]] (RNNs), in which data can flow in any direction, are used for applications such as [[language model]]ing.<ref name="gers2001">{{cite journal|last1=Gers|first1=Felix A.|last2=Schmidhuber|first2=Jürgen|year=2001|title=LSTM Recurrent Networks Learn Simple Context Free and Context Sensitive Languages|url=http://elartu.tntu.edu.ua/handle/lib/30719|journal= IEEE Transactions on Neural Networks|volume=12|issue=6|pages=1333–1340|doi=10.1109/72.963769|pmid=18249962}}</ref><ref name="NIPS2014"/><ref name="vinyals2016">{{cite arxiv |eprint=1602.02410|last1=Jozefowicz|first1=Rafal|title=Exploring the Limits of Language Modeling|last2=Vinyals|first2=Oriol|last3=Schuster|first3=Mike|last4=Shazeer|first4=Noam|last5=Wu|first5=Yonghui|class=cs.CL|year=2016}}</ref><ref name="gillick2015">{{cite arxiv |eprint=1512.00103|last1=Gillick|first1=Dan|title=Multilingual Language Processing from Bytes|last2=Brunk|first2=Cliff|last3=Vinyals|first3=Oriol|last4=Subramanya|first4=Amarnag|class=cs.CL|year=2015}}</ref><ref name="MIKO2010">{{Cite journal|last=Mikolov|first=T.|display-authors=etal|date=2010|title=Recurrent neural network based language model|url=http://www.fit.vutbr.cz/research/groups/speech/servite/2010/rnnlm_mikolov.pdf|journal=Interspeech|pages=|via=}}</ref> Long short-term memory is particularly effective for this use.<ref name=":0" /><ref name=":10">{{Cite web|url=https://www.researchgate.net/publication/220320057|title=Learning Precise Timing with LSTM Recurrent Networks (PDF Download Available)|website=ResearchGate|accessdate=2017-06-13}}</ref> [[Convolutional neural network|Convolutional deep neural networks (CNNs)]] are used in computer vision.<ref name="LECUN86">{{cite journal |last1=LeCun |first1=Y. |display-authors=etal |year= 1998|title=Gradient-based learning applied to document recognition |url= |journal=Proceedings of the IEEE |volume=86 |issue=11 |pages=2278–2324 |doi=10.1109/5.726791}}</ref> CNNs also have been applied to [[acoustic model]]ing for automatic speech recognition (ASR).<ref name=":2" /> ==== Challenges ==== As with ANNs, many issues can arise with naively trained DNNs. Two common issues are [[overfitting]] and computation time. DNNs are prone to overfitting because of the added layers of abstraction, which allow them to model rare dependencies in the training data. [[Regularization (mathematics)|Regularization]] methods such as Ivakhnenko's unit pruning<ref name="ivak1971"/> or [[weight decay]] (<math> \ell_2 </math>-regularization) or [[sparse matrix|sparsity]] (<math> \ell_1 </math>-regularization) can be applied during training to combat overfitting.<ref>{{Cite book |doi=10.1109/icassp.2013.6639349|isbn=978-1-4799-0356-6|arxiv=1212.0901|citeseerx=10.1.1.752.9151|chapter=Advances in optimizing recurrent networks|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8624–8628|year=2013|last1=Bengio|first1=Yoshua|last2=Boulanger-Lewandowski|first2=Nicolas|last3=Pascanu|first3=Razvan}}</ref> Alternatively dropout regularization randomly omits units from the hidden layers during training. This helps to exclude rare dependencies.<ref name="DAHL2013">{{Cite journal|last=Dahl|first=G.|display-authors=etal|date=2013|title=Improving DNNs for LVCSR using rectified linear units and dropout|url=http://www.cs.toronto.edu/~gdahl/papers/reluDropoutBN_icassp2013.pdf|journal=ICASSP|pages=|via=}}</ref> Finally, data can be augmented via methods such as cropping and rotating such that smaller training sets can be increased in size to reduce the chances of overfitting.<ref>{{Cite web|url=https://www.coursera.org/learn/convolutional-neural-networks/lecture/AYzbX/data-augmentation|title=Data Augmentation - deeplearning.ai {{!}} Coursera|website=Coursera|accessdate=2017-11-30}}</ref> DNNs must consider many training parameters, such as the size (number of layers and number of units per layer), the [[learning rate]], and initial weights. [[Hyperparameter optimization#Grid search|Sweeping through the parameter space]] for optimal parameters may not be feasible due to the cost in time and computational resources. Various tricks, such as batching (computing the gradient on several training examples at once rather than individual examples)<ref name="RBMTRAIN">{{Cite journal|last=Hinton|first=G. E.|date=2010|title=A Practical Guide to Training Restricted Boltzmann Machines|url=https://www.researchgate.net/publication/221166159|journal=Tech. Rep. UTML TR 2010-003|pages=|via=}}</ref> speed up computation. Large processing capabilities of many-core architectures (such as GPUs or the Intel Xeon Phi) have produced significant speedups in training, because of the suitability of such processing architectures for the matrix and vector computations.<ref>{{cite book|last1=You|first1=Yang|title=Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis on - SC '17|pages=1–12|last2=Buluç|first2=Aydın|last3=Demmel|first3=James|chapter=Scaling deep learning on GPU and knights landing clusters|chapter-url=https://dl.acm.org/citation.cfm?doid=3126908.3126912|publisher=SC '17, ACM|date=November 2017|accessdate=5 March 2018|doi=10.1145/3126908.3126912|isbn=9781450351140|url=http://www.escholarship.org/uc/item/6ch40821}}</ref><ref>{{cite journal|last1=Viebke|first1=André|last2=Memeti|first2=Suejb|last3=Pllana|first3=Sabri|last4=Abraham|first4=Ajith|title=CHAOS: a parallelization scheme for training convolutional neural networks on Intel Xeon Phi|journal=The Journal of Supercomputing|volume=75|pages=197–227|doi=10.1007/s11227-017-1994-x|accessdate=|arxiv=1702.07908|bibcode=2017arXiv170207908V|url=https://www.semanticscholar.org/paper/aa8a4d2de94cc0a8ccff21f651c005613e8ec0e8|year=2019}}</ref> Alternatively, engineers may look for other types of neural networks with more straightforward and convergent training algorithms. CMAC ([[cerebellar model articulation controller]]) is one such kind of neural network. It doesn't require learning rates or randomized initial weights for CMAC. The training process can be guaranteed to converge in one step with a new batch of data, and the computational complexity of the training algorithm is linear with respect to the number of neurons involved.<ref name=Qin1>Ting Qin, et al. "A learning algorithm of CMAC based on RLS." Neural Processing Letters 19.1 (2004): 49-61.</ref><ref name=Qin2>Ting Qin, et al. "[http://www-control.eng.cam.ac.uk/Homepage/papers/cued_control_997.pdf Continuous CMAC-QRLS and its systolic array]." Neural Processing Letters 22.1 (2005): 1-16.</ref> == Applications == === Automatic speech recognition === {{Main|Speech recognition}} Large-scale automatic speech recognition is the first and most convincing successful case of deep learning. LSTM RNNs can learn "Very Deep Learning" tasks<ref name="SCHIDHUB"/> that involve multi-second intervals containing speech events separated by thousands of discrete time steps, where one time step corresponds to about 10 ms. LSTM with forget gates<ref name=":10" /> is competitive with traditional speech recognizers on certain tasks.<ref name="graves2003"/> The initial success in speech recognition was based on small-scale recognition tasks based on TIMIT. The data set contains 630 speakers from eight major [[dialect]]s of [[American English]], where each speaker reads 10 sentences.<ref name="LDCTIMIT">''TIMIT Acoustic-Phonetic Continuous Speech Corpus'' Linguistic Data Consortium, Philadelphia.</ref> Its small size lets many configurations be tried. More importantly, the TIMIT task concerns phone-sequence recognition, which, unlike word-sequence recognition, allows weak phone [[bigram]] language models. This lets the strength of the acoustic modeling aspects of speech recognition be more easily analyzed. The error rates listed below, including these early results and measured as percent phone error rates (PER), have been summarized since 1991. {| class="wikitable" |- ! Method !! Percent phone<br>error rate (PER) (%) |- | Randomly Initialized RNN<ref>{{cite journal |last1=Robinson |first1=Tony |authorlink=Tony Robinson (speech recognition)|title=Several Improvements to a Recurrent Error Propagation Network Phone Recognition System |journal=Cambridge University Engineering Department Technical Report |date=30 September 1991 |volume=CUED/F-INFENG/TR82 |doi=10.13140/RG.2.2.15418.90567 }}</ref>|| 26.1 |- | Bayesian Triphone GMM-HMM || 25.6 |- | Hidden Trajectory (Generative) Model|| 24.8 |- | Monophone Randomly Initialized DNN|| 23.4 |- | Monophone DBN-DNN|| 22.4 |- | Triphone GMM-HMM with BMMI Training|| 21.7 |- | Monophone DBN-DNN on fbank || 20.7 |- | Convolutional DNN<ref name="CNN-2014">{{cite journal|last1=Abdel-Hamid|first1=O.|title=Convolutional Neural Networks for Speech Recognition|journal=IEEE/ACM Transactions on Audio, Speech, and Language Processing|date=2014|volume=22|issue=10|pages=1533–1545|doi=10.1109/taslp.2014.2339736|display-authors=etal|url=https://zenodo.org/record/891433}}</ref>|| 20.0 |- | Convolutional DNN w. Heterogeneous Pooling|| 18.7 |- | Ensemble DNN/CNN/RNN<ref name="EnsembleDL">{{cite journal|last2=Platt|first2=J.|date=2014|title=Ensemble Deep Learning for Speech Recognition|url=https://pdfs.semanticscholar.org/8201/55ecb57325503183253b8796de5f4535eb16.pdf|journal=Proc. Interspeech|pages=|via=|last1=Deng|first1=L.}}</ref>|| 18.3 |- | Bidirectional LSTM|| 17.9 |- | Hierarchical Convolutional Deep Maxout Network<ref name="HCDMM">{{cite journal|last1=Tóth|first1=Laszló|date=2015|title=Phone Recognition with Hierarchical Convolutional Deep Maxout Networks|journal=EURASIP Journal on Audio, Speech, and Music Processing|volume=2015|doi=10.1186/s13636-015-0068-3|url=http://publicatio.bibl.u-szeged.hu/5976/1/EURASIP2015.pdf}}</ref> || 16.5 |} The debut of DNNs for speaker recognition in the late 1990s and speech recognition around 2009-2011 and of LSTM around 2003-2007, accelerated progress in eight major areas:<ref name="BOOK2014" /><ref name="interspeech2014Keynote" /><ref name="ReferenceA" /> * Scale-up/out and accelerated DNN training and decoding * Sequence discriminative training * Feature processing by deep models with solid understanding of the underlying mechanisms * Adaptation of DNNs and related deep models * [[Multi-task learning|Multi-task]] and [[Inductive transfer|transfer learning]] by DNNs and related deep models * CNNs and how to design them to best exploit [[domain knowledge]] of speech * RNN and its rich LSTM variants * Other types of deep models including tensor-based models and integrated deep generative/discriminative models. All major commercial speech recognition systems (e.g., Microsoft [[Cortana (software)|Cortana]], [[Xbox]], [[Skype Translator]], [[Amazon Alexa]], [[Google Now]], [[Siri|Apple Siri]], [[Baidu]] and [[IFlytek|iFlyTek]] voice search, and a range of [[Nuance Communications|Nuance]] speech products, etc.) are based on deep learning.<ref name=BOOK2014 /><ref>{{Cite journal|url=https://www.wired.com/2014/12/skype-used-ai-build-amazing-new-language-translator/|title=How Skype Used AI to Build Its Amazing New Language Translator {{!}} WIRED|journal=Wired|accessdate=2017-06-14|date=2014-12-17|last1=McMillan|first1=Robert}}</ref><ref name="Baidu">{{cite arxiv |eprint=1412.5567|last1=Hannun|first1=Awni|title=Deep Speech: Scaling up end-to-end speech recognition|last2=Case|first2=Carl|last3=Casper|first3=Jared|last4=Catanzaro|first4=Bryan|last5=Diamos|first5=Greg|last6=Elsen|first6=Erich|last7=Prenger|first7=Ryan|last8=Satheesh|first8=Sanjeev|last9=Sengupta|first9=Shubho|last10=Coates|first10=Adam|last11=Ng|first11=Andrew Y|class=cs.CL|year=2014}}</ref><ref>{{Cite web|url=http://research.microsoft.com/en-US/people/deng/ieee-icassp-plenary-2016-mar24-lideng-posted.pdf|title=Plenary presentation at ICASSP-2016|date=|website=|accessdate=}}</ref> === Image recognition === {{Main|Computer vision}} A common evaluation set for image classification is the MNIST database data set. MNIST is composed of handwritten digits and includes 60,000 training examples and 10,000 test examples. As with TIMIT, its small size lets users test multiple configurations. A comprehensive list of results on this set is available.<ref name="YANNMNIST">{{cite web|url=http://yann.lecun.com/exdb/mnist/.|title=MNIST handwritten digit database, Yann LeCun, Corinna Cortes and Chris Burges|website=yann.lecun.com}}</ref> Deep learning-based image recognition has become "superhuman", producing more accurate results than human contestants. This first occurred in 2011.<ref name=":7">{{Cite journal|last=Cireşan|first=Dan|last2=Meier|first2=Ueli|last3=Masci|first3=Jonathan|last4=Schmidhuber|first4=Jürgen|date=August 2012|title=Multi-column deep neural network for traffic sign classification|journal=Neural Networks|series=Selected Papers from IJCNN 2011|volume=32|pages=333–338|doi=10.1016/j.neunet.2012.02.023|pmid=22386783|citeseerx=10.1.1.226.8219}}</ref> Deep learning-trained vehicles now interpret 360° camera views.<ref>[http://www.technologyreview.com/news/533936/nvidia-demos-a-car-computer-trained-with-deep-learning/ Nvidia Demos a Car Computer Trained with "Deep Learning"] (2015-01-06), David Talbot, ''[[MIT Technology Review]]''</ref> Another example is Facial Dysmorphology Novel Analysis (FDNA) used to analyze cases of human malformation connected to a large database of genetic syndromes. === Visual art processing === Closely related to the progress that has been made in image recognition is the increasing application of deep learning techniques to various visual art tasks. DNNs have proven themselves capable, for example, of a) identifying the style period of a given painting, b) [[Neural Style Transfer]] - capturing the style of a given artwork and applying it in a visually pleasing manner to an arbitrary photograph or video, and c) generating striking imagery based on random visual input fields.<ref>{{cite journal |author1=G. W. Smith|author2=Frederic Fol Leymarie|date=10 April 2017|title=The Machine as Artist: An Introduction|journal=Arts|volume=6|issue=4|pages=5|doi=10.3390/arts6020005}}</ref><ref>{{cite journal |author=Blaise Agüera y Arcas|date=29 September 2017|title=Art in the Age of Machine Intelligence|journal=Arts|volume=6|issue=4|pages=18|doi=10.3390/arts6040018}}</ref> === Natural language processing === {{Main|Natural language processing}} Neural networks have been used for implementing language models since the early 2000s.<ref name="gers2001" /><ref>{{Cite journal|last=Bengio|first=Yoshua|last2=Ducharme|first2=Réjean|last3=Vincent|first3=Pascal|last4=Janvin|first4=Christian|date=March 2003|title=A Neural Probabilistic Language Model|url=http://dl.acm.org/citation.cfm?id=944919.944966|journal=J. Mach. Learn. Res.|volume=3|pages=1137–1155|issn=1532-4435}}</ref> LSTM helped to improve machine translation and language modeling.<ref name="NIPS2014" /><ref name="vinyals2016" /><ref name="gillick2015" /> Other key techniques in this field are negative sampling<ref name="GoldbergLevy2014">{{cite arXiv|last1=Goldberg|first1=Yoav|last2=Levy|first2=Omar|title=word2vec Explained: Deriving Mikolov et al.'s Negative-Sampling Word-Embedding Method|eprint=1402.3722|class=cs.CL|year=2014}}</ref> and [[word embedding]]. Word embedding, such as ''[[word2vec]]'', can be thought of as a representational layer in a deep learning architecture that transforms an atomic word into a positional representation of the word relative to other words in the dataset; the position is represented as a point in a [[vector space]]. Using word embedding as an RNN input layer allows the network to parse sentences and phrases using an effective compositional vector grammar. A compositional vector grammar can be thought of as [[probabilistic context free grammar]] (PCFG) implemented by an RNN.<ref name="SocherManning2014">{{cite web|last1=Socher|first1=Richard|last2=Manning|first2=Christopher|title=Deep Learning for NLP|url=http://nlp.stanford.edu/courses/NAACL2013/NAACL2013-Socher-Manning-DeepLearning.pdf|accessdate=26 October 2014}}</ref> Recursive auto-encoders built atop word embeddings can assess sentence similarity and detect paraphrasing.<ref name="SocherManning2014" /> Deep neural architectures provide the best results for [[Statistical parsing|constituency parsing]],<ref>{{Cite journal |url= http://aclweb.org/anthology/P/P13/P13-1045.pdf|title = Parsing With Compositional Vector Grammars|last = Socher|first = Richard|date = 2013|journal = Proceedings of the ACL 2013 Conference|accessdate = |doi = |pmid = |last2 = Bauer|first2 = John|last3 = Manning|first3 = Christopher|last4 = Ng|first4 = Andrew}}</ref> [[sentiment analysis]],<ref>{{Cite journal |url= http://nlp.stanford.edu/~socherr/EMNLP2013_RNTN.pdf|title = Recursive Deep Models for Semantic Compositionality Over a Sentiment Treebank|last = Socher|first = Richard|date = 2013 |accessdate = |doi = |pmid =}}</ref> information retrieval,<ref>{{Cite journal|last=Shen|first=Yelong|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Mesnil|first5=Gregoire|date=2014-11-01|title=A Latent Semantic Model with Convolutional-Pooling Structure for Information Retrieval|url=https://www.microsoft.com/en-us/research/publication/a-latent-semantic-model-with-convolutional-pooling-structure-for-information-retrieval/|journal=Microsoft Research}}</ref><ref>{{Cite journal|last=Huang|first=Po-Sen|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Acero|first5=Alex|last6=Heck|first6=Larry|date=2013-10-01|title=Learning Deep Structured Semantic Models for Web Search using Clickthrough Data|url=https://www.microsoft.com/en-us/research/publication/learning-deep-structured-semantic-models-for-web-search-using-clickthrough-data/|journal=Microsoft Research}}</ref> spoken language understanding,<ref name="IEEE-TASL2015">{{cite journal | last1 = Mesnil | first1 = G. | last2 = Dauphin | first2 = Y. | last3 = Yao | first3 = K. | last4 = Bengio | first4 = Y. | last5 = Deng | first5 = L. | last6 = Hakkani-Tur | first6 = D. | last7 = He | first7 = X. | last8 = Heck | first8 = L. | last9 = Tur | first9 = G. | last10 = Yu | first10 = D. | last11 = Zweig | first11 = G. | year = 2015 | title = Using recurrent neural networks for slot filling in spoken language understanding | url= https://www.semanticscholar.org/paper/41911ef90a225a82597a2b576346759ea9c34247| journal = IEEE Transactions on Audio, Speech, and Language Processing | volume = 23 | issue = 3| pages = 530–539 | doi=10.1109/taslp.2014.2383614}}</ref> machine translation,<ref name="NIPS2014">{{Cite journal|last=Sutskever|first=L.|last2=Vinyals|first2=O.|last3=Le|first3=Q.|date=2014|title=Sequence to Sequence Learning with Neural Networks|url=https://papers.nips.cc/paper/5346-sequence-to-sequence-learning-with-neural-networks.pdf|journal=Proc. NIPS|pages=|via=|bibcode=2014arXiv1409.3215S|arxiv=1409.3215}}</ref><ref name="auto">{{Cite journal|last=Gao|first=Jianfeng|last2=He|first2=Xiaodong|last3=Yih|first3=Scott Wen-tau|last4=Deng|first4=Li|date=2014-06-01|title=Learning Continuous Phrase Representations for Translation Modeling|url=https://www.microsoft.com/en-us/research/publication/learning-continuous-phrase-representations-for-translation-modeling/|journal=Microsoft Research}}</ref> contextual entity linking,<ref name="auto"/> writing style recognition,<ref name="BROC2017">{{Cite journal |doi = 10.1002/dac.3259|title = Authorship verification using deep belief network systems|journal = International Journal of Communication Systems|volume = 30|issue = 12|pages = e3259|year = 2017|last1 = Brocardo|first1 = Marcelo Luiz|last2 = Traore|first2 = Issa|last3 = Woungang|first3 = Isaac|last4 = Obaidat|first4 = Mohammad S.}}</ref> Text classification and others.<ref>{{Cite news|url=https://www.microsoft.com/en-us/research/project/deep-learning-for-natural-language-processing-theory-and-practice-cikm2014-tutorial/|title=Deep Learning for Natural Language Processing: Theory and Practice (CIKM2014 Tutorial) - Microsoft Research|work=Microsoft Research|accessdate=2017-06-14}}</ref> Recent developments generalize [[word embedding]] to [[sentence embedding]]. [[Google Translate]] (GT) uses a large [[End-to-end principle|end-to-end]] long short-term memory network.<ref name="GT_Turovsky_2016">{{cite web|url=https://blog.google/products/translate/found-translation-more-accurate-fluent-sentences-google-translate/|title=Found in translation: More accurate, fluent sentences in Google Translate|last=Turovsky|first=Barak|date=November 15, 2016|website=The Keyword Google Blog|accessdate=March 23, 2017}}</ref><ref name="googleblog_GNMT_2016">{{cite web|url=https://research.googleblog.com/2016/11/zero-shot-translation-with-googles.html|title=Zero-Shot Translation with Google's Multilingual Neural Machine Translation System|last1=Schuster|first1=Mike|last2=Johnson|first2=Melvin|date=November 22, 2016|website=Google Research Blog|accessdate=March 23, 2017|last3=Thorat|first3=Nikhil}}</ref><ref name="lstm1997">{{Cite journal|author=Sepp Hochreiter|author2=Jürgen Schmidhuber|year=1997|title=Long short-term memory|url=https://www.researchgate.net/publication/13853244|journal=[[Neural Computation (journal)|Neural Computation]]|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|pmid=9377276|via=}}</ref><ref name="lstm2000">{{Cite journal|author=Felix A. Gers|author2=Jürgen Schmidhuber|author3=Fred Cummins|year=2000|title=Learning to Forget: Continual Prediction with LSTM|journal=[[Neural Computation (journal)|Neural Computation]]|volume=12|issue=10|pages=2451–2471|doi=10.1162/089976600300015015|pmid=11032042|citeseerx=10.1.1.55.5709|url=https://www.semanticscholar.org/paper/11540131eae85b2e11d53df7f1360eeb6476e7f4}}</ref><ref name="GoogleTranslate">{{cite arXiv |eprint=1609.08144|last1=Wu|first1=Yonghui|title=Google's Neural Machine Translation System: Bridging the Gap between Human and Machine Translation|last2=Schuster|first2=Mike|last3=Chen|first3=Zhifeng|last4=Le|first4=Quoc V|last5=Norouzi|first5=Mohammad|last6=Macherey|first6=Wolfgang|last7=Krikun|first7=Maxim|last8=Cao|first8=Yuan|last9=Gao|first9=Qin|last10=Macherey|first10=Klaus|last11=Klingner|first11=Jeff|last12=Shah|first12=Apurva|last13=Johnson|first13=Melvin|last14=Liu|first14=Xiaobing|last15=Kaiser|first15=Łukasz|last16=Gouws|first16=Stephan|last17=Kato|first17=Yoshikiyo|last18=Kudo|first18=Taku|last19=Kazawa|first19=Hideto|last20=Stevens|first20=Keith|last21=Kurian|first21=George|last22=Patil|first22=Nishant|last23=Wang|first23=Wei|last24=Young|first24=Cliff|last25=Smith|first25=Jason|last26=Riesa|first26=Jason|last27=Rudnick|first27=Alex|last28=Vinyals|first28=Oriol|last29=Corrado|first29=Greg|last30=Hughes|first30=Macduff|display-authors=29|class=cs.CL|year=2016}}</ref><ref name="WiredGoogleTranslate">"An Infusion of AI Makes Google Translate More Powerful Than Ever." Cade Metz, WIRED, Date of Publication: 09.27.16. https://www.wired.com/2016/09/google-claims-ai-breakthrough-machine-translation/</ref> [[Google Neural Machine Translation|Google Neural Machine Translation (GNMT)]] uses an [[example-based machine translation]] method in which the system "learns from millions of examples."<ref name="googleblog_GNMT_2016" /> It translates "whole sentences at a time, rather than pieces. Google Translate supports over one hundred languages.<ref name="googleblog_GNMT_2016" /> The network encodes the "semantics of the sentence rather than simply memorizing phrase-to-phrase translations".<ref name="googleblog_GNMT_2016" /><ref name="Biotet">{{cite web|url=http://www-clips.imag.fr/geta/herve.blanchon/Pdfs/NLP-KE-10.pdf|title=MT on and for the Web|last1=Boitet|first1=Christian|last2=Blanchon|first2=Hervé|date=2010|accessdate=December 1, 2016|last3=Seligman|first3=Mark|last4=Bellynck|first4=Valérie}}</ref> GT uses English as an intermediate between most language pairs.<ref name="Biotet" /> === Drug discovery and toxicology === {{For|more information|Drug discovery|Toxicology}} A large percentage of candidate drugs fail to win regulatory approval. These failures are caused by insufficient efficacy (on-target effect), undesired interactions (off-target effects), or unanticipated [[Toxicity|toxic effects]].<ref name="ARROWSMITH2013">{{Cite journal | pmid = 23903212 | year = 2013 | last1 = Arrowsmith | first1 = J | title = Trial watch: Phase II and phase III attrition rates 2011-2012 | journal = Nature Reviews Drug Discovery | volume = 12 | issue = 8 | pages = 569 | last2 = Miller | first2 = P | doi = 10.1038/nrd4090 | url = https://www.semanticscholar.org/paper/9ab0f468a64762ca5069335c776e1ab07fa2b3e2 }}</ref><ref name="VERBIEST2015">{{Cite journal | pmid = 25582842 | year = 2015 | last1 = Verbist | first1 = B | title = Using transcriptomics to guide lead optimization in drug discovery projects: Lessons learned from the QSTAR project | journal = Drug Discovery Today | last2 = Klambauer | first2 = G | last3 = Vervoort | first3 = L | last4 = Talloen | first4 = W | last5 = The Qstar | first5 = Consortium | last6 = Shkedy | first6 = Z | last7 = Thas | first7 = O | last8 = Bender | first8 = A | last9 = Göhlmann | first9 = H. W. | last10 = Hochreiter | first10 = S | doi = 10.1016/j.drudis.2014.12.014 | volume=20 | issue = 5 | pages=505–513 }}</ref> Research has explored use of deep learning to predict the [[biomolecular target]]s,<ref name="MERCK2012" /><ref name=":5" /> [[off-target]]s, and [[Toxicity|toxic effects]] of environmental chemicals in nutrients, household products and drugs.<ref name="TOX21" /><ref name="TOX21Data" /><ref name=":11" /> AtomNet is a deep learning system for structure-based [[Drug design|rational drug design]].<ref>{{cite arXiv|title = AtomNet: A Deep Convolutional Neural Network for Bioactivity Prediction in Structure-based Drug Discovery|eprint= 1510.02855|date = 2015-10-09|first = Izhar|last = Wallach|first2 = Michael|last2 = Dzamba|first3 = Abraham|last3 = Heifets|class= cs.LG}}</ref> AtomNet was used to predict novel candidate biomolecules for disease targets such as the [[Ebola virus]]<ref>{{Cite news|title = Toronto startup has a faster way to discover effective medicines |url= https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/|website = The Globe and Mail |accessdate= 2015-11-09}}</ref> and [[multiple sclerosis]].<ref>{{Cite web|title = Startup Harnesses Supercomputers to Seek Cures |url= http://ww2.kqed.org/futureofyou/2015/05/27/startup-harnesses-supercomputers-to-seek-cures/|website = KQED Future of You|accessdate = 2015-11-09}}</ref><ref>{{cite web|url=https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/%5D%20and%20multiple%20sclerosis%20%5B/|title=Toronto startup has a faster way to discover effective medicines}}</ref> In 2019 generative neural networks were used to produce molecules that were validated experimentally all the way into mice.<ref>{{cite journal |last1=Zhavoronkov |first1=Alex|date=2019|title=Deep learning enables rapid identification of potent DDR1 kinase inhibitors |journal=Nature Biotechnology |volume=37|issue=9|pages=1038–1040|doi=10.1038/s41587-019-0224-x |pmid=31477924|url=https://www.semanticscholar.org/paper/d44ac0a7fd4734187bccafc4a2771027b8bb595e}}</ref><ref>{{cite journal |last1=Gregory |first1=Barber |title=A Molecule Designed By AI Exhibits 'Druglike' Qualities |url=https://www.wired.com/story/molecule-designed-ai-exhibits-druglike-qualities/ |journal=Wired}}</ref> === Customer relationship management === {{Main|Customer relationship management}} Deep reinforcement learning has been used to approximate the value of possible [[direct marketing]] actions, defined in terms of [[RFM (customer value)|RFM]] variables. The estimated value function was shown to have a natural interpretation as [[customer lifetime value]].<ref>{{cite arxiv|last=Tkachenko |first=Yegor |title=Autonomous CRM Control via CLV Approximation with Deep Reinforcement Learning in Discrete and Continuous Action Space |date=April 8, 2015 |eprint=1504.01840|class=cs.LG }}</ref> === Recommendation systems === {{Main|Recommender system}} Recommendation systems have used deep learning to extract meaningful features for a latent factor model for content-based music and journal recommendations.<ref>{{Cite book|url=http://papers.nips.cc/paper/5004-deep-content-based-music-recommendation.pdf|title=Advances in Neural Information Processing Systems 26|last=van den Oord|first=Aaron|last2=Dieleman|first2=Sander|last3=Schrauwen|first3=Benjamin|date=2013|publisher=Curran Associates, Inc.|editor-last=Burges|editor-first=C. J. C.|pages=2643–2651|editor-last2=Bottou|editor-first2=L.|editor-last3=Welling|editor-first3=M.|editor-last4=Ghahramani|editor-first4=Z.|editor-last5=Weinberger|editor-first5=K. Q.}}</ref><ref>X.Y. Feng, H. Zhang, Y.J. Ren, P.H. Shang, Y. Zhu, Y.C. Liang, R.C. Guan, D. Xu, (2019), "[https://www.jmir.org/2019/5/e12957/ The Deep Learning–Based Recommender System “Pubmender” for Choosing a Biomedical Publication Venue: Development and Validation Study]", ''[[Journal of Medical Internet Research]]'', 21 (5): e12957</ref> Multiview deep learning has been applied for learning user preferences from multiple domains.<ref>{{Cite journal|last=Elkahky|first=Ali Mamdouh|last2=Song|first2=Yang|last3=He|first3=Xiaodong|date=2015-05-01|title=A Multi-View Deep Learning Approach for Cross Domain User Modeling in Recommendation Systems|url=https://www.microsoft.com/en-us/research/publication/a-multi-view-deep-learning-approach-for-cross-domain-user-modeling-in-recommendation-systems/|journal=Microsoft Research}}</ref> The model uses a hybrid collaborative and content-based approach and enhances recommendations in multiple tasks. === Bioinformatics === {{Main|Bioinformatics}} An [[autoencoder]] ANN was used in [[bioinformatics]], to predict [[Gene Ontology|gene ontology]] annotations and gene-function relationships.<ref>{{cite book|title=Deep Autoencoder Neural Networks for Gene Ontology Annotation Predictions |first1=Davide |last1=Chicco|first2=Peter|last2=Sadowski|first3=Pierre |last3=Baldi |date=1 January 2014|publisher=ACM|pages=533–540|doi=10.1145/2649387.2649442|journal=Proceedings of the 5th ACM Conference on Bioinformatics, Computational Biology, and Health Informatics - BCB '14|isbn=9781450328944 |hdl = 11311/964622|url=https://www.semanticscholar.org/paper/09f3132fdf103bdef1125ffbccb8b46f921b2ab7 }}</ref> In medical informatics, deep learning was used to predict sleep quality based on data from wearables<ref>{{Cite journal|last=Sathyanarayana|first=Aarti|date=2016-01-01|title=Sleep Quality Prediction From Wearable Data Using Deep Learning|journal=JMIR mHealth and uHealth|volume=4|issue=4|doi=10.2196/mhealth.6562|pmid=27815231|pmc=5116102|pages=e125|url=https://www.semanticscholar.org/paper/c82884f9d6d39c8a89ac46b8f688669fb2931144}}</ref> and predictions of health complications from [[electronic health record]] data.<ref>{{Cite journal|last=Choi|first=Edward|last2=Schuetz|first2=Andy|last3=Stewart|first3=Walter F.|last4=Sun|first4=Jimeng|date=2016-08-13|title=Using recurrent neural network models for early detection of heart failure onset|url=http://jamia.oxfordjournals.org/content/early/2016/08/13/jamia.ocw112|journal=Journal of the American Medical Informatics Association|volume=24|issue=2|pages=361–370|doi=10.1093/jamia/ocw112|issn=1067-5027|pmid=27521897|pmc=5391725}}</ref> Deep learning has also showed efficacy in [[Artificial intelligence in healthcare|healthcare]].<ref>{{Cite web|url=https://medium.com/the-mission/deep-learning-in-healthcare-challenges-and-opportunities-d2eee7e2545|title=Deep Learning in Healthcare: Challenges and Opportunities|date=2016-08-12|website=Medium|access-date=2018-04-10}}</ref> === Medical Image Analysis === Deep learning has been shown to produce competitive results in medical application such as cancer cell classification, lesion detection, organ segmentation and image enhancement<ref>{{Cite journal|last=Litjens|first=Geert|last2=Kooi|first2=Thijs|last3=Bejnordi|first3=Babak Ehteshami|last4=Setio|first4=Arnaud Arindra Adiyoso|last5=Ciompi|first5=Francesco|last6=Ghafoorian|first6=Mohsen|last7=van der Laak|first7=Jeroen A.W.M.|last8=van Ginneken|first8=Bram|last9=Sánchez|first9=Clara I.|date=December 2017|title=A survey on deep learning in medical image analysis|journal=Medical Image Analysis|volume=42|pages=60–88|doi=10.1016/j.media.2017.07.005|pmid=28778026|arxiv=1702.05747|bibcode=2017arXiv170205747L|url=https://www.semanticscholar.org/paper/2abde28f75a9135c8ed7c50ea16b7b9e49da0c09}}</ref><ref>{{Cite book |doi=10.1109/ICCVW.2017.18|isbn=9781538610343|chapter=Deep Convolutional Neural Networks for Detecting Cellular Changes Due to Malignancy|title=2017 IEEE International Conference on Computer Vision Workshops (ICCVW)|pages=82–89|year=2017|last1=Forslid|first1=Gustav|last2=Wieslander|first2=Hakan|last3=Bengtsson|first3=Ewert|last4=Wahlby|first4=Carolina|last5=Hirsch|first5=Jan-Michael|last6=Stark|first6=Christina Runow|last7=Sadanandan|first7=Sajith Kecheril|chapter-url=http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326160|url=https://www.semanticscholar.org/paper/6ae67bb4528bd5d922fd5a0c1a180ff1940f803c}}</ref> === Mobile advertising === Finding the appropriate mobile audience for [[mobile advertising]] is always challenging, since many data points must be considered and analyzed before a target segment can be created and used in ad serving by any ad server.<ref>{{cite book |doi=10.1109/CSCITA.2017.8066548 |isbn=978-1-5090-4381-1|chapter=Predicting the popularity of instagram posts for a lifestyle magazine using deep learning|title=2017 2nd International Conference on Communication Systems, Computing and IT Applications (CSCITA)|pages=174–177|year=2017|last1=De|first1=Shaunak|last2=Maity|first2=Abhishek|last3=Goel|first3=Vritti|last4=Shitole|first4=Sanjay|last5=Bhattacharya|first5=Avik|chapter-url=https://www.semanticscholar.org/paper/c4389f8a63a7be58e007c183a49e491141f9e204}}</ref> Deep learning has been used to interpret large, many-dimensioned advertising datasets. Many data points are collected during the request/serve/click internet advertising cycle. This information can form the basis of machine learning to improve ad selection. === Image restoration === Deep learning has been successfully applied to [[inverse problems]] such as [[denoising]], [[super-resolution]], [[inpainting]], and [[film colorization]].<ref>{{Cite web|url=https://blog.floydhub.com/colorizing-and-restoring-old-images-with-deep-learning/|title=Colorizing and Restoring Old Images with Deep Learning|date=2018-11-13|website=FloydHub Blog|language=en|access-date=2019-10-11}}</ref> These applications include learning methods such as "Shrinkage Fields for Effective Image Restoration"<ref>{{cite conference | url= http://research.uweschmidt.org/pubs/cvpr14schmidt.pdf |first1= Uwe |last1= Schmidt |first2= Stefan |last2= Roth |conference= Computer Vision and Pattern Recognition (CVPR), 2014 IEEE Conference on |title= Shrinkage Fields for Effective Image Restoration }}</ref> which trains on an image dataset, and [[Deep Image Prior]], which trains on the image that needs restoration. === Financial fraud detection === Deep learning is being successfully applied to financial [[fraud detection]] and anti-money laundering. "Deep anti-money laundering detection system can spot and recognize relationships and similarities between data and, further down the road, learn to detect anomalies or classify and predict specific events". The solution leverages both supervised learning techniques, such as the classification of suspicious transactions, and unsupervised learning, e.g. anomaly detection. <ref>{{cite journal |first=Tomasz |last=Czech |title=Deep learning: the next frontier for money laundering detection |url=https://www.globalbankingandfinance.com/deep-learning-the-next-frontier-for-money-laundering-detection/ |journal=Global Banking and Finance Review }}</ref> === Military === The United States Department of Defense applied deep learning to train robots in new tasks through observation.<ref name=":12">{{Cite web|url=https://www.eurekalert.org/pub_releases/2018-02/uarl-ard020218.php|title=Army researchers develop new algorithms to train robots|website=EurekAlert!|access-date=2018-08-29}}</ref> == Relation to human cognitive and brain development == Deep learning is closely related to a class of theories of [[brain development]] (specifically, neocortical development) proposed by [[cognitive neuroscientist]]s in the early 1990s.<ref name="UTGOFF">{{cite journal | last1 = Utgoff | first1 = P. E. | last2 = Stracuzzi | first2 = D. J. | year = 2002 | title = Many-layered learning | url= https://www.semanticscholar.org/paper/398c477f674b228fec7f3f418a8cec047e2dafe5| journal = Neural Computation | volume = 14 | issue = 10| pages = 2497–2529 | doi=10.1162/08997660260293319| pmid = 12396572 }}</ref><ref name="ELMAN">{{cite book|url={{google books |plainurl=y |id=vELaRu_MrwoC}}|title=Rethinking Innateness: A Connectionist Perspective on Development|last=Elman|first=Jeffrey L.|publisher=MIT Press|year=1998|isbn=978-0-262-55030-7}}</ref><ref name="SHRAGER">{{cite journal | last1 = Shrager | first1 = J. | last2 = Johnson | first2 = MH | year = 1996 | title = Dynamic plasticity influences the emergence of function in a simple cortical array | url= | journal = Neural Networks | volume = 9 | issue = 7| pages = 1119–1129 | doi=10.1016/0893-6080(96)00033-0| pmid = 12662587 }}</ref><ref name="QUARTZ">{{cite journal | last1 = Quartz | first1 = SR | last2 = Sejnowski | first2 = TJ | year = 1997 | title = The neural basis of cognitive development: A constructivist manifesto | url= | journal = Behavioral and Brain Sciences | volume = 20 | issue = 4| pages = 537–556 | doi=10.1017/s0140525x97001581| pmid = 10097006 | citeseerx = 10.1.1.41.7854 }}</ref> These developmental theories were instantiated in computational models, making them predecessors of deep learning systems. These developmental models share the property that various proposed learning dynamics in the brain (e.g., a wave of [[nerve growth factor]]) support the [[self-organization]] somewhat analogous to the neural networks utilized in deep learning models. Like the [[neocortex]], neural networks employ a hierarchy of layered filters in which each layer considers information from a prior layer (or the operating environment), and then passes its output (and possibly the original input), to other layers. This process yields a self-organizing stack of [[transducer]]s, well-tuned to their operating environment. A 1995 description stated, "...the infant's brain seems to organize itself under the influence of waves of so-called trophic-factors ... different regions of the brain become connected sequentially, with one layer of tissue maturing before another and so on until the whole brain is mature."<ref name="BLAKESLEE">S. Blakeslee., "In brain's early growth, timetable may be critical," ''The New York Times, Science Section'', pp. B5–B6, 1995.</ref> A variety of approaches have been used to investigate the plausibility of deep learning models from a neurobiological perspective. On the one hand, several variants of the [[backpropagation]] algorithm have been proposed in order to increase its processing realism.<ref>{{Cite journal|last=Mazzoni|first=P.|last2=Andersen|first2=R. A.|last3=Jordan|first3=M. I.|date=1991-05-15|title=A more biologically plausible learning rule for neural networks.|journal=Proceedings of the National Academy of Sciences|volume=88|issue=10|pages=4433–4437|doi=10.1073/pnas.88.10.4433|issn=0027-8424|pmid=1903542|pmc=51674|bibcode=1991PNAS...88.4433M}}</ref><ref>{{Cite journal|last=O'Reilly|first=Randall C.|date=1996-07-01|title=Biologically Plausible Error-Driven Learning Using Local Activation Differences: The Generalized Recirculation Algorithm|journal=Neural Computation|volume=8|issue=5|pages=895–938|doi=10.1162/neco.1996.8.5.895|issn=0899-7667|url=https://www.semanticscholar.org/paper/ed9133009dd451bd64215cca7deba6e0b8d7c7b1}}</ref> Other researchers have argued that unsupervised forms of deep learning, such as those based on hierarchical [[generative model]]s and [[deep belief network]]s, may be closer to biological reality.<ref>{{Cite journal|last=Testolin|first=Alberto|last2=Zorzi|first2=Marco|date=2016|title=Probabilistic Models and Generative Neural Networks: Towards an Unified Framework for Modeling Normal and Impaired Neurocognitive Functions|journal=Frontiers in Computational Neuroscience|volume=10|pages=73|doi=10.3389/fncom.2016.00073|pmid=27468262|pmc=4943066|issn=1662-5188|url=https://www.semanticscholar.org/paper/9ff36a621ee2c831fbbda5b719942f9ed8ac844f}}</ref><ref>{{Cite journal|last=Testolin|first=Alberto|last2=Stoianov|first2=Ivilin|last3=Zorzi|first3=Marco|date=September 2017|title=Letter perception emerges from unsupervised deep learning and recycling of natural image features|journal=Nature Human Behaviour|volume=1|issue=9|pages=657–664|doi=10.1038/s41562-017-0186-2|pmid=31024135|issn=2397-3374|url=https://www.semanticscholar.org/paper/ec2463bd610dcb30d67681160e895761e2dde482}}</ref> In this respect, generative neural network models have been related to neurobiological evidence about sampling-based processing in the cerebral cortex.<ref>{{Cite journal|last=Buesing|first=Lars|last2=Bill|first2=Johannes|last3=Nessler|first3=Bernhard|last4=Maass|first4=Wolfgang|date=2011-11-03|title=Neural Dynamics as Sampling: A Model for Stochastic Computation in Recurrent Networks of Spiking Neurons|journal=PLOS Computational Biology|volume=7|issue=11|pages=e1002211|doi=10.1371/journal.pcbi.1002211|pmid=22096452|pmc=3207943|issn=1553-7358|bibcode=2011PLSCB...7E2211B|url=https://www.semanticscholar.org/paper/e4e100e44bf7618c7d96188605fd9870012bdb50}}</ref> Although a systematic comparison between the human brain organization and the neuronal encoding in deep networks has not yet been established, several analogies have been reported. For example, the computations performed by deep learning units could be similar to those of actual neurons<ref>{{Cite journal|last=Morel|first=Danielle|last2=Singh|first2=Chandan|last3=Levy|first3=William B.|date=2018-01-25|title=Linearization of excitatory synaptic integration at no extra cost|journal=Journal of Computational Neuroscience|volume=44|issue=2|pages=173–188|doi=10.1007/s10827-017-0673-5|pmid=29372434|issn=0929-5313|url=https://www.semanticscholar.org/paper/3a528f2cde957d4e6417651f8005ca2ee81ca367}}</ref><ref>{{Cite journal|last=Cash|first=S.|last2=Yuste|first2=R.|date=February 1999|title=Linear summation of excitatory inputs by CA1 pyramidal neurons|journal=Neuron|volume=22|issue=2|pages=383–394|issn=0896-6273|pmid=10069343|doi=10.1016/s0896-6273(00)81098-3}}</ref> and neural populations.<ref>{{Cite journal|date=2004-08-01|title=Sparse coding of sensory inputs|journal=Current Opinion in Neurobiology|volume=14|issue=4|pages=481–487|doi=10.1016/j.conb.2004.07.007|pmid=15321069|issn=0959-4388 | last1 = Olshausen | first1 = B | last2 = Field | first2 = D|url=https://www.semanticscholar.org/paper/0dd289358b14f8176adb7b62bf2fb53ea62b3818}}</ref> Similarly, the representations developed by deep learning models are similar to those measured in the primate visual system<ref>{{Cite journal|last=Yamins|first=Daniel L K|last2=DiCarlo|first2=James J|date=March 2016|title=Using goal-driven deep learning models to understand sensory cortex|journal=Nature Neuroscience|volume=19|issue=3|pages=356–365|doi=10.1038/nn.4244|pmid=26906502|issn=1546-1726|url=https://www.semanticscholar.org/paper/94c4ba7246f781632aa68ca5b1acff0fdbb2d92f}}</ref> both at the single-unit<ref>{{Cite journal|last=Zorzi|first=Marco|last2=Testolin|first2=Alberto|date=2018-02-19|title=An emergentist perspective on the origin of number sense|journal=Phil. Trans. R. Soc. B|volume=373|issue=1740|pages=20170043|doi=10.1098/rstb.2017.0043|issn=0962-8436|pmid=29292348|pmc=5784047|url=https://www.semanticscholar.org/paper/c91db0c8349a78384f54c6a9a98370f5c9381b6c}}</ref> and at the population<ref>{{Cite journal|last=Güçlü|first=Umut|last2=van Gerven|first2=Marcel A. J.|date=2015-07-08|title=Deep Neural Networks Reveal a Gradient in the Complexity of Neural Representations across the Ventral Stream|journal=Journal of Neuroscience|volume=35|issue=27|pages=10005–10014|doi=10.1523/jneurosci.5023-14.2015|pmid=26157000|pmc=6605414|arxiv=1411.6422}}</ref> levels. == Commercial activity == [[Facebook]]'s AI lab performs tasks such as [[Automatic image annotation|automatically tagging uploaded pictures]] with the names of the people in them.<ref name="METZ2013">{{cite magazine|first=C. |last=Metz |title=Facebook's 'Deep Learning' Guru Reveals the Future of AI |url=https://www.wired.com/wiredenterprise/2013/12/facebook-yann-lecun-qa/ |magazine=Wired |date=12 December 2013}}</ref> Google's [[DeepMind Technologies]] developed a system capable of learning how to play [[Atari]] video games using only pixels as data input. In 2015 they demonstrated their [[AlphaGo]] system, which learned the game of [[Go (game)|Go]] well enough to beat a professional Go player.<ref>{{Cite web|title = Google AI algorithm masters ancient game of Go |url= http://www.nature.com/news/google-ai-algorithm-masters-ancient-game-of-go-1.19234|website = Nature News & Comment|accessdate = 2016-01-30}}</ref><ref>{{Cite journal|title = Mastering the game of Go with deep neural networks and tree search|journal = [[Nature (journal)|Nature]]| issn= 0028-0836|pages = 484–489|volume = 529|issue = 7587|doi = 10.1038/nature16961|pmid = 26819042|first1 = David|last1 = Silver|author-link1=David Silver (programmer)|first2 = Aja|last2 = Huang|author-link2=Aja Huang|first3 = Chris J.|last3 = Maddison|first4 = Arthur|last4 = Guez|first5 = Laurent|last5 = Sifre|first6 = George van den|last6 = Driessche|first7 = Julian|last7 = Schrittwieser|first8 = Ioannis|last8 = Antonoglou|first9 = Veda|last9 = Panneershelvam|first10= Marc|last10= Lanctot|first11= Sander|last11= Dieleman|first12=Dominik|last12= Grewe|first13= John|last13= Nham|first14= Nal|last14= Kalchbrenner|first15= Ilya|last15= Sutskever|author-link15=Ilya Sutskever|first16= Timothy|last16= Lillicrap|first17= Madeleine|last17= Leach|first18= Koray|last18= Kavukcuoglu|first19= Thore|last19= Graepel|first20= Demis |last20=Hassabis|author-link20=Demis Hassabis|date= 28 January 2016|bibcode = 2016Natur.529..484S|url = https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}{{closed access}}</ref><ref>{{Cite web|title = A Google DeepMind Algorithm Uses Deep Learning and More to Master the Game of Go {{!}} MIT Technology Review |url= http://www.technologyreview.com/news/546066/googles-ai-masters-the-game-of-go-a-decade-earlier-than-expected/|website = MIT Technology Review|accessdate = 2016-01-30}}</ref> [[Google Translate]] uses a neural network to translate between more than 100 languages. In 2015, [[Blippar]] demonstrated a mobile [[augmented reality]] application that uses deep learning to recognize objects in real time.<ref>{{Cite web|title=Blippar Demonstrates New Real-Time Augmented Reality App|url=https://techcrunch.com/2015/12/08/blippar-demonstrates-new-real-time-augmented-reality-app/|website=TechCrunch}}</ref> In 2017, Covariant.ai was launched, which focuses on integrating deep learning into factories.<ref>[https://www.nytimes.com/2017/11/06/technology/artificial-intelligence-start-up.html A.I. Researchers Leave Elon Musk Lab to Begin Robotics Start-Up]</ref> As of 2008,<ref>{{Cite document|title=TAMER: Training an Agent Manually via Evaluative Reinforcement - IEEE Conference Publication|doi=10.1109/DEVLRN.2008.4640845}}</ref> researchers at [[University of Texas at Austin|The University of Texas at Austin]] (UT) developed a machine learning framework called Training an Agent Manually via Evaluative Reinforcement, or TAMER, which proposed new methods for robots or computer programs to learn how to perform tasks by interacting with a human instructor.<ref name=":12" /> First developed as TAMER, a new algorithm called Deep TAMER was later introduced in 2018 during a collaboration between [[U.S. Army Research Laboratory]] (ARL) and UT researchers. Deep TAMER used deep learning to provide a robot the ability to learn new tasks through observation.<ref name=":12" /> Using Deep TAMER, a robot learned a task with a human trainer, watching video streams or observing a human perform a task in-person. The robot later practiced the task with the help of some coaching from the trainer, who provided feedback such as “good job” and “bad job.”<ref>{{Cite web|url=https://governmentciomedia.com/talk-algorithms-ai-becomes-faster-learner|title=Talk to the Algorithms: AI Becomes a Faster Learner|website=governmentciomedia.com|access-date=2018-08-29}}</ref> == Criticism and comment == Deep learning has attracted both criticism and comment, in some cases from outside the field of computer science. === Theory === {{see also|Explainable AI}} A main criticism concerns the lack of theory surrounding some methods.<ref>{{Cite web|url=https://medium.com/@GaryMarcus/in-defense-of-skepticism-about-deep-learning-6e8bfd5ae0f1|title=In defense of skepticism about deep learning|last=Marcus|first=Gary|date=2018-01-14|website=Gary Marcus|access-date=2018-10-11}}</ref> Learning in the most common deep architectures is implemented using well-understood gradient descent. However, the theory surrounding other algorithms, such as contrastive divergence is less clear.{{citation needed|date=July 2016}} (e.g., Does it converge? If so, how fast? What is it approximating?) Deep learning methods are often looked at as a [[black box]], with most confirmations done empirically, rather than theoretically.<ref name="Knight 2017">{{cite web | last=Knight | first=Will | title=DARPA is funding projects that will try to open up AI's black boxes | website=MIT Technology Review | date=2017-03-14 | url=https://www.technologyreview.com/s/603795/the-us-military-wants-its-autonomous-machines-to-explain-themselves/ | accessdate=2017-11-02}}</ref> Others point out that deep learning should be looked at as a step towards realizing strong AI, not as an all-encompassing solution. Despite the power of deep learning methods, they still lack much of the functionality needed for realizing this goal entirely. Research psychologist Gary Marcus noted:<blockquote>"Realistically, deep learning is only part of the larger challenge of building intelligent machines. Such techniques lack ways of representing [[causality|causal relationships]] (...) have no obvious ways of performing [[inference|logical inferences]], and they are also still a long way from integrating abstract knowledge, such as information about what objects are, what they are for, and how they are typically used. The most powerful A.I. systems, like [[Watson (computer)|Watson]] (...) use techniques like deep learning as just one element in a very complicated ensemble of techniques, ranging from the statistical technique of [[Bayesian inference]] to [[deductive reasoning]]."<ref>{{cite magazine|url=https://www.newyorker.com/|title=Is "Deep Learning" a Revolution in Artificial Intelligence?|last=Marcus|first=Gary|date=November 25, 2012|magazine=The New Yorker|accessdate=2017-06-14}}</ref></blockquote>As an alternative to this emphasis on the limits of deep learning, one author speculated that it might be possible to train a machine vision stack to perform the sophisticated task of discriminating between "old master" and amateur figure drawings, and hypothesized that such a sensitivity might represent the rudiments of a non-trivial machine empathy.<ref>{{cite web|url=http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|title=Art and Artificial Intelligence|date=March 27, 2015|publisher=ArtEnt|author=Smith, G. W.|accessdate=March 27, 2015|url-status=bot: unknown|archiveurl=https://web.archive.org/web/20170625075845/http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|archivedate=June 25, 2017}}</ref> This same author proposed that this would be in line with anthropology, which identifies a concern with aesthetics as a key element of [[behavioral modernity]].<ref>{{cite web |url=http://repositriodeficheiros.yolasite.com/resources/Texto%2028.pdf |author=Mellars, Paul |date=February 1, 2005 |title=The Impossible Coincidence: A Single-Species Model for the Origins of Modern Human Behavior in Europe|publisher=Evolutionary Anthropology: Issues, News, and Reviews |accessdate=April 5, 2017}}</ref> In further reference to the idea that artistic sensitivity might inhere within relatively low levels of the cognitive hierarchy, a published series of graphic representations of the internal states of deep (20-30 layers) neural networks attempting to discern within essentially random data the images on which they were trained<ref>{{cite web|url=http://googleresearch.blogspot.co.uk/2015/06/inceptionism-going-deeper-into-neural.html |author1=Alexander Mordvintsev |author2=Christopher Olah |author3=Mike Tyka |date=June 17, 2015 |title=Inceptionism: Going Deeper into Neural Networks |publisher=Google Research Blog |accessdate=June 20, 2015}}</ref> demonstrate a visual appeal: the original research notice received well over 1,000 comments, and was the subject of what was for a time the most frequently accessed article on ''[[The Guardian]]'s''<ref>{{cite news|url=https://www.theguardian.com/technology/2015/jun/18/google-image-recognition-neural-network-androids-dream-electric-sheep|title=Yes, androids do dream of electric sheep|date=June 18, 2015|newspaper=The Guardian|author=Alex Hern|accessdate=June 20, 2015}}</ref> website. === Errors === Some deep learning architectures display problematic behaviors,<ref name=goertzel>{{cite web|first=Ben |last=Goertzel |title=Are there Deep Reasons Underlying the Pathologies of Today's Deep Learning Algorithms? |year=2015 |url=http://goertzel.org/DeepLearning_v1.pdf}}</ref> such as confidently classifying unrecognizable images as belonging to a familiar category of ordinary images<ref>{{cite arxiv |eprint=1412.1897|last1=Nguyen|first1=Anh|title=Deep Neural Networks are Easily Fooled: High Confidence Predictions for Unrecognizable Images|last2=Yosinski|first2=Jason|last3=Clune|first3=Jeff|class=cs.CV|year=2014}}</ref> and misclassifying minuscule perturbations of correctly classified images.<ref>{{cite arxiv |eprint=1312.6199|last1=Szegedy|first1=Christian|title=Intriguing properties of neural networks|last2=Zaremba|first2=Wojciech|last3=Sutskever|first3=Ilya|last4=Bruna|first4=Joan|last5=Erhan|first5=Dumitru|last6=Goodfellow|first6=Ian|last7=Fergus|first7=Rob|class=cs.CV|year=2013}}</ref> [[Ben Goertzel|Goertzel]] hypothesized that these behaviors are due to limitations in their internal representations and that these limitations would inhibit integration into heterogeneous multi-component [[artificial general intelligence]] (AGI) architectures.<ref name="goertzel" /> These issues may possibly be addressed by deep learning architectures that internally form states homologous to image-grammar<ref>{{cite journal | last1 = Zhu | first1 = S.C. | last2 = Mumford | first2 = D. | year = 2006| title = A stochastic grammar of images | url= | journal = Found. Trends Comput. Graph. Vis. | volume = 2 | issue = 4| pages = 259–362 | doi = 10.1561/0600000018| citeseerx = 10.1.1.681.2190 }}</ref> decompositions of observed entities and events.<ref name="goertzel"/> [[Grammar induction|Learning a grammar]] (visual or linguistic) from training data would be equivalent to restricting the system to [[commonsense reasoning]] that operates on concepts in terms of grammatical [[Production (computer science)|production rules]] and is a basic goal of both human language acquisition<ref>Miller, G. A., and N. Chomsky. "Pattern conception." Paper for Conference on pattern detection, University of Michigan. 1957.</ref> and [[artificial intelligence]] (AI).<ref>{{cite web|first=Jason |last=Eisner |title=Deep Learning of Recursive Structure: Grammar Induction |url=http://techtalks.tv/talks/deep-learning-of-recursive-structure-grammar-induction/58089/}}</ref> === Cyber threat === As deep learning moves from the lab into the world, research and experience shows that artificial neural networks are vulnerable to hacks and deception.<ref>{{Cite web|url=https://gizmodo.com/hackers-have-already-started-to-weaponize-artificial-in-1797688425|title=Hackers Have Already Started to Weaponize Artificial Intelligence|website=Gizmodo|access-date=2019-10-11}}</ref> By identifying patterns that these systems use to function, attackers can modify inputs to ANNs in such a way that the ANN finds a match that human observers would not recognize. For example, an attacker can make subtle changes to an image such that the ANN finds a match even though the image looks to a human nothing like the search target. Such a manipulation is termed an “adversarial attack.”<ref>{{Cite web|url=https://www.dailydot.com/debug/adversarial-attacks-ai-mistakes/|title=How hackers can force AI to make dumb mistakes|date=2018-06-18|website=The Daily Dot|language=en|access-date=2019-10-11}}</ref> In 2016 researchers used one ANN to doctor images in trial and error fashion, identify another's focal points and thereby generate images that deceived it. The modified images looked no different to human eyes. Another group showed that printouts of doctored images then photographed successfully tricked an image classification system.<ref name=":4">{{Cite news|url=https://singularityhub.com/2017/10/10/ai-is-easy-to-fool-why-that-needs-to-change|title=AI Is Easy to Fool—Why That Needs to Change|last=|first=|date=2017-10-10|work=Singularity Hub|accessdate=2017-10-11}}</ref> One defense is reverse image search, in which a possible fake image is submitted to a site such as [[TinEye]] that can then find other instances of it. A refinement is to search using only parts of the image, to identify images from which that piece may have been taken'''.'''<ref>{{Cite journal|last=Gibney|first=Elizabeth|title=The scientist who spots fake videos|url=https://www.nature.com/news/the-scientist-who-spots-fake-videos-1.22784|journal=Nature|pages=|doi=10.1038/nature.2017.22784|via=|year=2017}}</ref> Another group showed that certain [[Psychedelic art|psychedelic]] spectacles could fool a [[facial recognition system]] into thinking ordinary people were celebrities, potentially allowing one person to impersonate another. In 2017 researchers added stickers to [[stop sign]]s and caused an ANN to misclassify them.<ref name=":4" /> ANNs can however be further trained to detect attempts at deception, potentially leading attackers and defenders into an arms race similar to the kind that already defines the [[malware]] defense industry. ANNs have been trained to defeat ANN-based anti-malware software by repeatedly attacking a defense with malware that was continually altered by a [[genetic algorithm]] until it tricked the anti-malware while retaining its ability to damage the target.<ref name=":4" /> Another group demonstrated that certain sounds could make the [[Google Now]] voice command system open a particular web address that would download malware.<ref name=":4" /> In “data poisoning,” false data is continually smuggled into a machine learning system's training set to prevent it from achieving mastery.<ref name=":4" /> === Reliance on human [[microwork]] === Most Deep Learning systems rely on training and verification data that is generated and/or annotated by humans. It has been argued in [[Media studies|media philosophy]] that not only low-paid [[Clickworkers|clickwork]] (e.g. on [[Amazon Mechanical Turk]]) is regularly deployed for this purpose, but also implicit forms of human [[microwork]] that are often not recognized as such.<ref name=":13">{{Cite journal|last=Mühlhoff|first=Rainer|date=2019-11-06|title=Human-aided artificial intelligence: Or, how to run large computations in human brains? Toward a media sociology of machine learning|journal=New Media & Society|language=en|volume=|pages=146144481988533|doi=10.1177/1461444819885334|issn=1461-4448}}</ref> The philosopher Rainer Mühlhoff distinguishes five types of "machinic capture" of human microwork to generate training data: (1) [[gamification]] (the embedding of annotation or computation tasks in the flow of a game), (2) "trapping and tracking" (e.g. [[CAPTCHA]]s for image recognition or click-tracking on Google [[Search engine results page|search results pages]]), (3) exploitation of social motivations (e.g. [[Tag (Facebook)|tagging faces]] on [[Facebook]] to obtain labeled facial images), (4) [[information mining]] (e.g. by leveraging [[Quantified self|quantified-self]] devices such as [[activity tracker]]s) and (5) [[Clickworkers|clickwork]].<ref name=":13" /> Mühlhoff argues that in most commercial end-user applications of Deep Learning such as [[DeepFace|Facebook's face recognition system,]] the need for training data does not stop once an ANN is trained. Rather, there is a continued demand for human-generated verification data to constantly calibrate and update the ANN. For this purpose Facebook introduced the feature that once a user is automatically recognized in an image, they receive a notification. They can choose whether of not they like to be publicly labeled on the image, or tell Facebook that it is not them in the picture.<ref>{{Cite news|url=https://www.wired.com/story/facebook-will-find-your-face-even-when-its-not-tagged/|title=Facebook Can Now Find Your Face, Even When It's Not Tagged|work=Wired|access-date=2019-11-22|language=en|issn=1059-1028}}</ref> This user interface is a mechanism to generate "a constant stream of  verification data"<ref name=":13" /> to further train the network in real-time. As Mühlhoff argues, involvement of human users to generate training and verification data is so typical for most commercial end-user applications of Deep Learning that such systems may be referred to as "human-aided artificial intelligence".<ref name=":13" /> == Shallowing deep neural networks == {{technical|section|date=February 2020}} Shallowing refers to reducing a pre-trained DNN to a smaller network with the same or similar performance.<ref>{{cite journal |last1= Chen|first1= S.|last2= Zhao|first2=Q.|date= 2018|title=Shallowing deep networks: Layer-wise pruning based on feature representations |url= |journal=Representations. IEEE Transactions on Pattern Analysis and Machine Intelligence |volume= 41|issue=12 |pages= 3048–56|doi=10.1109/TPAMI.2018.2874634 |pmid= 30296213|access-date=}}</ref> Training of DNN with further shallowing can produce more efficient systems than just training of smaller networks from scratch. Shallowing is the rebirth of pruning that developed in the 1980-1990s.<ref name= "Hassibi1993">{{cite conference | url = | title = Optimal brain surgeon and general network pruning | last1 = Hassibi | first1 = B. | last2 = Stork | first2 = D. G. | last3 = Wolff | first3 = G. J. | date = 1993 | publisher = IEEE | book-title = IEEE International Conference on Neural Networks | pages = 293–299 | volume = 1 | location = San Francisco, CA, USA | doi = 10.1109/ICNN.1993.298572 }}</ref><ref name= "Gordienko1993"> {{cite conference | url = | title = Construction of efficient neural networks: algorithms and tests | last1 = Gordienko | first1 = P. | date = 1993 | publisher = IEEE | book-title = Proceedings of 1993 International Conference on Neural Networks (IJCNN-93) | pages = 313–6 | volume = 1 | location = Nagoya, Japan | doi = 10.1109/IJCNN.1993.713920 }}</ref> The main approach to pruning is to gradually remove network elements (synapses, neurons, blocks of neurons, or layers) that have little impact on performance evaluation. Various indicators of sensitivity are used that estimate the changes of performance after pruning. The simplest indicators use just values of transmitted signals and the synaptic weights (the zeroth order). More complex indicators use mean absolute values of partial derivatives of the cost function,<ref name= "Gordienko1993"/><ref name="GorbMirTsar1999">{{cite conference | url = | title = Generation of explicit knowledge from empirical data through pruning of trainable neural networks | last1 = Gorban | first1 = A. N. | last2 = Mirkes | first2 = E. M. | last3 = Tsaregorodtsev | first3 = V. G. | date = 1999 | publisher = IEEE | book-title = IJCNN'99. International Joint Conference on Neural Networks. Proceedings (Cat. No.99CH36339) | pages = 4393–4398 | location = Washington, DC, USA | doi = 10.1109/IJCNN.1999.830876 | arxiv = cond-mat/0307083 }}</ref> or even the second derivatives.<ref name= "Hassibi1993"/> The shallowing allows to reduce the necessary resources and makes the skills of neural network more explicit.<ref name="GorbMirTsar1999"/> It is used for image classification,<ref>{{cite journal |last1=Zhong |first1= G.|last2= Yan|first2= S.|last3= Huang|first3= K.|last4=Cai|first4=Y.|last5=Dong |first5= J.|date=2018|title= Reducing and stretching deep convolutional activation features for accurate image classification|url= |journal= Cogn. Comput.|volume= 10|issue= 1|pages=179–86|doi=10.1007/s12559-017-9515-z |access-date=}}</ref> for development of security systems,<ref name="MirkesDog2019">{{cite journal |last1=Gorban |first1= A. N.|last2=Mirkes |first2=E. M. |last3=Tyukin |first3= I. Y.|date= 2019|title=How deep should be the depth of convolutional neural networks: A backyard dog case study |url= |journal=Cogn. Comput.|volume= |issue= |pages= |doi= 10.1007/s12559-019-09667-7 | doi-access= free| arxiv= 1805.01516 }}</ref> for accelerating DNN execution on mobile devices,<ref>{{cite conference | url = https://www.aaai.org/ocs/index.php/AAAI/AAAI18/paper/viewFile/16652/15946 | title = DeepRebirth: Accelerating deep neural network execution on mobile devices | last1 = Li | first1 = D. | last2 = Wang | first2 = X. | last3 = Kong | first3 = D. | date = 2018 | publisher = Association for the Advancement of Artificial Intelligence | book-title = Thirty-second AAAI conference on artificial intelligence (AAAI-18) | pages = | location = | doi = | arxiv = 1708.04728 }} </ref> and for other applications. It has been demonstrated that using linear postprocessing, such as supervised PCA, improves DNN performance after shallowing.<ref name="MirkesDog2019"/> == See also == * [[Applications of artificial intelligence]] * [[Comparison of deep learning software]] * [[Compressed sensing]] * [[Echo state network]] * [[List of artificial intelligence projects]] * [[Liquid state machine]] * [[List of datasets for machine learning research]] * [[Reservoir computing]] * [[Sparse coding]] == References == {{Reflist|30em}} == Further reading == {{refbegin}} * {{cite book |title=Deep Learning |year=2016 |first1=Ian |last1=Goodfellow |authorlink1=Ian Goodfellow |first2=Yoshua |last2=Bengio |authorlink2=Yoshua Bengio |first3=Aaron |last3=Courville |publisher=MIT Press |url=http://www.deeplearningbook.org |isbn=978-0-26203561-3 |postscript=, introductory textbook. }} {{Prone to spam|date=June 2015}}{{Z148}}<!-- {{No more links}} Please be cautious adding more external links. Wikipedia is not a collection of links and should not be used for advertising. Excessive or inappropriate links will be removed. See [[Wikipedia:External links]] and [[Wikipedia:Spam]] for details. If there are already suitable links, propose additions or replacements on the article's talk page, or submit your link to the relevant category at DMOZ (dmoz.org) and link there using {{Dmoz}}. --> [[Category:Deep learning| ]] [[Category:Artificial neural networks]] [[Category:Artificial intelligence]] [[Category:Emerging technologies]]'
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'@@ -1,455 +1,9 @@ -{{About||deep versus shallow learning in educational psychology|Student approaches to learning|more information|Artificial neural network}} -{{short description|Branch of machine learning}} +[http://204.152.217.73/ Agen Poker Terpercaya] -{{machine learning bar}} +[http://204.152.217.73/ Situs BandarQ Online] -'''Deep learning''' (also known as '''deep structured learning''' or '''differential programming''') is part of a broader family of [[machine learning]] methods based on [[artificial neural networks]] with [[representation learning]]. Learning can be [[Supervised learning|supervised]], [[Semi-supervised learning|semi-supervised]] or [[Unsupervised learning|unsupervised]].<ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="NatureBengio">{{cite journal |last1=Bengio |first1=Yoshua |last2=LeCun |first2= Yann| last3=Hinton | first3= Geoffrey|year=2015 |title=Deep Learning |journal=Nature |volume=521 |issue=7553 |pages=436–444 |doi=10.1038/nature14539 |pmid=26017442|bibcode=2015Natur.521..436L |url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256 }}</ref> +[http://204.152.217.73/ Domino99 Indonesia] -Deep learning architectures such as [[#Deep_neural_networks|deep neural network]]s, [[deep belief network]]s, [[recurrent neural networks]] and [[convolutional neural networks]] have been applied to fields including [[computer vision]], [[automatic speech recognition|speech recognition]], [[natural language processing]], [[audio recognition]], social network filtering, [[machine translation]], [[bioinformatics]], [[drug design]], medical image analysis, material inspection and [[board game]] programs, where they have produced results comparable to and in some cases surpassing human expert performance.<ref name=":9">{{Cite book |doi=10.1109/cvpr.2012.6248110 |isbn=978-1-4673-1228-8|arxiv=1202.2745|chapter=Multi-column deep neural networks for image classification|title=2012 IEEE Conference on Computer Vision and Pattern Recognition|pages=3642–3649|year=2012|last1=Ciresan|first1=D.|last2=Meier|first2=U.|last3=Schmidhuber|first3=J.}}</ref><ref name="krizhevsky2012">{{cite journal|last1=Krizhevsky|first1=Alex|last2=Sutskever|first2=Ilya|last3=Hinton|first3=Geoffry|date=2012|title=ImageNet Classification with Deep Convolutional Neural Networks|url=https://www.cs.toronto.edu/~kriz/imagenet_classification_with_deep_convolutional.pdf|journal=NIPS 2012: Neural Information Processing Systems, Lake Tahoe, Nevada}} -</ref><ref>{{cite web |title=Google's AlphaGo AI wins three-match series against the world's best Go player |url=https://techcrunch.com/2017/05/24/alphago-beats-planets-best-human-go-player-ke-jie/amp/ |website=TechCrunch |date=25 May 2017}}</ref> +[http://204.152.217.73/ Bandar DominoQQ] -[[Artificial neural network]]s (ANNs) were inspired by information processing and distributed communication nodes in biological systems. ANNs have various differences from biological [[brain]]s. Specifically, neural networks tend to be static and symbolic, while the biological brain of most living organisms is dynamic (plastic) and analog.<ref>{{Cite journal|last=Marblestone|first=Adam H.|last2=Wayne|first2=Greg|last3=Kording|first3=Konrad P.|date=2016|title=Toward an Integration of Deep Learning and Neuroscience |journal=Frontiers in Computational Neuroscience |volume=10|pages=94|doi=10.3389/fncom.2016.00094 |pmc=5021692|pmid=27683554|bibcode=2016arXiv160603813M|arxiv=1606.03813|url=https://www.semanticscholar.org/paper/2dec4f52b1ce552b416f086d4ea1040626675dfa}}</ref><ref>{{cite journal|last1=Olshausen|first1=B. A.|year=1996|title=Emergence of simple-cell receptive field properties by learning a sparse code for natural images|journal=Nature|volume=381|issue=6583|pages=607–609|bibcode=1996Natur.381..607O|doi=10.1038/381607a0|pmid=8637596|url=https://www.semanticscholar.org/paper/8012c4a1e2ca663f1a04e80cbb19631a00cbab27}}</ref><ref>{{cite arxiv|last=Bengio|first=Yoshua|last2=Lee|first2=Dong-Hyun|last3=Bornschein|first3=Jorg|last4=Mesnard|first4=Thomas|last5=Lin|first5=Zhouhan|date=2015-02-13|title=Towards Biologically Plausible Deep Learning|eprint=1502.04156|class=cs.LG}}</ref> -{{toclimit|3}} - -== Definition == -[[File:Deep Learning.jpg|alt=Representing Images on Multiple Layers of Abstraction in Deep Learning|thumb|Representing Images on Multiple Layers of Abstraction in Deep Learning <ref>{{Cite journal|last=Schulz|first=Hannes|last2=Behnke|first2=Sven|date=2012-11-01|title=Deep Learning|journal=KI - Künstliche Intelligenz|language=en|volume=26|issue=4|pages=357–363|doi=10.1007/s13218-012-0198-z|issn=1610-1987|url=https://www.semanticscholar.org/paper/51a80649d16a38d41dbd20472deb3bc9b61b59a0}}</ref>]] -Deep learning is a class of [[machine learning]] [[algorithm]]s that<ref name="BOOK2014">{{cite journal|last2=Yu|first2=D.|year=2014|title=Deep Learning: Methods and Applications|url=http://research.microsoft.com/pubs/209355/DeepLearning-NowPublishing-Vol7-SIG-039.pdf|journal=Foundations and Trends in Signal Processing|volume=7|issue=3–4|pages=1–199|doi=10.1561/2000000039|last1=Deng|first1=L.}}</ref>{{rp|pages=199–200}} uses multiple layers to progressively extract higher level features from the raw input. For example, in [[image processing]], lower layers may identify edges, while higher layers may identify the concepts relevant to a human such as digits or letters or faces. - -== Overview == -Most modern deep learning models are based on artificial neural networks, specifically, [[Convolutional Neural Network]]s (CNN)s, although they can also include [[propositional formula]]s or latent variables organized layer-wise in deep [[generative model]]s such as the nodes in [[deep belief network]]s and deep [[Boltzmann machine]]s.<ref name="BENGIODEEP">{{cite journal|last=Bengio|first=Yoshua|year=2009|title=Learning Deep Architectures for AI|url=http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20%282009%29.pdf|journal=Foundations and Trends in Machine Learning|volume=2|issue=1|pages=1–127|doi=10.1561/2200000006|citeseerx=10.1.1.701.9550|access-date=2015-09-03|archive-url=https://web.archive.org/web/20160304084250/http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20(2009).pdf|archive-date=2016-03-04|url-status=dead}}</ref> - -In deep learning, each level learns to transform its input data into a slightly more abstract and composite representation. In an image recognition application, the raw input may be a [[Matrix (mathematics)|matrix]] of pixels; the first representational layer may abstract the pixels and encode edges; the second layer may compose and encode arrangements of edges; the third layer may encode a nose and eyes; and the fourth layer may recognize that the image contains a face. Importantly, a deep learning process can learn which features to optimally place in which level ''on its own''. (Of course, this does not completely eliminate the need for hand-tuning; for example, varying numbers of layers and layer sizes can provide different degrees of abstraction.)<ref name="BENGIO2012">{{cite journal|last2=Courville|first2=A.|last3=Vincent|first3=P.|year=2013|title=Representation Learning: A Review and New Perspectives|journal=IEEE Transactions on Pattern Analysis and Machine Intelligence|volume=35|issue=8|pages=1798–1828|arxiv=1206.5538|doi=10.1109/tpami.2013.50|pmid=23787338|last1=Bengio|first1=Y.}}</ref><ref>{{cite journal|last1=LeCun|first1=Yann|last2=Bengio|first2=Yoshua|last3=Hinton|first3=Geoffrey|title=Deep learning|journal=Nature|date=28 May 2015|volume=521|issue=7553|pages=436–444|doi=10.1038/nature14539|pmid=26017442|bibcode=2015Natur.521..436L|url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256}}</ref> - -The word "deep" in "deep learning" refers to the number of layers through which the data is transformed. More precisely, deep learning systems have a substantial ''credit assignment path'' (CAP) depth. The CAP is the chain of transformations from input to output. CAPs describe potentially causal connections between input and output. For a [[feedforward neural network]], the depth of the CAPs is that of the network and is the number of hidden layers plus one (as the output layer is also parameterized). For [[recurrent neural network]]s, in which a signal may propagate through a layer more than once, the CAP depth is potentially unlimited.<ref name="SCHIDHUB" /> No universally agreed upon threshold of depth divides shallow learning from deep learning, but most researchers agree that deep learning involves CAP depth higher than 2. CAP of depth 2 has been shown to be a universal approximator in the sense that it can emulate any function.<ref>{{Cite book|url=https://books.google.com/books?id=9CqQDwAAQBAJ&pg=PA15&dq#v=onepage&q&f=false|title=Human Behavior and Another Kind in Consciousness: Emerging Research and Opportunities: Emerging Research and Opportunities|last=Shigeki|first=Sugiyama|date=2019-04-12|publisher=IGI Global|isbn=978-1-5225-8218-2|language=en}}</ref> Beyond that, more layers do not add to the function approximator ability of the network. Deep models (CAP > 2) are able to extract better features than shallow models and hence, extra layers help in learning the features effectively. - -Deep learning architectures can be constructed with a [[greedy algorithm|greedy]] layer-by-layer method.<ref name=BENGIO2007>{{cite conference | first1=Yoshua | last1=Bengio | first2=Pascal | last2=Lamblin | first3=Dan|last3=Popovici |first4=Hugo|last4=Larochelle | title=Greedy layer-wise training of deep networks| year=2007 | url=http://papers.nips.cc/paper/3048-greedy-layer-wise-training-of-deep-networks.pdf| conference = Advances in neural information processing systems | pages= 153–160}}</ref> Deep learning helps to disentangle these abstractions and pick out which features improve performance.<ref name="BENGIO2012" /> - -For [[supervised learning]] tasks, deep learning methods eliminate [[feature engineering]], by translating the data into compact intermediate representations akin to [[Principal Component Analysis|principal components]], and derive layered structures that remove redundancy in representation. - -Deep learning algorithms can be applied to unsupervised learning tasks. This is an important benefit because unlabeled data are more abundant than the labeled data. Examples of deep structures that can be trained in an unsupervised manner are neural history compressors<ref name="scholarpedia">Jürgen Schmidhuber (2015). Deep Learning. Scholarpedia, 10(11):32832. [http://www.scholarpedia.org/article/Deep_Learning Online]</ref> and [[deep belief network]]s.<ref name="BENGIO2012" /><ref name="SCHOLARDBNS">{{cite journal | last1 = Hinton | first1 = G.E. | year = 2009| title = Deep belief networks | url= | journal = Scholarpedia | volume = 4 | issue = 5| page = 5947 | doi=10.4249/scholarpedia.5947| bibcode = 2009SchpJ...4.5947H}}</ref> - -== Interpretations == -Deep neural networks are generally interpreted in terms of the [[universal approximation theorem]]<ref name="ReferenceB">Balázs Csanád Csáji (2001). Approximation with Artificial Neural Networks; Faculty of Sciences; Eötvös Loránd University, Hungary</ref><ref name=cyb>{{cite journal | last1 = Cybenko | year = 1989 | title = Approximations by superpositions of sigmoidal functions | url = http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | journal = [[Mathematics of Control, Signals, and Systems]] | volume = 2 | issue = 4 | pages = 303–314 | doi = 10.1007/bf02551274 | url-status = dead | archiveurl = https://web.archive.org/web/20151010204407/http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | archivedate = 2015-10-10 }}</ref><ref name=horn>{{cite journal | last1 = Hornik | first1 = Kurt | year = 1991 | title = Approximation Capabilities of Multilayer Feedforward Networks | url= | journal = Neural Networks | volume = 4 | issue = 2| pages = 251–257 | doi=10.1016/0893-6080(91)90009-t}}</ref><ref name="Haykin, Simon 1998">{{cite book|first=Simon S. |last=Haykin|title=Neural Networks: A Comprehensive Foundation|url={{google books |plainurl=y |id=bX4pAQAAMAAJ}}|year=1999|publisher=Prentice Hall|isbn=978-0-13-273350-2}}</ref><ref name="Hassoun, M. 1995 p. 48">{{cite book|first=Mohamad H. |last=Hassoun|title=Fundamentals of Artificial Neural Networks|url={{google books |plainurl=y |id=Otk32Y3QkxQC|page=48}}|year=1995|publisher=MIT Press|isbn=978-0-262-08239-6|p=48}}</ref><ref name=ZhouLu>Lu, Z., Pu, H., Wang, F., Hu, Z., & Wang, L. (2017). [http://papers.nips.cc/paper/7203-the-expressive-power-of-neural-networks-a-view-from-the-width The Expressive Power of Neural Networks: A View from the Width]. Neural Information Processing Systems, 6231-6239. -</ref> or [[Bayesian inference|probabilistic inference]].<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB">{{cite journal|last=Schmidhuber|first=J.|year=2015|title=Deep Learning in Neural Networks: An Overview|journal=Neural Networks|volume=61|pages=85–117|arxiv=1404.7828|doi=10.1016/j.neunet.2014.09.003|pmid=25462637|url=https://www.semanticscholar.org/paper/126df9f24e29feee6e49e135da102fbbd9154a48}}</ref><ref name="SCHOLARDBNS" /><ref name = MURPHY>{{cite book|first=Kevin P. |last=Murphy|title=Machine Learning: A Probabilistic Perspective|url={{google books |plainurl=y |id=NZP6AQAAQBAJ}}|date=24 August 2012|publisher=MIT Press|isbn=978-0-262-01802-9}}</ref><ref name= "Patel NIPS 2016">{{Cite journal|url=https://papers.nips.cc/paper/6231-a-probabilistic-framework-for-deep-learning.pdf|title=A Probabilistic Framework for Deep Learning|last=Patel|first=Ankit|last2=Nguyen|first2=Tan|last3=Baraniuk|first3=Richard|date=2016|journal=Advances in Neural Information Processing Systems|pages=|bibcode=2016arXiv161201936P|arxiv=1612.01936}}</ref> - -The classic universal approximation theorem concerns the capacity of [[feedforward neural networks]] with a single hidden layer of finite size to approximate [[continuous functions]].<ref name="ReferenceB"/><ref name="cyb"/><ref name="horn"/><ref name="Haykin, Simon 1998"/><ref name="Hassoun, M. 1995 p. 48"/> In 1989, the first proof was published by [[George Cybenko]] for [[sigmoid function|sigmoid]] activation functions<ref name="cyb" /> and was generalised to feed-forward multi-layer architectures in 1991 by Kurt Hornik.<ref name="horn" /> Recent work also showed that universal approximation also holds for non-bounded activation functions such as the rectified linear unit.<ref name=sonoda17>{{cite journal | last1 = Sonoda | first1 = Sho | last2=Murata | first2=Noboru | year = 2017 | title = Neural network with unbounded activation functions is universal approximator | journal = Applied and Computational Harmonic Analysis | volume = 43 | issue = 2 | pages = 233–268 | doi = 10.1016/j.acha.2015.12.005| arxiv = 1505.03654 | url = https://www.semanticscholar.org/paper/d0e48a4d5d6d0b4aa2dbab2c50560945e62a3817 }}</ref> - -The universal approximation theorem for [[deep neural network]]s concerns the capacity of networks with bounded width but the depth is allowed to grow. Lu et al.<ref name=ZhouLu/> proved that if the width of a [[deep neural network]] with [[ReLU]] activation is strictly larger than the input dimension, then the network can approximate any [[Lebesgue integration|Lebesgue integrable function]]; If the width is smaller or equal to the input dimension, then [[deep neural network]] is not a universal approximator. - -The [[probabilistic]] interpretation<ref name="MURPHY" /> derives from the field of [[machine learning]]. It features inference,<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="SCHOLARDBNS" /><ref name="MURPHY" /> as well as the [[optimization]] concepts of [[training]] and [[test (assessment)|testing]], related to fitting and [[generalization]], respectively. More specifically, the probabilistic interpretation considers the activation nonlinearity as a [[cumulative distribution function]].<ref name="MURPHY" /> The probabilistic interpretation led to the introduction of [[dropout (neural networks)|dropout]] as [[Regularization (mathematics)|regularizer]] in neural networks.<ref name="DROPOUT">{{cite arXiv |last1=Hinton |first1=G. E. |last2=Srivastava| first2 =N.|last3=Krizhevsky| first3=A.| last4 =Sutskever| first4=I.| last5=Salakhutdinov| first5=R.R.|eprint=1207.0580 |class=math.LG |title=Improving neural networks by preventing co-adaptation of feature detectors |date=2012}}</ref> The probabilistic interpretation was introduced by researchers including [[John Hopfield|Hopfield]], [[Bernard Widrow|Widrow]] and [[Kumpati S. Narendra|Narendra]] and popularized in surveys such as the one by [[Christopher Bishop|Bishop]].<ref name="prml">{{cite book|title=Pattern Recognition and Machine Learning|author=Bishop, Christopher M.|year=2006|publisher=Springer|url=http://users.isr.ist.utl.pt/~wurmd/Livros/school/Bishop%20-%20Pattern%20Recognition%20And%20Machine%20Learning%20-%20Springer%20%202006.pdf|isbn=978-0-387-31073-2}}</ref> - -== History == -The term ''Deep Learning'' was introduced to the machine learning community by [[Rina Dechter]] in 1986,<ref name="dechter1986">[[Rina Dechter]] (1986). Learning while searching in constraint-satisfaction problems. University of California, Computer Science Department, Cognitive Systems Laboratory.[https://www.researchgate.net/publication/221605378_Learning_While_Searching_in_Constraint-Satisfaction-Problems Online]</ref><ref name="scholarpedia" /> and to [[Artificial Neural Networks|artificial neural networks]] by Igor Aizenberg and colleagues in 2000, in the context of [[Boolean network|Boolean]] threshold neurons.<ref name="aizenberg2000">Igor Aizenberg, Naum N. Aizenberg, Joos P.L. Vandewalle (2000). Multi-Valued and Universal Binary Neurons: Theory, Learning and Applications. Springer Science & Business Media.</ref><ref>Co-evolving recurrent neurons learn deep memory POMDPs. Proc. GECCO, Washington, D. C., pp. 1795-1802, ACM Press, New York, NY, USA, 2005.</ref> - -The first general, working learning algorithm for supervised, deep, feedforward, multilayer [[perceptron]]s was published by [[Alexey Ivakhnenko]] and Lapa in 1967.<ref name="ivak1965">{{cite book|first1=A. G. |last1=Ivakhnenko |first2=V. G. |last2=Lapa |title=Cybernetics and Forecasting Techniques|url={{google books |plainurl=y |id=rGFgAAAAMAAJ}}|year=1967|publisher=American Elsevier Publishing Co.|isbn=978-0-444-00020-0}}</ref> A 1971 paper described already a deep network with 8 layers trained by the [[group method of data handling]] algorithm.<ref name="ivak1971">{{Cite journal|last=Ivakhnenko|first=Alexey|date=1971|title=Polynomial theory of complex systems|url=http://gmdh.net/articles/history/polynomial.pdf |journal=IEEE Transactions on Systems, Man and Cybernetics |pages=364–378|doi=10.1109/TSMC.1971.4308320|pmid=|accessdate=|volume=SMC-1|issue=4}}</ref> - -Other deep learning working architectures, specifically those built for [[computer vision]], began with the [[Neocognitron]] introduced by [[Kunihiko Fukushima]] in 1980.<ref name="FUKU1980">{{cite journal | last1 = Fukushima | first1 = K. | year = 1980 | title = Neocognitron: A self-organizing neural network model for a mechanism of pattern recognition unaffected by shift in position | url= | journal = Biol. Cybern. | volume = 36 | issue = 4| pages = 193–202 | doi=10.1007/bf00344251 | pmid=7370364}}</ref> In 1989, [[Yann LeCun]] et al. applied the standard backpropagation algorithm, which had been around as the reverse mode of [[automatic differentiation]] since 1970,<ref name="lin1970">[[Seppo Linnainmaa]] (1970). The representation of the cumulative rounding error of an algorithm as a Taylor expansion of the local rounding errors. Master's Thesis (in Finnish), Univ. Helsinki, 6-7.</ref><ref name="grie2012">{{Cite journal|last=Griewank|first=Andreas|date=2012|title=Who Invented the Reverse Mode of Differentiation?|url=http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|journal=Documenta Mathematica|issue=Extra Volume ISMP|pages=389–400|access-date=2017-06-11|archive-url=https://web.archive.org/web/20170721211929/http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|archive-date=2017-07-21|url-status=dead}}</ref><ref name="WERBOS1974">{{Cite journal|last=Werbos|first=P.|date=1974|title=Beyond Regression: New Tools for Prediction and Analysis in the Behavioral Sciences |url=https://www.researchgate.net/publication/35657389 |journal=Harvard University |accessdate=12 June 2017}}</ref><ref name="werbos1982">{{Cite book|chapter-url=ftp://ftp.idsia.ch/pub/juergen/habilitation.pdf|title=System modeling and optimization|last=Werbos|first=Paul|publisher=Springer|year=1982|isbn=|location=|pages=762–770|chapter=Applications of advances in nonlinear sensitivity analysis}}</ref> to a deep neural network with the purpose of recognizing handwritten [[ZIP code]]s on mail. While the algorithm worked, training required 3 days.<ref name="LECUN1989">LeCun ''et al.'', "Backpropagation Applied to Handwritten Zip Code Recognition," ''Neural Computation'', 1, pp. 541–551, 1989.</ref> - -By 1991 such systems were used for recognizing isolated 2-D hand-written digits, while [[3D object recognition|recognizing 3-D objects]] was done by matching 2-D images with a handcrafted 3-D object model. Weng ''et al.'' suggested that a human brain does not use a monolithic 3-D object model and in 1992 they published Cresceptron,<ref name="Weng1992">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCNN1992.pdf Cresceptron: a self-organizing neural network which grows adaptively]," ''Proc. International Joint Conference on Neural Networks'', Baltimore, Maryland, vol I, pp. 576-581, June, 1992.</ref><ref name="Weng1993">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronICCV1993.pdf Learning recognition and segmentation of 3-D objects from 2-D images]," ''Proc. 4th International Conf. Computer Vision'', Berlin, Germany, pp. 121-128, May, 1993.</ref><ref name="Weng1997">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCV.pdf Learning recognition and segmentation using the Cresceptron]," ''International Journal of Computer Vision'', vol. 25, no. 2, pp. 105-139, Nov. 1997.</ref> a method for performing 3-D object recognition in cluttered scenes. Because it directly used natural images, Cresceptron started the beginning of general-purpose visual learning for natural 3D worlds. Cresceptron is a cascade of layers similar to Neocognitron. But while Neocognitron required a human programmer to hand-merge features, Cresceptron learned an open number of features in each layer without supervision, where each feature is represented by a [[Convolution|convolution kernel]]. Cresceptron segmented each learned object from a cluttered scene through back-analysis through the network. [[Max pooling]], now often adopted by deep neural networks (e.g. [[ImageNet]] tests), was first used in Cresceptron to reduce the position resolution by a factor of (2x2) to 1 through the cascade for better generalization. - -In 1994, André de Carvalho, together with Mike Fairhurst and David Bisset, published experimental results of a multi-layer boolean neural network, also known as a weightless neural network, composed of a 3-layers self-organising feature extraction neural network module (SOFT) followed by a multi-layer classification neural network module (GSN), which were independently trained. Each layer in the feature extraction module extracted features with growing complexity regarding the previous layer.<ref>{{Cite journal |title=An integrated Boolean neural network for pattern classification |journal=Pattern Recognition Letters |date=1994-08-08 |pages=807–813 |volume=15 |issue=8 |doi=10.1016/0167-8655(94)90009-4 |first=Andre C. L. F. |last1=de Carvalho |first2 = Mike C. |last2=Fairhurst |first3=David |last3 = Bisset}}</ref> - -In 1995, [[Brendan Frey]] demonstrated that it was possible to train (over two days) a network containing six fully connected layers and several hundred hidden units using the [[wake-sleep algorithm]], co-developed with [[Peter Dayan]] and [[Geoffrey Hinton|Hinton]].<ref>{{Cite journal|title = The wake-sleep algorithm for unsupervised neural networks |journal = Science|date = 1995-05-26|pages = 1158–1161|volume = 268|issue = 5214|doi = 10.1126/science.7761831|pmid = 7761831|first = Geoffrey E.|last = Hinton|first2 = Peter|last2 = Dayan|first3 = Brendan J.|last3 = Frey|first4 = Radford|last4 = Neal|bibcode = 1995Sci...268.1158H}}</ref> Many factors contribute to the slow speed, including the [[vanishing gradient problem]] analyzed in 1991 by [[Sepp Hochreiter]].<ref name="HOCH1991">S. Hochreiter., "[http://people.idsia.ch/~juergen/SeppHochreiter1991ThesisAdvisorSchmidhuber.pdf Untersuchungen zu dynamischen neuronalen Netzen]," ''Diploma thesis. Institut f. Informatik, Technische Univ. Munich. Advisor: J. Schmidhuber'', 1991.</ref><ref name="HOCH2001">{{cite book|chapter-url={{google books |plainurl=y |id=NWOcMVA64aAC}}|title=A Field Guide to Dynamical Recurrent Networks|last=Hochreiter|first=S.|display-authors=etal|date=15 January 2001|publisher=John Wiley & Sons|isbn=978-0-7803-5369-5|location=|pages=|chapter=Gradient flow in recurrent nets: the difficulty of learning long-term dependencies|editor-last2=Kremer|editor-first2=Stefan C.|editor-first1=John F.|editor-last1=Kolen}}</ref> - -Simpler models that use task-specific handcrafted features such as [[Gabor filter]]s and [[support vector machine]]s (SVMs) were a popular choice in the 1990s and 2000s, because of [[artificial neural network]]'s (ANN) computational cost and a lack of understanding of how the brain wires its biological networks. - -Both shallow and deep learning (e.g., recurrent nets) of ANNs have been explored for many years.<ref>{{Cite journal|last=Morgan|first=Nelson|last2=Bourlard |first2=Hervé |last3=Renals |first3=Steve |last4=Cohen |first4=Michael|last5=Franco |first5=Horacio |date=1993-08-01 |title=Hybrid neural network/hidden markov model systems for continuous speech recognition |journal=International Journal of Pattern Recognition and Artificial Intelligence|volume=07|issue=4|pages=899–916|doi=10.1142/s0218001493000455|issn=0218-0014}}</ref><ref name="Robinson1992">{{Cite journal|last=Robinson|first=T.|authorlink=Tony Robinson (speech recognition)|date=1992|title=A real-time recurrent error propagation network word recognition system|url=http://dl.acm.org/citation.cfm?id=1895720|journal=ICASSP|pages=617–620|via=|isbn=9780780305328|series=Icassp'92}}</ref><ref>{{Cite journal|last=Waibel|first=A.|last2=Hanazawa|first2=T.|last3=Hinton|first3=G.|last4=Shikano|first4=K.|last5=Lang|first5=K. J.|date=March 1989|title=Phoneme recognition using time-delay neural networks|journal=IEEE Transactions on Acoustics, Speech, and Signal Processing|volume=37|issue=3|pages=328–339|doi=10.1109/29.21701|issn=0096-3518|hdl=10338.dmlcz/135496|url=http://dml.cz/bitstream/handle/10338.dmlcz/135496/Kybernetika_38-2002-6_2.pdf}}</ref> These methods never outperformed non-uniform internal-handcrafting Gaussian [[mixture model]]/[[Hidden Markov model]] (GMM-HMM) technology based on generative models of speech trained discriminatively.<ref name="Baker2009">{{cite journal | last1 = Baker | first1 = J. | last2 = Deng | first2 = Li | last3 = Glass | first3 = Jim | last4 = Khudanpur | first4 = S. | last5 = Lee | first5 = C.-H. | last6 = Morgan | first6 = N. | last7 = O'Shaughnessy | first7 = D. | year = 2009 | title = Research Developments and Directions in Speech Recognition and Understanding, Part 1 | url= | journal = IEEE Signal Processing Magazine | volume = 26 | issue = 3| pages = 75–80 | doi=10.1109/msp.2009.932166| bibcode = 2009ISPM...26...75B }}</ref> Key difficulties have been analyzed, including gradient diminishing<ref name="HOCH1991" /> and weak temporal correlation structure in neural predictive models.<ref name="Bengio1991">{{Cite web|url=https://www.researchgate.net/publication/41229141|title=Artificial Neural Networks and their Application to Speech/Sequence Recognition|last=Bengio|first=Y.|date=1991|website=|publisher=McGill University Ph.D. thesis|accessdate=}}</ref><ref name="Deng1994">{{cite journal | last1 = Deng | first1 = L. | last2 = Hassanein | first2 = K. | last3 = Elmasry | first3 = M. | year = 1994 | title = Analysis of correlation structure for a neural predictive model with applications to speech recognition | url= | journal = Neural Networks | volume = 7 | issue = 2| pages = 331–339 | doi=10.1016/0893-6080(94)90027-2}}</ref> Additional difficulties were the lack of training data and limited computing power. - -Most [[speech recognition]] researchers moved away from neural nets to pursue generative modeling. An exception was at [[SRI International]] in the late 1990s. Funded by the US government's [[National Security Agency|NSA]] and [[DARPA]], SRI studied deep neural networks in speech and speaker recognition. The speaker recognition team led by [[Larry Heck]] reported significant success with deep neural networks in speech processing in the 1998 [[National Institute of Standards and Technology]] Speaker Recognition evaluation.<ref name="Doddington2000">{{cite journal | last1 = Doddington | first1 = G. | last2 = Przybocki | first2 = M. | last3 = Martin | first3 = A. | last4 = Reynolds | first4 = D. | year = 2000 | title = The NIST speaker recognition evaluation ± Overview, methodology, systems, results, perspective | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 225–254 | doi=10.1016/S0167-6393(99)00080-1}}</ref> The SRI deep neural network was then deployed in the Nuance Verifier, representing the first major industrial application of deep learning.<ref name="Heck2000">{{cite journal | last1 = Heck | first1 = L. | last2 = Konig | first2 = Y. | last3 = Sonmez | first3 = M. | last4 = Weintraub | first4 = M. | year = 2000 | title = Robustness to Telephone Handset Distortion in Speaker Recognition by Discriminative Feature Design | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 181–192 | doi=10.1016/s0167-6393(99)00077-1}}</ref> - -The principle of elevating "raw" features over hand-crafted optimization was first explored successfully in the architecture of deep autoencoder on the "raw" spectrogram or linear filter-bank features in the late 1990s,<ref name="Heck2000" /> showing its superiority over the Mel-Cepstral features that contain stages of fixed transformation from spectrograms. The raw features of speech, [[waveform]]s, later produced excellent larger-scale results.<ref>{{Cite web|url=https://www.researchgate.net/publication/266030526|title=Acoustic Modeling with Deep Neural Networks Using Raw Time Signal for LVCSR (PDF Download Available)|website=ResearchGate|accessdate=2017-06-14}}</ref> - -Many aspects of speech recognition were taken over by a deep learning method called [[long short-term memory]] (LSTM), a recurrent neural network published by Hochreiter and [[Jürgen Schmidhuber|Schmidhuber]] in 1997.<ref name=":0">{{Cite journal|last=Hochreiter|first=Sepp|last2=Schmidhuber|first2=Jürgen|date=1997-11-01|title=Long Short-Term Memory|journal=Neural Computation|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|issn=0899-7667|pmid=9377276|url=https://www.semanticscholar.org/paper/44d2abe2175df8153f465f6c39b68b76a0d40ab9}}</ref> LSTM RNNs avoid the vanishing gradient problem and can learn "Very Deep Learning" tasks<ref name="SCHIDHUB" /> that require memories of events that happened thousands of discrete time steps before, which is important for speech. In 2003, LSTM started to become competitive with traditional speech recognizers on certain tasks.<ref name="graves2003">{{Cite web|url=Ftp://ftp.idsia.ch/pub/juergen/bioadit2004.pdf|title=Biologically Plausible Speech Recognition with LSTM Neural Nets|last=Graves|first=Alex|last2=Eck|first2=Douglas|date=2003|website=1st Intl. Workshop on Biologically Inspired Approaches to Advanced Information Technology, Bio-ADIT 2004, Lausanne, Switzerland|pages=175–184|last3=Beringer|first3=Nicole|last4=Schmidhuber|first4=Jürgen}}</ref> Later it was combined with connectionist temporal classification (CTC)<ref name=":1">{{Cite journal|last=Graves|first=Alex|last2=Fernández|first2=Santiago|last3=Gomez|first3=Faustino|date=2006|title=Connectionist temporal classification: Labelling unsegmented sequence data with recurrent neural networks|journal=Proceedings of the International Conference on Machine Learning, ICML 2006|pages=369–376|citeseerx=10.1.1.75.6306}}</ref> in stacks of LSTM RNNs.<ref name="fernandez2007keyword">Santiago Fernandez, Alex Graves, and Jürgen Schmidhuber (2007). [https://mediatum.ub.tum.de/doc/1289941/file.pdf An application of recurrent neural networks to discriminative keyword spotting]. Proceedings of ICANN (2), pp. 220–229.</ref> In 2015, Google's speech recognition reportedly experienced a dramatic performance jump of 49% through CTC-trained LSTM, which they made available through [[Google Voice Search]].<ref name="sak2015">{{Cite web|url=http://googleresearch.blogspot.ch/2015/09/google-voice-search-faster-and-more.html|title=Google voice search: faster and more accurate|last=Sak|first=Haşim|last2=Senior|first2=Andrew|date=September 2015|website=|accessdate=|last3=Rao|first3=Kanishka|last4=Beaufays|first4=Françoise|last5=Schalkwyk|first5=Johan}}</ref> - -In 2006, publications by [[Geoffrey Hinton|Geoff Hinton]], [[Russ Salakhutdinov|Ruslan Salakhutdinov]], Osindero and [[Yee Whye Teh|Teh]]<ref>{{Cite journal|last=Hinton|first=Geoffrey E.|date=2007-10-01|title=Learning multiple layers of representation|url=http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(07)00217-3|journal=Trends in Cognitive Sciences|volume=11|issue=10|pages=428–434|doi=10.1016/j.tics.2007.09.004|issn=1364-6613|pmid=17921042}}</ref> -<ref name=hinton06>{{Cite journal | last1 = Hinton | first1 = G. E. |authorlink1=Geoff Hinton| last2 = Osindero | first2 = S. | last3 = Teh | first3 = Y. W. | doi = 10.1162/neco.2006.18.7.1527 | title = A Fast Learning Algorithm for Deep Belief Nets | journal = [[Neural Computation (journal)|Neural Computation]]| volume = 18 | issue = 7 | pages = 1527–1554 | year = 2006 | pmid = 16764513| pmc = | url = http://www.cs.toronto.edu/~hinton/absps/fastnc.pdf}}</ref><ref name=bengio2012>{{cite arXiv |last=Bengio |first=Yoshua |author-link=Yoshua Bengio |eprint=1206.5533 |title=Practical recommendations for gradient-based training of deep architectures |class=cs.LG|year=2012 }}</ref> showed how a many-layered [[feedforward neural network]] could be effectively pre-trained one layer at a time, treating each layer in turn as an unsupervised [[restricted Boltzmann machine]], then fine-tuning it using supervised [[backpropagation]].<ref name="HINTON2007">G. E. Hinton., "[http://www.csri.utoronto.ca/~hinton/absps/ticsdraft.pdf Learning multiple layers of representation]," ''Trends in Cognitive Sciences'', 11, pp. 428–434, 2007.</ref> The papers referred to ''learning'' for ''deep belief nets.'' - -Deep learning is part of state-of-the-art systems in various disciplines, particularly computer vision and [[automatic speech recognition]] (ASR). Results on commonly used evaluation sets such as [[TIMIT]] (ASR) and [[MNIST database|MNIST]] ([[image classification]]), as well as a range of large-vocabulary speech recognition tasks have steadily improved.<ref name="HintonDengYu2012" /><ref>{{cite journal|url=https://www.microsoft.com/en-us/research/publication/new-types-of-deep-neural-network-learning-for-speech-recognition-and-related-applications-an-overview/|title=New types of deep neural network learning for speech recognition and related applications: An overview|journal=Microsoft Research|first1=Li|last1=Deng|first2=Geoffrey|last2=Hinton|first3=Brian|last3=Kingsbury|date=1 May 2013|via=research.microsoft.com|citeseerx=10.1.1.368.1123}}</ref><ref>{{Cite book |doi=10.1109/icassp.2013.6639345|isbn=978-1-4799-0356-6|chapter=Recent advances in deep learning for speech research at Microsoft|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8604–8608|year=2013|last1=Deng|first1=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Michael|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|last10=Williams|first10=Jason|last11=Gong|first11=Yifan|last12=Acero|first12=Alex}}</ref> [[Convolutional neural network]]s (CNNs) were superseded for ASR by CTC<ref name=":1" /> for LSTM.<ref name=":0" /><ref name="sak2015" /><ref name="sak2014">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|title=Long Short-Term Memory recurrent neural network architectures for large scale acoustic modeling|last=Sak|first=Hasim|last2=Senior|first2=Andrew|date=2014|website=|accessdate=|last3=Beaufays|first3=Francoise|archive-url=https://web.archive.org/web/20180424203806/https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|archive-date=2018-04-24|url-status=dead}}</ref><ref name="liwu2015">{{cite arxiv |eprint=1410.4281|last1=Li|first1=Xiangang|title=Constructing Long Short-Term Memory based Deep Recurrent Neural Networks for Large Vocabulary Speech Recognition|last2=Wu|first2=Xihong|class=cs.CL|year=2014}}</ref><ref name="zen2015">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=Unidirectional Long Short-Term Memory Recurrent Neural Network with Recurrent Output Layer for Low-Latency Speech Synthesis|last=Zen|first=Heiga|last2=Sak|first2=Hasim|date=2015|website=Google.com|publisher=ICASSP|pages=4470–4474|accessdate=}}</ref><ref name="CNNspeech2013">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=A deep convolutional neural network using heterogeneous pooling for trading acoustic invariance with phonetic confusion|last=Deng|first=L.|last2=Abdel-Hamid|first2=O.|date=2013|website=Google.com|publisher=ICASSP|accessdate=|last3=Yu|first3=D.}}</ref><ref name=":2">{{Cite book |doi=10.1109/icassp.2013.6639347|isbn=978-1-4799-0356-6|chapter=Deep convolutional neural networks for LVCSR|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8614–8618|year=2013|last1=Sainath|first1=Tara N.|last2=Mohamed|first2=Abdel-Rahman|last3=Kingsbury|first3=Brian|last4=Ramabhadran|first4=Bhuvana}}</ref> but are more successful in computer vision. - -The impact of deep learning in industry began in the early 2000s, when CNNs already processed an estimated 10% to 20% of all the checks written in the US, according to Yann LeCun.<ref name="lecun2016slides">[[Yann LeCun]] (2016). Slides on Deep Learning [https://indico.cern.ch/event/510372/ Online]</ref> Industrial applications of deep learning to large-scale speech recognition started around 2010. - -The 2009 NIPS Workshop on Deep Learning for Speech Recognition<ref name="NIPS2009" /> was motivated by the limitations of deep generative models of speech, and the possibility that given more capable hardware and large-scale data sets that deep neural nets (DNN) might become practical. It was believed that pre-training DNNs using generative models of deep belief nets (DBN) would overcome the main difficulties of neural nets.<ref name="HintonKeynoteICASSP2013" /> However, it was discovered that replacing pre-training with large amounts of training data for straightforward backpropagation when using DNNs with large, context-dependent output layers produced error rates dramatically lower than then-state-of-the-art Gaussian mixture model (GMM)/Hidden Markov Model (HMM) and also than more-advanced generative model-based systems.<ref name="HintonDengYu2012">{{cite journal | last1 = Hinton | first1 = G. | last2 = Deng | first2 = L. | last3 = Yu | first3 = D. | last4 = Dahl | first4 = G. | last5 = Mohamed | first5 = A. | last6 = Jaitly | first6 = N. | last7 = Senior | first7 = A. | last8 = Vanhoucke | first8 = V. | last9 = Nguyen | first9 = P. | last10 = Sainath | first10 = T. | last11 = Kingsbury | first11 = B. | year = 2012 | title = Deep Neural Networks for Acoustic Modeling in Speech Recognition: The Shared Views of Four Research Groups| url= | journal = IEEE Signal Processing Magazine | volume = 29 | issue = 6| pages = 82–97 | doi=10.1109/msp.2012.2205597}}</ref><ref name="patent2011">D. Yu, L. Deng, G. Li, and F. Seide (2011). "Discriminative pretraining of deep neural networks," U.S. Patent Filing.</ref> The nature of the recognition errors produced by the two types of systems was characteristically different,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009">NIPS Workshop: Deep Learning for Speech Recognition and Related Applications, Whistler, BC, Canada, Dec. 2009 (Organizers: Li Deng, Geoff Hinton, D. Yu).</ref> offering technical insights into how to integrate deep learning into the existing highly efficient, run-time speech decoding system deployed by all major speech recognition systems.<ref name="BOOK2014" /><ref name="ReferenceA">{{cite book|last2=Deng|first2=L.|date=2014|title=Automatic Speech Recognition: A Deep Learning Approach (Publisher: Springer)|url={{google books |plainurl=y |id=rUBTBQAAQBAJ}}|pages=|isbn=978-1-4471-5779-3|via=|last1=Yu|first1=D.}}</ref><ref>{{cite web|title=Deng receives prestigious IEEE Technical Achievement Award - Microsoft Research|url=https://www.microsoft.com/en-us/research/blog/deng-receives-prestigious-ieee-technical-achievement-award/|website=Microsoft Research|date=3 December 2015}}</ref> Analysis around 2009-2010, contrasted the GMM (and other generative speech models) vs. DNN models, stimulated early industrial investment in deep learning for speech recognition,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009" /> eventually leading to pervasive and dominant use in that industry. That analysis was done with comparable performance (less than 1.5% in error rate) between discriminative DNNs and generative models.<ref name="HintonDengYu2012" /><ref name="ReferenceICASSP2013">{{cite journal|last2=Hinton|first2=G.|last3=Kingsbury|first3=B.|date=2013|title=New types of deep neural network learning for speech recognition and related applications: An overview (ICASSP)|url=https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/ICASSP-2013-DengHintonKingsbury-revised.pdf|journal=|pages=|via=|last1=Deng|first1=L.}}</ref><ref name="HintonKeynoteICASSP2013">Keynote talk: Recent Developments in Deep Neural Networks. ICASSP, 2013 (by Geoff Hinton).</ref><ref name="interspeech2014Keynote">{{Cite web|url=https://www.superlectures.com/interspeech2014/downloadFile?id=6&type=slides&filename=achievements-and-challenges-of-deep-learning-from-speech-analysis-and-recognition-to-language-and-multimodal-processing|title=Keynote talk: 'Achievements and Challenges of Deep Learning - From Speech Analysis and Recognition To Language and Multimodal Processing'|last=Li|first=Deng|date=September 2014|website=Interspeech|accessdate=}}</ref> - -In 2010, researchers extended deep learning from TIMIT to large vocabulary speech recognition, by adopting large output layers of the DNN based on context-dependent HMM states constructed by [[decision tree]]s.<ref name="Roles2010">{{cite journal|last1=Yu|first1=D.|last2=Deng|first2=L.|date=2010|title=Roles of Pre-Training and Fine-Tuning in Context-Dependent DBN-HMMs for Real-World Speech Recognition|url=https://www.microsoft.com/en-us/research/publication/roles-of-pre-training-and-fine-tuning-in-context-dependent-dbn-hmms-for-real-world-speech-recognition/|journal=NIPS Workshop on Deep Learning and Unsupervised Feature Learning|pages=|via=}}</ref><ref>{{Cite journal|last=Seide|first=F.|last2=Li|first2=G.|last3=Yu|first3=D.|date=2011|title=Conversational speech transcription using context-dependent deep neural networks|url=https://www.microsoft.com/en-us/research/publication/conversational-speech-transcription-using-context-dependent-deep-neural-networks|journal=Interspeech|pages=|via=}}</ref><ref>{{Cite journal|last=Deng|first=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Mike|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|date=2013-05-01|title=Recent Advances in Deep Learning for Speech Research at Microsoft|url=https://www.microsoft.com/en-us/research/publication/recent-advances-in-deep-learning-for-speech-research-at-microsoft/|journal=Microsoft Research}}</ref><ref name="ReferenceA" /> - -Advances in hardware have enabled renewed interest in deep learning. In 2009, [[Nvidia]] was involved in what was called the “big bang” of deep learning, “as deep-learning neural networks were trained with Nvidia [[graphics processing unit]]s (GPUs).”<ref>{{cite web|url=https://venturebeat.com/2016/04/05/nvidia-ceo-bets-big-on-deep-learning-and-vr/|title=Nvidia CEO bets big on deep learning and VR|date=April 5, 2016|publisher=[[Venture Beat]]}}</ref> That year, [[Google Brain]] used Nvidia GPUs to create capable DNNs. While there, [[Andrew Ng]] determined that GPUs could increase the speed of deep-learning systems by about 100 times.<ref>{{cite news|url=https://www.economist.com/news/special-report/21700756-artificial-intelligence-boom-based-old-idea-modern-twist-not|title=From not working to neural networking|newspaper=[[The Economist]]}}</ref> In particular, GPUs are well-suited for the matrix/vector computations involved in machine learning.<ref name="jung2004">{{cite journal | last1 = Oh | first1 = K.-S. | last2 = Jung | first2 = K. | year = 2004 | title = GPU implementation of neural networks | url= | journal = Pattern Recognition | volume = 37 | issue = 6| pages = 1311–1314 | doi=10.1016/j.patcog.2004.01.013}}</ref><ref>"[https://www.academia.edu/40135801 A Survey of Techniques for Optimizing Deep Learning on GPUs]", S. Mittal and S. Vaishay, Journal of Systems Architecture, 2019</ref><ref name="chellapilla2006">Chellapilla, K., Puri, S., and Simard, P. (2006). High performance convolutional neural networks for document processing. International Workshop on Frontiers in Handwriting Recognition.</ref> GPUs speed up training algorithms by orders of magnitude, reducing running times from weeks to days.<ref name=":3">{{Cite journal|last=Cireşan|first=Dan Claudiu|last2=Meier|first2=Ueli|last3=Gambardella|first3=Luca Maria|last4=Schmidhuber|first4=Jürgen|date=2010-09-21|title=Deep, Big, Simple Neural Nets for Handwritten Digit Recognition|journal=Neural Computation|volume=22|issue=12|pages=3207–3220|doi=10.1162/neco_a_00052|pmid=20858131|issn=0899-7667|arxiv=1003.0358}}</ref><ref>{{Cite journal|last=Raina|first=Rajat|last2=Madhavan|first2=Anand|last3=Ng|first3=Andrew Y.|date=2009|title=Large-scale Deep Unsupervised Learning Using Graphics Processors|journal=Proceedings of the 26th Annual International Conference on Machine Learning|series=ICML '09|location=New York, NY, USA|publisher=ACM|pages=873–880|doi=10.1145/1553374.1553486|isbn=9781605585161|citeseerx=10.1.1.154.372|url=https://www.semanticscholar.org/paper/e337c5e4c23999c36f64bcb33ebe6b284e1bcbf1}}</ref> Further, specialized hardware and algorithm optimizations can be used for efficient processing of deep learning models.<ref name="sze2017">{{cite arXiv -|title= Efficient Processing of Deep Neural Networks: A Tutorial and Survey -|last1=Sze |first1=Vivienne -|last2=Chen |first2=Yu-Hsin -|last3=Yang |first3=Tien-Ju -|last4=Emer |first4=Joel -|eprint=1703.09039 -|year=2017 -|class=cs.CV }}</ref> - -=== Deep learning revolution === -[[File:AI-ML-DL.png|thumb|How deep learning is a subset of machine learning and how machine learning is a subset of artificial intelligence (AI).]] -In 2012, a team led by George E. Dahl won the "Merck Molecular Activity Challenge" using multi-task deep neural networks to predict the [[biomolecular target]] of one drug.<ref name="MERCK2012">{{cite web|url=https://www.kaggle.com/c/MerckActivity/details/winners|title=Announcement of the winners of the Merck Molecular Activity Challenge}}</ref><ref name=":5">{{Cite web|url=http://www.datascienceassn.org/content/multi-task-neural-networks-qsar-predictions|title=Multi-task Neural Networks for QSAR Predictions {{!}} Data Science Association|website=www.datascienceassn.org|accessdate=2017-06-14}}</ref> In 2014, Hochreiter's group used deep learning to detect off-target and toxic effects of environmental chemicals in nutrients, household products and drugs and won the "Tox21 Data Challenge" of [[NIH]], [[FDA]] and [[National Center for Advancing Translational Sciences|NCATS]].<ref name="TOX21">"Toxicology in the 21st century Data Challenge"</ref><ref name="TOX21Data">{{cite web|url=https://tripod.nih.gov/tox21/challenge/leaderboard.jsp|title=NCATS Announces Tox21 Data Challenge Winners}}</ref><ref name=":11">{{cite web|url=http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|title=Archived copy|archiveurl=https://web.archive.org/web/20150228225709/http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|archivedate=2015-02-28|url-status=dead|accessdate=2015-03-05}}</ref> - -Significant additional impacts in image or object recognition were felt from 2011 to 2012. Although CNNs trained by backpropagation had been around for decades, and GPU implementations of NNs for years, including CNNs, fast implementations of CNNs with max-pooling on GPUs in the style of Ciresan and colleagues were needed to progress on computer vision.<ref name="jung2004" /><ref name="chellapilla2006" /><ref name="LECUN1989" /><ref name=":6">{{Cite journal|last=Ciresan|first=D. C.|last2=Meier|first2=U.|last3=Masci|first3=J.|last4=Gambardella|first4=L. M.|last5=Schmidhuber|first5=J.|date=2011|title=Flexible, High Performance Convolutional Neural Networks for Image Classification|url=http://ijcai.org/papers11/Papers/IJCAI11-210.pdf|journal=International Joint Conference on Artificial Intelligence|pages=|doi=10.5591/978-1-57735-516-8/ijcai11-210|via=}}</ref><ref name="SCHIDHUB" /> In 2011, this approach achieved for the first time superhuman performance in a visual pattern recognition contest. Also in 2011, it won the ICDAR Chinese handwriting contest, and in May 2012, it won the ISBI image segmentation contest.<ref name=":8">{{Cite book|url=http://papers.nips.cc/paper/4741-deep-neural-networks-segment-neuronal-membranes-in-electron-microscopy-images.pdf|title=Advances in Neural Information Processing Systems 25|last=Ciresan|first=Dan|last2=Giusti|first2=Alessandro|last3=Gambardella|first3=Luca M.|last4=Schmidhuber|first4=Juergen|date=2012|publisher=Curran Associates, Inc.|editor-last=Pereira|editor-first=F.|pages=2843–2851|editor-last2=Burges|editor-first2=C. J. C.|editor-last3=Bottou|editor-first3=L.|editor-last4=Weinberger|editor-first4=K. Q.}}</ref> Until 2011, CNNs did not play a major role at computer vision conferences, but in June 2012, a paper by Ciresan et al. at the leading conference CVPR<ref name=":9" /> showed how max-pooling CNNs on GPU can dramatically improve many vision benchmark records. In October 2012, a similar system by Krizhevsky et al.<ref name="krizhevsky2012" /> won the large-scale [[ImageNet competition]] by a significant margin over shallow machine learning methods. In November 2012, Ciresan et al.'s system also won the ICPR contest on analysis of large medical images for cancer detection, and in the following year also the MICCAI Grand Challenge on the same topic.<ref name="ciresan2013miccai">{{Cite journal|last=Ciresan|first=D.|last2=Giusti|first2=A.|last3=Gambardella|first3=L.M.|last4=Schmidhuber|first4=J.|date=2013|title=Mitosis Detection in Breast Cancer Histology Images using Deep Neural Networks|journal=Proceedings MICCAI|volume=7908|issue=Pt 2|pages=411–418|doi=10.1007/978-3-642-40763-5_51|pmid=24579167|series=Lecture Notes in Computer Science|isbn=978-3-642-38708-1}}</ref> In 2013 and 2014, the error rate on the ImageNet task using deep learning was further reduced, following a similar trend in large-scale speech recognition. The [[Stephen Wolfram|Wolfram]] Image Identification project publicized these improvements.<ref>{{Cite web|url=https://www.imageidentify.com/|title=The Wolfram Language Image Identification Project|website=www.imageidentify.com|accessdate=2017-03-22}}</ref> - -Image classification was then extended to the more challenging task of [[Automatic image annotation|generating descriptions]] (captions) for images, often as a combination of CNNs and LSTMs.<ref name="1411.4555">{{cite arxiv |eprint=1411.4555|last1=Vinyals|first1=Oriol|title=Show and Tell: A Neural Image Caption Generator|last2=Toshev|first2=Alexander|last3=Bengio|first3=Samy|last4=Erhan|first4=Dumitru|class=cs.CV|year=2014}}.</ref><ref name="1411.4952">{{cite arxiv |eprint=1411.4952|last1=Fang|first1=Hao|title=From Captions to Visual Concepts and Back|last2=Gupta|first2=Saurabh|last3=Iandola|first3=Forrest|last4=Srivastava|first4=Rupesh|last5=Deng|first5=Li|last6=Dollár|first6=Piotr|last7=Gao|first7=Jianfeng|last8=He|first8=Xiaodong|last9=Mitchell|first9=Margaret|last10=Platt|first10=John C|last11=Lawrence Zitnick|first11=C|last12=Zweig|first12=Geoffrey|class=cs.CV|year=2014}}.</ref><ref name="1411.2539">{{cite arxiv |eprint=1411.2539|last1=Kiros|first1=Ryan|title=Unifying Visual-Semantic Embeddings with Multimodal Neural Language Models|last2=Salakhutdinov|first2=Ruslan|last3=Zemel|first3=Richard S|class=cs.LG|year=2014}}.</ref><ref>{{Cite journal|last=Zhong|first=Sheng-hua|last2=Liu|first2=Yan|last3=Liu|first3=Yang|date=2011|title=Bilinear Deep Learning for Image Classification|journal=Proceedings of the 19th ACM International Conference on Multimedia|series=MM '11|location=New York, NY, USA|publisher=ACM|pages=343–352|doi=10.1145/2072298.2072344|isbn=9781450306164|url=https://www.semanticscholar.org/paper/e1bbfb2c7ef74445b4fad9199b727464129df582}}</ref> - -Some researchers assess that the October 2012 ImageNet victory anchored the start of a "deep learning revolution" that has transformed the AI industry.<ref>{{cite news|title=Why Deep Learning Is Suddenly Changing Your Life|url=http://fortune.com/ai-artificial-intelligence-deep-machine-learning/|accessdate=13 April 2018|work=Fortune|date=2016}}</ref> - -In March 2019, [[Yoshua Bengio]], [[Geoffrey Hinton]] and [[Yann LeCun]] were awarded the [[Turing Award]] for conceptual and engineering breakthroughs that have made deep neural networks a critical component of computing. - -== Neural networks == - -=== Artificial neural networks === -{{Main|Artificial neural network}} -'''Artificial neural networks''' ('''ANNs''') or '''[[Connectionism|connectionist]] systems''' are computing systems inspired by the [[biological neural network]]s that constitute animal brains. Such systems learn (progressively improve their ability) to do tasks by considering examples, generally without task-specific programming. For example, in image recognition, they might learn to identify images that contain cats by analyzing example images that have been manually [[Labeled data|labeled]] as "cat" or "no cat" and using the analytic results to identify cats in other images. They have found most use in applications difficult to express with a traditional computer algorithm using [[rule-based programming]]. - -An ANN is based on a collection of connected units called [[artificial neuron]]s, (analogous to biological neurons in a [[Brain|biological brain]]). Each connection ([[synapse]]) between neurons can transmit a signal to another neuron. The receiving (postsynaptic) neuron can process the signal(s) and then signal downstream neurons connected to it. Neurons may have state, generally represented by [[real numbers]], typically between 0 and 1. Neurons and synapses may also have a weight that varies as learning proceeds, which can increase or decrease the strength of the signal that it sends downstream. - -Typically, neurons are organized in layers. Different layers may perform different kinds of transformations on their inputs. Signals travel from the first (input), to the last (output) layer, possibly after traversing the layers multiple times. - -The original goal of the neural network approach was to solve problems in the same way that a human brain would. Over time, attention focused on matching specific mental abilities, leading to deviations from biology such as backpropagation, or passing information in the reverse direction and adjusting the network to reflect that information. - -Neural networks have been used on a variety of tasks, including computer vision, [[speech recognition]], [[machine translation]], [[social network]] filtering, [[general game playing|playing board and video games]] and medical diagnosis. - -As of 2017, neural networks typically have a few thousand to a few million units and millions of connections. Despite this number being several order of magnitude less than the number of neurons on a human brain, these networks can perform many tasks at a level beyond that of humans (e.g., recognizing faces, playing "Go"<ref>{{Cite journal|last=Silver|first=David|last2=Huang|first2=Aja|last3=Maddison|first3=Chris J.|last4=Guez|first4=Arthur|last5=Sifre|first5=Laurent|last6=Driessche|first6=George van den|last7=Schrittwieser|first7=Julian|last8=Antonoglou|first8=Ioannis|last9=Panneershelvam|first9=Veda|date=January 2016|title=Mastering the game of Go with deep neural networks and tree search|journal=Nature|volume=529|issue=7587|pages=484–489|doi=10.1038/nature16961|issn=1476-4687|pmid=26819042|bibcode=2016Natur.529..484S|url=https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}</ref> ). - -=== Deep neural networks === -{{technical|section|date=July 2016}} -A deep neural network (DNN) is an [[artificial neural network]] (ANN) with multiple layers between the input and output layers.<ref name="BENGIODEEP" /><ref name="SCHIDHUB" /> The DNN finds the correct mathematical manipulation to turn the input into the output, whether it be a [[linear relationship]] or a non-linear relationship. The network moves through the layers calculating the probability of each output. For example, a DNN that is trained to recognize dog breeds will go over the given image and calculate the probability that the dog in the image is a certain breed. The user can review the results and select which probabilities the network should display (above a certain threshold, etc.) and return the proposed label. Each mathematical manipulation as such is considered a layer, and complex DNN have many layers, hence the name "deep" networks. - -DNNs can model complex non-linear relationships. DNN architectures generate compositional models where the object is expressed as a layered composition of [[Primitive data type|primitives]].<ref>{{Cite journal|last=Szegedy|first=Christian|last2=Toshev|first2=Alexander|last3=Erhan|first3=Dumitru|date=2013|title=Deep neural networks for object detection|url=https://papers.nips.cc/paper/5207-deep-neural-networks-for-object-detection|journal=Advances in Neural Information Processing Systems|pages=2553–2561|via=}}</ref> The extra layers enable composition of features from lower layers, potentially modeling complex data with fewer units than a similarly performing shallow network.<ref name="BENGIODEEP" /> - -Deep architectures include many variants of a few basic approaches. Each architecture has found success in specific domains. It is not always possible to compare the performance of multiple architectures, unless they have been evaluated on the same data sets. - -DNNs are typically feedforward networks in which data flows from the input layer to the output layer without looping back. At first, the DNN creates a map of virtual neurons and assigns random numerical values, or "weights", to connections between them. The weights and inputs are multiplied and return an output between 0 and 1. If the network did not accurately recognize a particular pattern, an algorithm would adjust the weights.<ref>{{Cite news|url=https://www.technologyreview.com/s/513696/deep-learning/|title=Is Artificial Intelligence Finally Coming into Its Own?|last=Hof|first=Robert D.|work=MIT Technology Review|access-date=2018-07-10}}</ref> That way the algorithm can make certain parameters more influential, until it determines the correct mathematical manipulation to fully process the data. - -[[Recurrent neural networks]] (RNNs), in which data can flow in any direction, are used for applications such as [[language model]]ing.<ref name="gers2001">{{cite journal|last1=Gers|first1=Felix A.|last2=Schmidhuber|first2=Jürgen|year=2001|title=LSTM Recurrent Networks Learn Simple Context Free and Context Sensitive Languages|url=http://elartu.tntu.edu.ua/handle/lib/30719|journal= IEEE Transactions on Neural Networks|volume=12|issue=6|pages=1333–1340|doi=10.1109/72.963769|pmid=18249962}}</ref><ref name="NIPS2014"/><ref name="vinyals2016">{{cite arxiv |eprint=1602.02410|last1=Jozefowicz|first1=Rafal|title=Exploring the Limits of Language Modeling|last2=Vinyals|first2=Oriol|last3=Schuster|first3=Mike|last4=Shazeer|first4=Noam|last5=Wu|first5=Yonghui|class=cs.CL|year=2016}}</ref><ref name="gillick2015">{{cite arxiv |eprint=1512.00103|last1=Gillick|first1=Dan|title=Multilingual Language Processing from Bytes|last2=Brunk|first2=Cliff|last3=Vinyals|first3=Oriol|last4=Subramanya|first4=Amarnag|class=cs.CL|year=2015}}</ref><ref name="MIKO2010">{{Cite journal|last=Mikolov|first=T.|display-authors=etal|date=2010|title=Recurrent neural network based language model|url=http://www.fit.vutbr.cz/research/groups/speech/servite/2010/rnnlm_mikolov.pdf|journal=Interspeech|pages=|via=}}</ref> Long short-term memory is particularly effective for this use.<ref name=":0" /><ref name=":10">{{Cite web|url=https://www.researchgate.net/publication/220320057|title=Learning Precise Timing with LSTM Recurrent Networks (PDF Download Available)|website=ResearchGate|accessdate=2017-06-13}}</ref> - -[[Convolutional neural network|Convolutional deep neural networks (CNNs)]] are used in computer vision.<ref name="LECUN86">{{cite journal |last1=LeCun |first1=Y. |display-authors=etal |year= 1998|title=Gradient-based learning applied to document recognition |url= |journal=Proceedings of the IEEE |volume=86 |issue=11 |pages=2278–2324 |doi=10.1109/5.726791}}</ref> CNNs also have been applied to [[acoustic model]]ing for automatic speech recognition (ASR).<ref name=":2" /> - -==== Challenges ==== -As with ANNs, many issues can arise with naively trained DNNs. Two common issues are [[overfitting]] and computation time. - -DNNs are prone to overfitting because of the added layers of abstraction, which allow them to model rare dependencies in the training data. [[Regularization (mathematics)|Regularization]] methods such as Ivakhnenko's unit pruning<ref name="ivak1971"/> or [[weight decay]] (<math> \ell_2 </math>-regularization) or [[sparse matrix|sparsity]] (<math> \ell_1 </math>-regularization) can be applied during training to combat overfitting.<ref>{{Cite book |doi=10.1109/icassp.2013.6639349|isbn=978-1-4799-0356-6|arxiv=1212.0901|citeseerx=10.1.1.752.9151|chapter=Advances in optimizing recurrent networks|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8624–8628|year=2013|last1=Bengio|first1=Yoshua|last2=Boulanger-Lewandowski|first2=Nicolas|last3=Pascanu|first3=Razvan}}</ref> Alternatively dropout regularization randomly omits units from the hidden layers during training. This helps to exclude rare dependencies.<ref name="DAHL2013">{{Cite journal|last=Dahl|first=G.|display-authors=etal|date=2013|title=Improving DNNs for LVCSR using rectified linear units and dropout|url=http://www.cs.toronto.edu/~gdahl/papers/reluDropoutBN_icassp2013.pdf|journal=ICASSP|pages=|via=}}</ref> Finally, data can be augmented via methods such as cropping and rotating such that smaller training sets can be increased in size to reduce the chances of overfitting.<ref>{{Cite web|url=https://www.coursera.org/learn/convolutional-neural-networks/lecture/AYzbX/data-augmentation|title=Data Augmentation - deeplearning.ai {{!}} Coursera|website=Coursera|accessdate=2017-11-30}}</ref> - -DNNs must consider many training parameters, such as the size (number of layers and number of units per layer), the [[learning rate]], and initial weights. [[Hyperparameter optimization#Grid search|Sweeping through the parameter space]] for optimal parameters may not be feasible due to the cost in time and computational resources. Various tricks, such as batching (computing the gradient on several training examples at once rather than individual examples)<ref name="RBMTRAIN">{{Cite journal|last=Hinton|first=G. E.|date=2010|title=A Practical Guide to Training Restricted Boltzmann Machines|url=https://www.researchgate.net/publication/221166159|journal=Tech. Rep. UTML TR 2010-003|pages=|via=}}</ref> speed up computation. Large processing capabilities of many-core architectures (such as GPUs or the Intel Xeon Phi) have produced significant speedups in training, because of the suitability of such processing architectures for the matrix and vector computations.<ref>{{cite book|last1=You|first1=Yang|title=Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis on - SC '17|pages=1–12|last2=Buluç|first2=Aydın|last3=Demmel|first3=James|chapter=Scaling deep learning on GPU and knights landing clusters|chapter-url=https://dl.acm.org/citation.cfm?doid=3126908.3126912|publisher=SC '17, ACM|date=November 2017|accessdate=5 March 2018|doi=10.1145/3126908.3126912|isbn=9781450351140|url=http://www.escholarship.org/uc/item/6ch40821}}</ref><ref>{{cite journal|last1=Viebke|first1=André|last2=Memeti|first2=Suejb|last3=Pllana|first3=Sabri|last4=Abraham|first4=Ajith|title=CHAOS: a parallelization scheme for training convolutional neural networks on Intel Xeon Phi|journal=The Journal of Supercomputing|volume=75|pages=197–227|doi=10.1007/s11227-017-1994-x|accessdate=|arxiv=1702.07908|bibcode=2017arXiv170207908V|url=https://www.semanticscholar.org/paper/aa8a4d2de94cc0a8ccff21f651c005613e8ec0e8|year=2019}}</ref> - -Alternatively, engineers may look for other types of neural networks with more straightforward and convergent training algorithms. CMAC ([[cerebellar model articulation controller]]) is one such kind of neural network. It doesn't require learning rates or randomized initial weights for CMAC. The training process can be guaranteed to converge in one step with a new batch of data, and the computational complexity of the training algorithm is linear with respect to the number of neurons involved.<ref name=Qin1>Ting Qin, et al. "A learning algorithm of CMAC based on RLS." Neural Processing Letters 19.1 (2004): 49-61.</ref><ref name=Qin2>Ting Qin, et al. "[http://www-control.eng.cam.ac.uk/Homepage/papers/cued_control_997.pdf Continuous CMAC-QRLS and its systolic array]." Neural Processing Letters 22.1 (2005): 1-16.</ref> - -== Applications == - -=== Automatic speech recognition === -{{Main|Speech recognition}} - -Large-scale automatic speech recognition is the first and most convincing successful case of deep learning. LSTM RNNs can learn "Very Deep Learning" tasks<ref name="SCHIDHUB"/> that involve multi-second intervals containing speech events separated by thousands of discrete time steps, where one time step corresponds to about 10 ms. LSTM with forget gates<ref name=":10" /> is competitive with traditional speech recognizers on certain tasks.<ref name="graves2003"/> - -The initial success in speech recognition was based on small-scale recognition tasks based on TIMIT. The data set contains 630 speakers from eight major [[dialect]]s of [[American English]], where each speaker reads 10 sentences.<ref name="LDCTIMIT">''TIMIT Acoustic-Phonetic Continuous Speech Corpus'' Linguistic Data Consortium, Philadelphia.</ref> Its small size lets many configurations be tried. More importantly, the TIMIT task concerns phone-sequence recognition, which, unlike word-sequence recognition, allows weak phone [[bigram]] language models. This lets the strength of the acoustic modeling aspects of speech recognition be more easily analyzed. The error rates listed below, including these early results and measured as percent phone error rates (PER), have been summarized since 1991. - -{| class="wikitable" -|- -! Method !! Percent phone<br>error rate (PER) (%) -|- -| Randomly Initialized RNN<ref>{{cite journal |last1=Robinson |first1=Tony |authorlink=Tony Robinson (speech recognition)|title=Several Improvements to a Recurrent Error Propagation Network Phone Recognition System |journal=Cambridge University Engineering Department Technical Report |date=30 September 1991 |volume=CUED/F-INFENG/TR82 |doi=10.13140/RG.2.2.15418.90567 }}</ref>|| 26.1 -|- -| Bayesian Triphone GMM-HMM || 25.6 -|- -| Hidden Trajectory (Generative) Model|| 24.8 -|- -| Monophone Randomly Initialized DNN|| 23.4 -|- -| Monophone DBN-DNN|| 22.4 -|- -| Triphone GMM-HMM with BMMI Training|| 21.7 -|- -| Monophone DBN-DNN on fbank || 20.7 -|- -| Convolutional DNN<ref name="CNN-2014">{{cite journal|last1=Abdel-Hamid|first1=O.|title=Convolutional Neural Networks for Speech Recognition|journal=IEEE/ACM Transactions on Audio, Speech, and Language Processing|date=2014|volume=22|issue=10|pages=1533–1545|doi=10.1109/taslp.2014.2339736|display-authors=etal|url=https://zenodo.org/record/891433}}</ref>|| 20.0 -|- -| Convolutional DNN w. Heterogeneous Pooling|| 18.7 -|- -| Ensemble DNN/CNN/RNN<ref name="EnsembleDL">{{cite journal|last2=Platt|first2=J.|date=2014|title=Ensemble Deep Learning for Speech Recognition|url=https://pdfs.semanticscholar.org/8201/55ecb57325503183253b8796de5f4535eb16.pdf|journal=Proc. Interspeech|pages=|via=|last1=Deng|first1=L.}}</ref>|| 18.3 -|- -| Bidirectional LSTM|| 17.9 -|- -| Hierarchical Convolutional Deep Maxout Network<ref name="HCDMM">{{cite journal|last1=Tóth|first1=Laszló|date=2015|title=Phone Recognition with Hierarchical Convolutional Deep Maxout Networks|journal=EURASIP Journal on Audio, Speech, and Music Processing|volume=2015|doi=10.1186/s13636-015-0068-3|url=http://publicatio.bibl.u-szeged.hu/5976/1/EURASIP2015.pdf}}</ref> || 16.5 -|} - -The debut of DNNs for speaker recognition in the late 1990s and speech recognition around 2009-2011 and of LSTM around 2003-2007, accelerated progress in eight major areas:<ref name="BOOK2014" /><ref name="interspeech2014Keynote" /><ref name="ReferenceA" /> - -* Scale-up/out and accelerated DNN training and decoding -* Sequence discriminative training -* Feature processing by deep models with solid understanding of the underlying mechanisms -* Adaptation of DNNs and related deep models -* [[Multi-task learning|Multi-task]] and [[Inductive transfer|transfer learning]] by DNNs and related deep models -* CNNs and how to design them to best exploit [[domain knowledge]] of speech -* RNN and its rich LSTM variants -* Other types of deep models including tensor-based models and integrated deep generative/discriminative models. - -All major commercial speech recognition systems (e.g., Microsoft [[Cortana (software)|Cortana]], [[Xbox]], [[Skype Translator]], [[Amazon Alexa]], [[Google Now]], [[Siri|Apple Siri]], [[Baidu]] and [[IFlytek|iFlyTek]] voice search, and a range of [[Nuance Communications|Nuance]] speech products, etc.) are based on deep learning.<ref name=BOOK2014 /><ref>{{Cite journal|url=https://www.wired.com/2014/12/skype-used-ai-build-amazing-new-language-translator/|title=How Skype Used AI to Build Its Amazing New Language Translator {{!}} WIRED|journal=Wired|accessdate=2017-06-14|date=2014-12-17|last1=McMillan|first1=Robert}}</ref><ref name="Baidu">{{cite arxiv |eprint=1412.5567|last1=Hannun|first1=Awni|title=Deep Speech: Scaling up end-to-end speech recognition|last2=Case|first2=Carl|last3=Casper|first3=Jared|last4=Catanzaro|first4=Bryan|last5=Diamos|first5=Greg|last6=Elsen|first6=Erich|last7=Prenger|first7=Ryan|last8=Satheesh|first8=Sanjeev|last9=Sengupta|first9=Shubho|last10=Coates|first10=Adam|last11=Ng|first11=Andrew Y|class=cs.CL|year=2014}}</ref><ref>{{Cite web|url=http://research.microsoft.com/en-US/people/deng/ieee-icassp-plenary-2016-mar24-lideng-posted.pdf|title=Plenary presentation at ICASSP-2016|date=|website=|accessdate=}}</ref> - -=== Image recognition === -{{Main|Computer vision}} - -A common evaluation set for image classification is the MNIST database data set. MNIST is composed of handwritten digits and includes 60,000 training examples and 10,000 test examples. As with TIMIT, its small size lets users test multiple configurations. A comprehensive list of results on this set is available.<ref name="YANNMNIST">{{cite web|url=http://yann.lecun.com/exdb/mnist/.|title=MNIST handwritten digit database, Yann LeCun, Corinna Cortes and Chris Burges|website=yann.lecun.com}}</ref> - -Deep learning-based image recognition has become "superhuman", producing more accurate results than human contestants. This first occurred in 2011.<ref name=":7">{{Cite journal|last=Cireşan|first=Dan|last2=Meier|first2=Ueli|last3=Masci|first3=Jonathan|last4=Schmidhuber|first4=Jürgen|date=August 2012|title=Multi-column deep neural network for traffic sign classification|journal=Neural Networks|series=Selected Papers from IJCNN 2011|volume=32|pages=333–338|doi=10.1016/j.neunet.2012.02.023|pmid=22386783|citeseerx=10.1.1.226.8219}}</ref> - -Deep learning-trained vehicles now interpret 360° camera views.<ref>[http://www.technologyreview.com/news/533936/nvidia-demos-a-car-computer-trained-with-deep-learning/ Nvidia Demos a Car Computer Trained with "Deep Learning"] (2015-01-06), David Talbot, ''[[MIT Technology Review]]''</ref> Another example is Facial Dysmorphology Novel Analysis (FDNA) used to analyze cases of human malformation connected to a large database of genetic syndromes. - -=== Visual art processing === -Closely related to the progress that has been made in image recognition is the increasing application of deep learning techniques to various visual art tasks. DNNs have proven themselves capable, for example, of a) identifying the style period of a given painting, b) [[Neural Style Transfer]] - capturing the style of a given artwork and applying it in a visually pleasing manner to an arbitrary photograph or video, and c) generating striking imagery based on random visual input fields.<ref>{{cite journal |author1=G. W. Smith|author2=Frederic Fol Leymarie|date=10 April 2017|title=The Machine as Artist: An Introduction|journal=Arts|volume=6|issue=4|pages=5|doi=10.3390/arts6020005}}</ref><ref>{{cite journal |author=Blaise Agüera y Arcas|date=29 September 2017|title=Art in the Age of Machine Intelligence|journal=Arts|volume=6|issue=4|pages=18|doi=10.3390/arts6040018}}</ref> - -=== Natural language processing === -{{Main|Natural language processing}} -Neural networks have been used for implementing language models since the early 2000s.<ref name="gers2001" /><ref>{{Cite journal|last=Bengio|first=Yoshua|last2=Ducharme|first2=Réjean|last3=Vincent|first3=Pascal|last4=Janvin|first4=Christian|date=March 2003|title=A Neural Probabilistic Language Model|url=http://dl.acm.org/citation.cfm?id=944919.944966|journal=J. Mach. Learn. Res.|volume=3|pages=1137–1155|issn=1532-4435}}</ref> LSTM helped to improve machine translation and language modeling.<ref name="NIPS2014" /><ref name="vinyals2016" /><ref name="gillick2015" /> - -Other key techniques in this field are negative sampling<ref name="GoldbergLevy2014">{{cite arXiv|last1=Goldberg|first1=Yoav|last2=Levy|first2=Omar|title=word2vec Explained: Deriving Mikolov et al.'s Negative-Sampling Word-Embedding Method|eprint=1402.3722|class=cs.CL|year=2014}}</ref> and [[word embedding]]. Word embedding, such as ''[[word2vec]]'', can be thought of as a representational layer in a deep learning architecture that transforms an atomic word into a positional representation of the word relative to other words in the dataset; the position is represented as a point in a [[vector space]]. Using word embedding as an RNN input layer allows the network to parse sentences and phrases using an effective compositional vector grammar. A compositional vector grammar can be thought of as [[probabilistic context free grammar]] (PCFG) implemented by an RNN.<ref name="SocherManning2014">{{cite web|last1=Socher|first1=Richard|last2=Manning|first2=Christopher|title=Deep Learning for NLP|url=http://nlp.stanford.edu/courses/NAACL2013/NAACL2013-Socher-Manning-DeepLearning.pdf|accessdate=26 October 2014}}</ref> Recursive auto-encoders built atop word embeddings can assess sentence similarity and detect paraphrasing.<ref name="SocherManning2014" /> Deep neural architectures provide the best results for [[Statistical parsing|constituency parsing]],<ref>{{Cite journal |url= http://aclweb.org/anthology/P/P13/P13-1045.pdf|title = Parsing With Compositional Vector Grammars|last = Socher|first = Richard|date = 2013|journal = Proceedings of the ACL 2013 Conference|accessdate = |doi = |pmid = |last2 = Bauer|first2 = John|last3 = Manning|first3 = Christopher|last4 = Ng|first4 = Andrew}}</ref> [[sentiment analysis]],<ref>{{Cite journal |url= http://nlp.stanford.edu/~socherr/EMNLP2013_RNTN.pdf|title = Recursive Deep Models for Semantic Compositionality Over a Sentiment Treebank|last = Socher|first = Richard|date = 2013 |accessdate = |doi = |pmid =}}</ref> information retrieval,<ref>{{Cite journal|last=Shen|first=Yelong|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Mesnil|first5=Gregoire|date=2014-11-01|title=A Latent Semantic Model with Convolutional-Pooling Structure for Information Retrieval|url=https://www.microsoft.com/en-us/research/publication/a-latent-semantic-model-with-convolutional-pooling-structure-for-information-retrieval/|journal=Microsoft Research}}</ref><ref>{{Cite journal|last=Huang|first=Po-Sen|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Acero|first5=Alex|last6=Heck|first6=Larry|date=2013-10-01|title=Learning Deep Structured Semantic Models for Web Search using Clickthrough Data|url=https://www.microsoft.com/en-us/research/publication/learning-deep-structured-semantic-models-for-web-search-using-clickthrough-data/|journal=Microsoft Research}}</ref> spoken language understanding,<ref name="IEEE-TASL2015">{{cite journal | last1 = Mesnil | first1 = G. | last2 = Dauphin | first2 = Y. | last3 = Yao | first3 = K. | last4 = Bengio | first4 = Y. | last5 = Deng | first5 = L. | last6 = Hakkani-Tur | first6 = D. | last7 = He | first7 = X. | last8 = Heck | first8 = L. | last9 = Tur | first9 = G. | last10 = Yu | first10 = D. | last11 = Zweig | first11 = G. | year = 2015 | title = Using recurrent neural networks for slot filling in spoken language understanding | url= https://www.semanticscholar.org/paper/41911ef90a225a82597a2b576346759ea9c34247| journal = IEEE Transactions on Audio, Speech, and Language Processing | volume = 23 | issue = 3| pages = 530–539 | doi=10.1109/taslp.2014.2383614}}</ref> machine translation,<ref name="NIPS2014">{{Cite journal|last=Sutskever|first=L.|last2=Vinyals|first2=O.|last3=Le|first3=Q.|date=2014|title=Sequence to Sequence Learning with Neural Networks|url=https://papers.nips.cc/paper/5346-sequence-to-sequence-learning-with-neural-networks.pdf|journal=Proc. NIPS|pages=|via=|bibcode=2014arXiv1409.3215S|arxiv=1409.3215}}</ref><ref name="auto">{{Cite journal|last=Gao|first=Jianfeng|last2=He|first2=Xiaodong|last3=Yih|first3=Scott Wen-tau|last4=Deng|first4=Li|date=2014-06-01|title=Learning Continuous Phrase Representations for Translation Modeling|url=https://www.microsoft.com/en-us/research/publication/learning-continuous-phrase-representations-for-translation-modeling/|journal=Microsoft Research}}</ref> contextual entity linking,<ref name="auto"/> writing style recognition,<ref name="BROC2017">{{Cite journal |doi = 10.1002/dac.3259|title = Authorship verification using deep belief network systems|journal = International Journal of Communication Systems|volume = 30|issue = 12|pages = e3259|year = 2017|last1 = Brocardo|first1 = Marcelo Luiz|last2 = Traore|first2 = Issa|last3 = Woungang|first3 = Isaac|last4 = Obaidat|first4 = Mohammad S.}}</ref> Text classification and others.<ref>{{Cite news|url=https://www.microsoft.com/en-us/research/project/deep-learning-for-natural-language-processing-theory-and-practice-cikm2014-tutorial/|title=Deep Learning for Natural Language Processing: Theory and Practice (CIKM2014 Tutorial) - Microsoft Research|work=Microsoft Research|accessdate=2017-06-14}}</ref> - -Recent developments generalize [[word embedding]] to [[sentence embedding]]. - -[[Google Translate]] (GT) uses a large [[End-to-end principle|end-to-end]] long short-term memory network.<ref name="GT_Turovsky_2016">{{cite web|url=https://blog.google/products/translate/found-translation-more-accurate-fluent-sentences-google-translate/|title=Found in translation: More accurate, fluent sentences in Google Translate|last=Turovsky|first=Barak|date=November 15, 2016|website=The Keyword Google Blog|accessdate=March 23, 2017}}</ref><ref name="googleblog_GNMT_2016">{{cite web|url=https://research.googleblog.com/2016/11/zero-shot-translation-with-googles.html|title=Zero-Shot Translation with Google's Multilingual Neural Machine Translation System|last1=Schuster|first1=Mike|last2=Johnson|first2=Melvin|date=November 22, 2016|website=Google Research Blog|accessdate=March 23, 2017|last3=Thorat|first3=Nikhil}}</ref><ref name="lstm1997">{{Cite journal|author=Sepp Hochreiter|author2=Jürgen Schmidhuber|year=1997|title=Long short-term memory|url=https://www.researchgate.net/publication/13853244|journal=[[Neural Computation (journal)|Neural Computation]]|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|pmid=9377276|via=}}</ref><ref name="lstm2000">{{Cite journal|author=Felix A. Gers|author2=Jürgen Schmidhuber|author3=Fred Cummins|year=2000|title=Learning to Forget: Continual Prediction with LSTM|journal=[[Neural Computation (journal)|Neural Computation]]|volume=12|issue=10|pages=2451–2471|doi=10.1162/089976600300015015|pmid=11032042|citeseerx=10.1.1.55.5709|url=https://www.semanticscholar.org/paper/11540131eae85b2e11d53df7f1360eeb6476e7f4}}</ref><ref name="GoogleTranslate">{{cite arXiv |eprint=1609.08144|last1=Wu|first1=Yonghui|title=Google's Neural Machine Translation System: Bridging the Gap between Human and Machine Translation|last2=Schuster|first2=Mike|last3=Chen|first3=Zhifeng|last4=Le|first4=Quoc V|last5=Norouzi|first5=Mohammad|last6=Macherey|first6=Wolfgang|last7=Krikun|first7=Maxim|last8=Cao|first8=Yuan|last9=Gao|first9=Qin|last10=Macherey|first10=Klaus|last11=Klingner|first11=Jeff|last12=Shah|first12=Apurva|last13=Johnson|first13=Melvin|last14=Liu|first14=Xiaobing|last15=Kaiser|first15=Łukasz|last16=Gouws|first16=Stephan|last17=Kato|first17=Yoshikiyo|last18=Kudo|first18=Taku|last19=Kazawa|first19=Hideto|last20=Stevens|first20=Keith|last21=Kurian|first21=George|last22=Patil|first22=Nishant|last23=Wang|first23=Wei|last24=Young|first24=Cliff|last25=Smith|first25=Jason|last26=Riesa|first26=Jason|last27=Rudnick|first27=Alex|last28=Vinyals|first28=Oriol|last29=Corrado|first29=Greg|last30=Hughes|first30=Macduff|display-authors=29|class=cs.CL|year=2016}}</ref><ref name="WiredGoogleTranslate">"An Infusion of AI Makes Google Translate More Powerful Than Ever." Cade Metz, WIRED, Date of Publication: 09.27.16. https://www.wired.com/2016/09/google-claims-ai-breakthrough-machine-translation/</ref> [[Google Neural Machine Translation|Google Neural Machine Translation (GNMT)]] uses an [[example-based machine translation]] method in which the system "learns from millions of examples."<ref name="googleblog_GNMT_2016" /> It translates "whole sentences at a time, rather than pieces. Google Translate supports over one hundred languages.<ref name="googleblog_GNMT_2016" /> The network encodes the "semantics of the sentence rather than simply memorizing phrase-to-phrase translations".<ref name="googleblog_GNMT_2016" /><ref name="Biotet">{{cite web|url=http://www-clips.imag.fr/geta/herve.blanchon/Pdfs/NLP-KE-10.pdf|title=MT on and for the Web|last1=Boitet|first1=Christian|last2=Blanchon|first2=Hervé|date=2010|accessdate=December 1, 2016|last3=Seligman|first3=Mark|last4=Bellynck|first4=Valérie}}</ref> GT uses English as an intermediate between most language pairs.<ref name="Biotet" /> - -=== Drug discovery and toxicology === -{{For|more information|Drug discovery|Toxicology}} -A large percentage of candidate drugs fail to win regulatory approval. These failures are caused by insufficient efficacy (on-target effect), undesired interactions (off-target effects), or unanticipated [[Toxicity|toxic effects]].<ref name="ARROWSMITH2013">{{Cite journal -| pmid = 23903212 -| year = 2013 -| last1 = Arrowsmith -| first1 = J -| title = Trial watch: Phase II and phase III attrition rates 2011-2012 -| journal = Nature Reviews Drug Discovery -| volume = 12 -| issue = 8 -| pages = 569 -| last2 = Miller -| first2 = P -| doi = 10.1038/nrd4090 -| url = https://www.semanticscholar.org/paper/9ab0f468a64762ca5069335c776e1ab07fa2b3e2 -}}</ref><ref name="VERBIEST2015">{{Cite journal -| pmid = 25582842 -| year = 2015 -| last1 = Verbist -| first1 = B -| title = Using transcriptomics to guide lead optimization in drug discovery projects: Lessons learned from the QSTAR project -| journal = Drug Discovery Today -| last2 = Klambauer -| first2 = G -| last3 = Vervoort -| first3 = L -| last4 = Talloen -| first4 = W -| last5 = The Qstar -| first5 = Consortium -| last6 = Shkedy -| first6 = Z -| last7 = Thas -| first7 = O -| last8 = Bender -| first8 = A -| last9 = Göhlmann -| first9 = H. W. -| last10 = Hochreiter -| first10 = S -| doi = 10.1016/j.drudis.2014.12.014 -| volume=20 -| issue = 5 -| pages=505–513 -}}</ref> Research has explored use of deep learning to predict the [[biomolecular target]]s,<ref name="MERCK2012" /><ref name=":5" /> [[off-target]]s, and [[Toxicity|toxic effects]] of environmental chemicals in nutrients, household products and drugs.<ref name="TOX21" /><ref name="TOX21Data" /><ref name=":11" /> - -AtomNet is a deep learning system for structure-based [[Drug design|rational drug design]].<ref>{{cite arXiv|title = AtomNet: A Deep Convolutional Neural Network for Bioactivity Prediction in Structure-based Drug Discovery|eprint= 1510.02855|date = 2015-10-09|first = Izhar|last = Wallach|first2 = Michael|last2 = Dzamba|first3 = Abraham|last3 = Heifets|class= cs.LG}}</ref> AtomNet was used to predict novel candidate biomolecules for disease targets such as the [[Ebola virus]]<ref>{{Cite news|title = Toronto startup has a faster way to discover effective medicines |url= https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/|website = The Globe and Mail |accessdate= 2015-11-09}}</ref> and [[multiple sclerosis]].<ref>{{Cite web|title = Startup Harnesses Supercomputers to Seek Cures |url= http://ww2.kqed.org/futureofyou/2015/05/27/startup-harnesses-supercomputers-to-seek-cures/|website = KQED Future of You|accessdate = 2015-11-09}}</ref><ref>{{cite web|url=https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/%5D%20and%20multiple%20sclerosis%20%5B/|title=Toronto startup has a faster way to discover effective medicines}}</ref> - -In 2019 generative neural networks were used to produce molecules that were validated experimentally all the way into mice.<ref>{{cite journal |last1=Zhavoronkov |first1=Alex|date=2019|title=Deep learning enables rapid identification of potent DDR1 kinase inhibitors |journal=Nature Biotechnology |volume=37|issue=9|pages=1038–1040|doi=10.1038/s41587-019-0224-x |pmid=31477924|url=https://www.semanticscholar.org/paper/d44ac0a7fd4734187bccafc4a2771027b8bb595e}}</ref><ref>{{cite journal |last1=Gregory |first1=Barber |title=A Molecule Designed By AI Exhibits 'Druglike' Qualities |url=https://www.wired.com/story/molecule-designed-ai-exhibits-druglike-qualities/ |journal=Wired}}</ref> - -=== Customer relationship management === -{{Main|Customer relationship management}} -Deep reinforcement learning has been used to approximate the value of possible [[direct marketing]] actions, defined in terms of [[RFM (customer value)|RFM]] variables. The estimated value function was shown to have a natural interpretation as [[customer lifetime value]].<ref>{{cite arxiv|last=Tkachenko |first=Yegor |title=Autonomous CRM Control via CLV Approximation with Deep Reinforcement Learning in Discrete and Continuous Action Space |date=April 8, 2015 |eprint=1504.01840|class=cs.LG }}</ref> - -=== Recommendation systems === -{{Main|Recommender system}} -Recommendation systems have used deep learning to extract meaningful features for a latent factor model for content-based music and journal recommendations.<ref>{{Cite book|url=http://papers.nips.cc/paper/5004-deep-content-based-music-recommendation.pdf|title=Advances in Neural Information Processing Systems 26|last=van den Oord|first=Aaron|last2=Dieleman|first2=Sander|last3=Schrauwen|first3=Benjamin|date=2013|publisher=Curran Associates, Inc.|editor-last=Burges|editor-first=C. J. C.|pages=2643–2651|editor-last2=Bottou|editor-first2=L.|editor-last3=Welling|editor-first3=M.|editor-last4=Ghahramani|editor-first4=Z.|editor-last5=Weinberger|editor-first5=K. Q.}}</ref><ref>X.Y. Feng, H. Zhang, Y.J. Ren, P.H. Shang, Y. Zhu, Y.C. Liang, R.C. Guan, D. Xu, (2019), "[https://www.jmir.org/2019/5/e12957/ The Deep Learning–Based Recommender System “Pubmender” for Choosing a Biomedical Publication Venue: Development and Validation Study]", ''[[Journal of Medical Internet Research]]'', 21 (5): e12957</ref> Multiview deep learning has been applied for learning user preferences from multiple domains.<ref>{{Cite journal|last=Elkahky|first=Ali Mamdouh|last2=Song|first2=Yang|last3=He|first3=Xiaodong|date=2015-05-01|title=A Multi-View Deep Learning Approach for Cross Domain User Modeling in Recommendation Systems|url=https://www.microsoft.com/en-us/research/publication/a-multi-view-deep-learning-approach-for-cross-domain-user-modeling-in-recommendation-systems/|journal=Microsoft Research}}</ref> The model uses a hybrid collaborative and content-based approach and enhances recommendations in multiple tasks. - -=== Bioinformatics === -{{Main|Bioinformatics}} -An [[autoencoder]] ANN was used in [[bioinformatics]], to predict [[Gene Ontology|gene ontology]] annotations and gene-function relationships.<ref>{{cite book|title=Deep Autoencoder Neural Networks for Gene Ontology Annotation Predictions |first1=Davide |last1=Chicco|first2=Peter|last2=Sadowski|first3=Pierre |last3=Baldi |date=1 January 2014|publisher=ACM|pages=533–540|doi=10.1145/2649387.2649442|journal=Proceedings of the 5th ACM Conference on Bioinformatics, Computational Biology, and Health Informatics - BCB '14|isbn=9781450328944 |hdl = 11311/964622|url=https://www.semanticscholar.org/paper/09f3132fdf103bdef1125ffbccb8b46f921b2ab7 }}</ref> - -In medical informatics, deep learning was used to predict sleep quality based on data from wearables<ref>{{Cite journal|last=Sathyanarayana|first=Aarti|date=2016-01-01|title=Sleep Quality Prediction From Wearable Data Using Deep Learning|journal=JMIR mHealth and uHealth|volume=4|issue=4|doi=10.2196/mhealth.6562|pmid=27815231|pmc=5116102|pages=e125|url=https://www.semanticscholar.org/paper/c82884f9d6d39c8a89ac46b8f688669fb2931144}}</ref> and predictions of health complications from [[electronic health record]] data.<ref>{{Cite journal|last=Choi|first=Edward|last2=Schuetz|first2=Andy|last3=Stewart|first3=Walter F.|last4=Sun|first4=Jimeng|date=2016-08-13|title=Using recurrent neural network models for early detection of heart failure onset|url=http://jamia.oxfordjournals.org/content/early/2016/08/13/jamia.ocw112|journal=Journal of the American Medical Informatics Association|volume=24|issue=2|pages=361–370|doi=10.1093/jamia/ocw112|issn=1067-5027|pmid=27521897|pmc=5391725}}</ref> Deep learning has also showed efficacy in [[Artificial intelligence in healthcare|healthcare]].<ref>{{Cite web|url=https://medium.com/the-mission/deep-learning-in-healthcare-challenges-and-opportunities-d2eee7e2545|title=Deep Learning in Healthcare: Challenges and Opportunities|date=2016-08-12|website=Medium|access-date=2018-04-10}}</ref> - -=== Medical Image Analysis === -Deep learning has been shown to produce competitive results in medical application such as cancer cell classification, lesion detection, organ segmentation and image enhancement<ref>{{Cite journal|last=Litjens|first=Geert|last2=Kooi|first2=Thijs|last3=Bejnordi|first3=Babak Ehteshami|last4=Setio|first4=Arnaud Arindra Adiyoso|last5=Ciompi|first5=Francesco|last6=Ghafoorian|first6=Mohsen|last7=van der Laak|first7=Jeroen A.W.M.|last8=van Ginneken|first8=Bram|last9=Sánchez|first9=Clara I.|date=December 2017|title=A survey on deep learning in medical image analysis|journal=Medical Image Analysis|volume=42|pages=60–88|doi=10.1016/j.media.2017.07.005|pmid=28778026|arxiv=1702.05747|bibcode=2017arXiv170205747L|url=https://www.semanticscholar.org/paper/2abde28f75a9135c8ed7c50ea16b7b9e49da0c09}}</ref><ref>{{Cite book |doi=10.1109/ICCVW.2017.18|isbn=9781538610343|chapter=Deep Convolutional Neural Networks for Detecting Cellular Changes Due to Malignancy|title=2017 IEEE International Conference on Computer Vision Workshops (ICCVW)|pages=82–89|year=2017|last1=Forslid|first1=Gustav|last2=Wieslander|first2=Hakan|last3=Bengtsson|first3=Ewert|last4=Wahlby|first4=Carolina|last5=Hirsch|first5=Jan-Michael|last6=Stark|first6=Christina Runow|last7=Sadanandan|first7=Sajith Kecheril|chapter-url=http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326160|url=https://www.semanticscholar.org/paper/6ae67bb4528bd5d922fd5a0c1a180ff1940f803c}}</ref> - -=== Mobile advertising === -Finding the appropriate mobile audience for [[mobile advertising]] is always challenging, since many data points must be considered and analyzed before a target segment can be created and used in ad serving by any ad server.<ref>{{cite book |doi=10.1109/CSCITA.2017.8066548 |isbn=978-1-5090-4381-1|chapter=Predicting the popularity of instagram posts for a lifestyle magazine using deep learning|title=2017 2nd International Conference on Communication Systems, Computing and IT Applications (CSCITA)|pages=174–177|year=2017|last1=De|first1=Shaunak|last2=Maity|first2=Abhishek|last3=Goel|first3=Vritti|last4=Shitole|first4=Sanjay|last5=Bhattacharya|first5=Avik|chapter-url=https://www.semanticscholar.org/paper/c4389f8a63a7be58e007c183a49e491141f9e204}}</ref> Deep learning has been used to interpret large, many-dimensioned advertising datasets. Many data points are collected during the request/serve/click internet advertising cycle. This information can form the basis of machine learning to improve ad selection. - -=== Image restoration === -Deep learning has been successfully applied to [[inverse problems]] such as [[denoising]], [[super-resolution]], [[inpainting]], and [[film colorization]].<ref>{{Cite web|url=https://blog.floydhub.com/colorizing-and-restoring-old-images-with-deep-learning/|title=Colorizing and Restoring Old Images with Deep Learning|date=2018-11-13|website=FloydHub Blog|language=en|access-date=2019-10-11}}</ref> These applications include learning methods such as "Shrinkage Fields for Effective Image Restoration"<ref>{{cite conference | url= http://research.uweschmidt.org/pubs/cvpr14schmidt.pdf |first1= Uwe |last1= Schmidt |first2= Stefan |last2= Roth |conference= Computer Vision and Pattern Recognition (CVPR), 2014 IEEE Conference on |title= Shrinkage Fields for Effective Image Restoration }}</ref> which trains on an image dataset, and [[Deep Image Prior]], which trains on the image that needs restoration. - -=== Financial fraud detection === -Deep learning is being successfully applied to financial [[fraud detection]] and anti-money laundering. "Deep anti-money laundering detection system can spot and recognize relationships and similarities between data and, further down the road, learn to detect anomalies or classify and predict specific events". The solution leverages both supervised learning techniques, such as the classification of suspicious transactions, and unsupervised learning, e.g. anomaly detection. -<ref>{{cite journal -|first=Tomasz |last=Czech -|title=Deep learning: the next frontier for money laundering detection -|url=https://www.globalbankingandfinance.com/deep-learning-the-next-frontier-for-money-laundering-detection/ -|journal=Global Banking and Finance Review -}}</ref> - -=== Military === - -The United States Department of Defense applied deep learning to train robots in new tasks through observation.<ref name=":12">{{Cite web|url=https://www.eurekalert.org/pub_releases/2018-02/uarl-ard020218.php|title=Army researchers develop new algorithms to train robots|website=EurekAlert!|access-date=2018-08-29}}</ref> - -== Relation to human cognitive and brain development == -Deep learning is closely related to a class of theories of [[brain development]] (specifically, neocortical development) proposed by [[cognitive neuroscientist]]s in the early 1990s.<ref name="UTGOFF">{{cite journal | last1 = Utgoff | first1 = P. E. | last2 = Stracuzzi | first2 = D. J. | year = 2002 | title = Many-layered learning | url= https://www.semanticscholar.org/paper/398c477f674b228fec7f3f418a8cec047e2dafe5| journal = Neural Computation | volume = 14 | issue = 10| pages = 2497–2529 | doi=10.1162/08997660260293319| pmid = 12396572 }}</ref><ref name="ELMAN">{{cite book|url={{google books |plainurl=y |id=vELaRu_MrwoC}}|title=Rethinking Innateness: A Connectionist Perspective on Development|last=Elman|first=Jeffrey L.|publisher=MIT Press|year=1998|isbn=978-0-262-55030-7}}</ref><ref name="SHRAGER">{{cite journal | last1 = Shrager | first1 = J. | last2 = Johnson | first2 = MH | year = 1996 | title = Dynamic plasticity influences the emergence of function in a simple cortical array | url= | journal = Neural Networks | volume = 9 | issue = 7| pages = 1119–1129 | doi=10.1016/0893-6080(96)00033-0| pmid = 12662587 }}</ref><ref name="QUARTZ">{{cite journal | last1 = Quartz | first1 = SR | last2 = Sejnowski | first2 = TJ | year = 1997 | title = The neural basis of cognitive development: A constructivist manifesto | url= | journal = Behavioral and Brain Sciences | volume = 20 | issue = 4| pages = 537–556 | doi=10.1017/s0140525x97001581| pmid = 10097006 | citeseerx = 10.1.1.41.7854 }}</ref> These developmental theories were instantiated in computational models, making them predecessors of deep learning systems. These developmental models share the property that various proposed learning dynamics in the brain (e.g., a wave of [[nerve growth factor]]) support the [[self-organization]] somewhat analogous to the neural networks utilized in deep learning models. Like the [[neocortex]], neural networks employ a hierarchy of layered filters in which each layer considers information from a prior layer (or the operating environment), and then passes its output (and possibly the original input), to other layers. This process yields a self-organizing stack of [[transducer]]s, well-tuned to their operating environment. A 1995 description stated, "...the infant's brain seems to organize itself under the influence of waves of so-called trophic-factors ... different regions of the brain become connected sequentially, with one layer of tissue maturing before another and so on until the whole brain is mature."<ref name="BLAKESLEE">S. Blakeslee., "In brain's early growth, timetable may be critical," ''The New York Times, Science Section'', pp. B5–B6, 1995.</ref> - -A variety of approaches have been used to investigate the plausibility of deep learning models from a neurobiological perspective. On the one hand, several variants of the [[backpropagation]] algorithm have been proposed in order to increase its processing realism.<ref>{{Cite journal|last=Mazzoni|first=P.|last2=Andersen|first2=R. A.|last3=Jordan|first3=M. I.|date=1991-05-15|title=A more biologically plausible learning rule for neural networks.|journal=Proceedings of the National Academy of Sciences|volume=88|issue=10|pages=4433–4437|doi=10.1073/pnas.88.10.4433|issn=0027-8424|pmid=1903542|pmc=51674|bibcode=1991PNAS...88.4433M}}</ref><ref>{{Cite journal|last=O'Reilly|first=Randall C.|date=1996-07-01|title=Biologically Plausible Error-Driven Learning Using Local Activation Differences: The Generalized Recirculation Algorithm|journal=Neural Computation|volume=8|issue=5|pages=895–938|doi=10.1162/neco.1996.8.5.895|issn=0899-7667|url=https://www.semanticscholar.org/paper/ed9133009dd451bd64215cca7deba6e0b8d7c7b1}}</ref> Other researchers have argued that unsupervised forms of deep learning, such as those based on hierarchical [[generative model]]s and [[deep belief network]]s, may be closer to biological reality.<ref>{{Cite journal|last=Testolin|first=Alberto|last2=Zorzi|first2=Marco|date=2016|title=Probabilistic Models and Generative Neural Networks: Towards an Unified Framework for Modeling Normal and Impaired Neurocognitive Functions|journal=Frontiers in Computational Neuroscience|volume=10|pages=73|doi=10.3389/fncom.2016.00073|pmid=27468262|pmc=4943066|issn=1662-5188|url=https://www.semanticscholar.org/paper/9ff36a621ee2c831fbbda5b719942f9ed8ac844f}}</ref><ref>{{Cite journal|last=Testolin|first=Alberto|last2=Stoianov|first2=Ivilin|last3=Zorzi|first3=Marco|date=September 2017|title=Letter perception emerges from unsupervised deep learning and recycling of natural image features|journal=Nature Human Behaviour|volume=1|issue=9|pages=657–664|doi=10.1038/s41562-017-0186-2|pmid=31024135|issn=2397-3374|url=https://www.semanticscholar.org/paper/ec2463bd610dcb30d67681160e895761e2dde482}}</ref> In this respect, generative neural network models have been related to neurobiological evidence about sampling-based processing in the cerebral cortex.<ref>{{Cite journal|last=Buesing|first=Lars|last2=Bill|first2=Johannes|last3=Nessler|first3=Bernhard|last4=Maass|first4=Wolfgang|date=2011-11-03|title=Neural Dynamics as Sampling: A Model for Stochastic Computation in Recurrent Networks of Spiking Neurons|journal=PLOS Computational Biology|volume=7|issue=11|pages=e1002211|doi=10.1371/journal.pcbi.1002211|pmid=22096452|pmc=3207943|issn=1553-7358|bibcode=2011PLSCB...7E2211B|url=https://www.semanticscholar.org/paper/e4e100e44bf7618c7d96188605fd9870012bdb50}}</ref> - -Although a systematic comparison between the human brain organization and the neuronal encoding in deep networks has not yet been established, several analogies have been reported. For example, the computations performed by deep learning units could be similar to those of actual neurons<ref>{{Cite journal|last=Morel|first=Danielle|last2=Singh|first2=Chandan|last3=Levy|first3=William B.|date=2018-01-25|title=Linearization of excitatory synaptic integration at no extra cost|journal=Journal of Computational Neuroscience|volume=44|issue=2|pages=173–188|doi=10.1007/s10827-017-0673-5|pmid=29372434|issn=0929-5313|url=https://www.semanticscholar.org/paper/3a528f2cde957d4e6417651f8005ca2ee81ca367}}</ref><ref>{{Cite journal|last=Cash|first=S.|last2=Yuste|first2=R.|date=February 1999|title=Linear summation of excitatory inputs by CA1 pyramidal neurons|journal=Neuron|volume=22|issue=2|pages=383–394|issn=0896-6273|pmid=10069343|doi=10.1016/s0896-6273(00)81098-3}}</ref> and neural populations.<ref>{{Cite journal|date=2004-08-01|title=Sparse coding of sensory inputs|journal=Current Opinion in Neurobiology|volume=14|issue=4|pages=481–487|doi=10.1016/j.conb.2004.07.007|pmid=15321069|issn=0959-4388 | last1 = Olshausen | first1 = B | last2 = Field | first2 = D|url=https://www.semanticscholar.org/paper/0dd289358b14f8176adb7b62bf2fb53ea62b3818}}</ref> Similarly, the representations developed by deep learning models are similar to those measured in the primate visual system<ref>{{Cite journal|last=Yamins|first=Daniel L K|last2=DiCarlo|first2=James J|date=March 2016|title=Using goal-driven deep learning models to understand sensory cortex|journal=Nature Neuroscience|volume=19|issue=3|pages=356–365|doi=10.1038/nn.4244|pmid=26906502|issn=1546-1726|url=https://www.semanticscholar.org/paper/94c4ba7246f781632aa68ca5b1acff0fdbb2d92f}}</ref> both at the single-unit<ref>{{Cite journal|last=Zorzi|first=Marco|last2=Testolin|first2=Alberto|date=2018-02-19|title=An emergentist perspective on the origin of number sense|journal=Phil. Trans. R. Soc. B|volume=373|issue=1740|pages=20170043|doi=10.1098/rstb.2017.0043|issn=0962-8436|pmid=29292348|pmc=5784047|url=https://www.semanticscholar.org/paper/c91db0c8349a78384f54c6a9a98370f5c9381b6c}}</ref> and at the population<ref>{{Cite journal|last=Güçlü|first=Umut|last2=van Gerven|first2=Marcel A. J.|date=2015-07-08|title=Deep Neural Networks Reveal a Gradient in the Complexity of Neural Representations across the Ventral Stream|journal=Journal of Neuroscience|volume=35|issue=27|pages=10005–10014|doi=10.1523/jneurosci.5023-14.2015|pmid=26157000|pmc=6605414|arxiv=1411.6422}}</ref> levels. - -== Commercial activity == -[[Facebook]]'s AI lab performs tasks such as [[Automatic image annotation|automatically tagging uploaded pictures]] with the names of the people in them.<ref name="METZ2013">{{cite magazine|first=C. |last=Metz |title=Facebook's 'Deep Learning' Guru Reveals the Future of AI |url=https://www.wired.com/wiredenterprise/2013/12/facebook-yann-lecun-qa/ |magazine=Wired |date=12 December 2013}}</ref> - -Google's [[DeepMind Technologies]] developed a system capable of learning how to play [[Atari]] video games using only pixels as data input. In 2015 they demonstrated their [[AlphaGo]] system, which learned the game of [[Go (game)|Go]] well enough to beat a professional Go player.<ref>{{Cite web|title = Google AI algorithm masters ancient game of Go |url= http://www.nature.com/news/google-ai-algorithm-masters-ancient-game-of-go-1.19234|website = Nature News & Comment|accessdate = 2016-01-30}}</ref><ref>{{Cite journal|title = Mastering the game of Go with deep neural networks and tree search|journal = [[Nature (journal)|Nature]]| issn= 0028-0836|pages = 484–489|volume = 529|issue = 7587|doi = 10.1038/nature16961|pmid = 26819042|first1 = David|last1 = Silver|author-link1=David Silver (programmer)|first2 = Aja|last2 = Huang|author-link2=Aja Huang|first3 = Chris J.|last3 = Maddison|first4 = Arthur|last4 = Guez|first5 = Laurent|last5 = Sifre|first6 = George van den|last6 = Driessche|first7 = Julian|last7 = Schrittwieser|first8 = Ioannis|last8 = Antonoglou|first9 = Veda|last9 = Panneershelvam|first10= Marc|last10= Lanctot|first11= Sander|last11= Dieleman|first12=Dominik|last12= Grewe|first13= John|last13= Nham|first14= Nal|last14= Kalchbrenner|first15= Ilya|last15= Sutskever|author-link15=Ilya Sutskever|first16= Timothy|last16= Lillicrap|first17= Madeleine|last17= Leach|first18= Koray|last18= Kavukcuoglu|first19= Thore|last19= Graepel|first20= Demis |last20=Hassabis|author-link20=Demis Hassabis|date= 28 January 2016|bibcode = 2016Natur.529..484S|url = https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}{{closed access}}</ref><ref>{{Cite web|title = A Google DeepMind Algorithm Uses Deep Learning and More to Master the Game of Go {{!}} MIT Technology Review |url= http://www.technologyreview.com/news/546066/googles-ai-masters-the-game-of-go-a-decade-earlier-than-expected/|website = MIT Technology Review|accessdate = 2016-01-30}}</ref> [[Google Translate]] uses a neural network to translate between more than 100 languages. - -In 2015, [[Blippar]] demonstrated a mobile [[augmented reality]] application that uses deep learning to recognize objects in real time.<ref>{{Cite web|title=Blippar Demonstrates New Real-Time Augmented Reality App|url=https://techcrunch.com/2015/12/08/blippar-demonstrates-new-real-time-augmented-reality-app/|website=TechCrunch}}</ref> - -In 2017, Covariant.ai was launched, which focuses on integrating deep learning into factories.<ref>[https://www.nytimes.com/2017/11/06/technology/artificial-intelligence-start-up.html A.I. Researchers Leave Elon Musk Lab to Begin Robotics Start-Up]</ref> - -As of 2008,<ref>{{Cite document|title=TAMER: Training an Agent Manually via Evaluative Reinforcement - IEEE Conference Publication|doi=10.1109/DEVLRN.2008.4640845}}</ref> researchers at [[University of Texas at Austin|The University of Texas at Austin]] (UT) developed a machine learning framework called Training an Agent Manually via Evaluative Reinforcement, or TAMER, which proposed new methods for robots or computer programs to learn how to perform tasks by interacting with a human instructor.<ref name=":12" /> First developed as TAMER, a new algorithm called Deep TAMER was later introduced in 2018 during a collaboration between [[U.S. Army Research Laboratory]] (ARL) and UT researchers. Deep TAMER used deep learning to provide a robot the ability to learn new tasks through observation.<ref name=":12" /> Using Deep TAMER, a robot learned a task with a human trainer, watching video streams or observing a human perform a task in-person. The robot later practiced the task with the help of some coaching from the trainer, who provided feedback such as “good job” and “bad job.”<ref>{{Cite web|url=https://governmentciomedia.com/talk-algorithms-ai-becomes-faster-learner|title=Talk to the Algorithms: AI Becomes a Faster Learner|website=governmentciomedia.com|access-date=2018-08-29}}</ref> - -== Criticism and comment == -Deep learning has attracted both criticism and comment, in some cases from outside the field of computer science. - -=== Theory === -{{see also|Explainable AI}} -A main criticism concerns the lack of theory surrounding some methods.<ref>{{Cite web|url=https://medium.com/@GaryMarcus/in-defense-of-skepticism-about-deep-learning-6e8bfd5ae0f1|title=In defense of skepticism about deep learning|last=Marcus|first=Gary|date=2018-01-14|website=Gary Marcus|access-date=2018-10-11}}</ref> Learning in the most common deep architectures is implemented using well-understood gradient descent. However, the theory surrounding other algorithms, such as contrastive divergence is less clear.{{citation needed|date=July 2016}} (e.g., Does it converge? If so, how fast? What is it approximating?) Deep learning methods are often looked at as a [[black box]], with most confirmations done empirically, rather than theoretically.<ref name="Knight 2017">{{cite web | last=Knight | first=Will | title=DARPA is funding projects that will try to open up AI's black boxes | website=MIT Technology Review | date=2017-03-14 | url=https://www.technologyreview.com/s/603795/the-us-military-wants-its-autonomous-machines-to-explain-themselves/ | accessdate=2017-11-02}}</ref> - -Others point out that deep learning should be looked at as a step towards realizing strong AI, not as an all-encompassing solution. Despite the power of deep learning methods, they still lack much of the functionality needed for realizing this goal entirely. Research psychologist Gary Marcus noted:<blockquote>"Realistically, deep learning is only part of the larger challenge of building intelligent machines. Such techniques lack ways of representing [[causality|causal relationships]] (...) have no obvious ways of performing [[inference|logical inferences]], and they are also still a long way from integrating abstract knowledge, such as information about what objects are, what they are for, and how they are typically used. The most powerful A.I. systems, like [[Watson (computer)|Watson]] (...) use techniques like deep learning as just one element in a very complicated ensemble of techniques, ranging from the statistical technique of [[Bayesian inference]] to [[deductive reasoning]]."<ref>{{cite magazine|url=https://www.newyorker.com/|title=Is "Deep Learning" a Revolution in Artificial Intelligence?|last=Marcus|first=Gary|date=November 25, 2012|magazine=The New Yorker|accessdate=2017-06-14}}</ref></blockquote>As an alternative to this emphasis on the limits of deep learning, one author speculated that it might be possible to train a machine vision stack to perform the sophisticated task of discriminating between "old master" and amateur figure drawings, and hypothesized that such a sensitivity might represent the rudiments of a non-trivial machine empathy.<ref>{{cite web|url=http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|title=Art and Artificial Intelligence|date=March 27, 2015|publisher=ArtEnt|author=Smith, G. W.|accessdate=March 27, 2015|url-status=bot: unknown|archiveurl=https://web.archive.org/web/20170625075845/http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|archivedate=June 25, 2017}}</ref> This same author proposed that this would be in line with anthropology, which identifies a concern with aesthetics as a key element of [[behavioral modernity]].<ref>{{cite web |url=http://repositriodeficheiros.yolasite.com/resources/Texto%2028.pdf |author=Mellars, Paul |date=February 1, 2005 |title=The Impossible Coincidence: A Single-Species Model for the Origins of Modern Human Behavior in Europe|publisher=Evolutionary Anthropology: Issues, News, and Reviews |accessdate=April 5, 2017}}</ref> - -In further reference to the idea that artistic sensitivity might inhere within relatively low levels of the cognitive hierarchy, a published series of graphic representations of the internal states of deep (20-30 layers) neural networks attempting to discern within essentially random data the images on which they were trained<ref>{{cite web|url=http://googleresearch.blogspot.co.uk/2015/06/inceptionism-going-deeper-into-neural.html |author1=Alexander Mordvintsev |author2=Christopher Olah |author3=Mike Tyka |date=June 17, 2015 |title=Inceptionism: Going Deeper into Neural Networks |publisher=Google Research Blog |accessdate=June 20, 2015}}</ref> demonstrate a visual appeal: the original research notice received well over 1,000 comments, and was the subject of what was for a time the most frequently accessed article on ''[[The Guardian]]'s''<ref>{{cite news|url=https://www.theguardian.com/technology/2015/jun/18/google-image-recognition-neural-network-androids-dream-electric-sheep|title=Yes, androids do dream of electric sheep|date=June 18, 2015|newspaper=The Guardian|author=Alex Hern|accessdate=June 20, 2015}}</ref> website. - -=== Errors === -Some deep learning architectures display problematic behaviors,<ref name=goertzel>{{cite web|first=Ben |last=Goertzel |title=Are there Deep Reasons Underlying the Pathologies of Today's Deep Learning Algorithms? |year=2015 |url=http://goertzel.org/DeepLearning_v1.pdf}}</ref> such as confidently classifying unrecognizable images as belonging to a familiar category of ordinary images<ref>{{cite arxiv |eprint=1412.1897|last1=Nguyen|first1=Anh|title=Deep Neural Networks are Easily Fooled: High Confidence Predictions for Unrecognizable Images|last2=Yosinski|first2=Jason|last3=Clune|first3=Jeff|class=cs.CV|year=2014}}</ref> and misclassifying minuscule perturbations of correctly classified images.<ref>{{cite arxiv |eprint=1312.6199|last1=Szegedy|first1=Christian|title=Intriguing properties of neural networks|last2=Zaremba|first2=Wojciech|last3=Sutskever|first3=Ilya|last4=Bruna|first4=Joan|last5=Erhan|first5=Dumitru|last6=Goodfellow|first6=Ian|last7=Fergus|first7=Rob|class=cs.CV|year=2013}}</ref> [[Ben Goertzel|Goertzel]] hypothesized that these behaviors are due to limitations in their internal representations and that these limitations would inhibit integration into heterogeneous multi-component [[artificial general intelligence]] (AGI) architectures.<ref name="goertzel" /> These issues may possibly be addressed by deep learning architectures that internally form states homologous to image-grammar<ref>{{cite journal | last1 = Zhu | first1 = S.C. | last2 = Mumford | first2 = D. | year = 2006| title = A stochastic grammar of images | url= | journal = Found. Trends Comput. Graph. Vis. | volume = 2 | issue = 4| pages = 259–362 | doi = 10.1561/0600000018| citeseerx = 10.1.1.681.2190 }}</ref> decompositions of observed entities and events.<ref name="goertzel"/> [[Grammar induction|Learning a grammar]] (visual or linguistic) from training data would be equivalent to restricting the system to [[commonsense reasoning]] that operates on concepts in terms of grammatical [[Production (computer science)|production rules]] and is a basic goal of both human language acquisition<ref>Miller, G. A., and N. Chomsky. "Pattern conception." Paper for Conference on pattern detection, University of Michigan. 1957.</ref> and [[artificial intelligence]] (AI).<ref>{{cite web|first=Jason |last=Eisner |title=Deep Learning of Recursive Structure: Grammar Induction |url=http://techtalks.tv/talks/deep-learning-of-recursive-structure-grammar-induction/58089/}}</ref> - -=== Cyber threat === -As deep learning moves from the lab into the world, research and experience shows that artificial neural networks are vulnerable to hacks and deception.<ref>{{Cite web|url=https://gizmodo.com/hackers-have-already-started-to-weaponize-artificial-in-1797688425|title=Hackers Have Already Started to Weaponize Artificial Intelligence|website=Gizmodo|access-date=2019-10-11}}</ref> By identifying patterns that these systems use to function, attackers can modify inputs to ANNs in such a way that the ANN finds a match that human observers would not recognize. For example, an attacker can make subtle changes to an image such that the ANN finds a match even though the image looks to a human nothing like the search target. Such a manipulation is termed an “adversarial attack.”<ref>{{Cite web|url=https://www.dailydot.com/debug/adversarial-attacks-ai-mistakes/|title=How hackers can force AI to make dumb mistakes|date=2018-06-18|website=The Daily Dot|language=en|access-date=2019-10-11}}</ref> In 2016 researchers used one ANN to doctor images in trial and error fashion, identify another's focal points and thereby generate images that deceived it. The modified images looked no different to human eyes. Another group showed that printouts of doctored images then photographed successfully tricked an image classification system.<ref name=":4">{{Cite news|url=https://singularityhub.com/2017/10/10/ai-is-easy-to-fool-why-that-needs-to-change|title=AI Is Easy to Fool—Why That Needs to Change|last=|first=|date=2017-10-10|work=Singularity Hub|accessdate=2017-10-11}}</ref> One defense is reverse image search, in which a possible fake image is submitted to a site such as [[TinEye]] that can then find other instances of it. A refinement is to search using only parts of the image, to identify images from which that piece may have been taken'''.'''<ref>{{Cite journal|last=Gibney|first=Elizabeth|title=The scientist who spots fake videos|url=https://www.nature.com/news/the-scientist-who-spots-fake-videos-1.22784|journal=Nature|pages=|doi=10.1038/nature.2017.22784|via=|year=2017}}</ref> - -Another group showed that certain [[Psychedelic art|psychedelic]] spectacles could fool a [[facial recognition system]] into thinking ordinary people were celebrities, potentially allowing one person to impersonate another. In 2017 researchers added stickers to [[stop sign]]s and caused an ANN to misclassify them.<ref name=":4" /> - -ANNs can however be further trained to detect attempts at deception, potentially leading attackers and defenders into an arms race similar to the kind that already defines the [[malware]] defense industry. ANNs have been trained to defeat ANN-based anti-malware software by repeatedly attacking a defense with malware that was continually altered by a [[genetic algorithm]] until it tricked the anti-malware while retaining its ability to damage the target.<ref name=":4" /> - -Another group demonstrated that certain sounds could make the [[Google Now]] voice command system open a particular web address that would download malware.<ref name=":4" /> - -In “data poisoning,” false data is continually smuggled into a machine learning system's training set to prevent it from achieving mastery.<ref name=":4" /> - -=== Reliance on human [[microwork]] === -Most Deep Learning systems rely on training and verification data that is generated and/or annotated by humans. It has been argued in [[Media studies|media philosophy]] that not only low-paid [[Clickworkers|clickwork]] (e.g. on [[Amazon Mechanical Turk]]) is regularly deployed for this purpose, but also implicit forms of human [[microwork]] that are often not recognized as such.<ref name=":13">{{Cite journal|last=Mühlhoff|first=Rainer|date=2019-11-06|title=Human-aided artificial intelligence: Or, how to run large computations in human brains? Toward a media sociology of machine learning|journal=New Media & Society|language=en|volume=|pages=146144481988533|doi=10.1177/1461444819885334|issn=1461-4448}}</ref> The philosopher Rainer Mühlhoff distinguishes five types of "machinic capture" of human microwork to generate training data: (1) [[gamification]] (the embedding of annotation or computation tasks in the flow of a game), (2) "trapping and tracking" (e.g. [[CAPTCHA]]s for image recognition or click-tracking on Google [[Search engine results page|search results pages]]), (3) exploitation of social motivations (e.g. [[Tag (Facebook)|tagging faces]] on [[Facebook]] to obtain labeled facial images), (4) [[information mining]] (e.g. by leveraging [[Quantified self|quantified-self]] devices such as [[activity tracker]]s) and (5) [[Clickworkers|clickwork]].<ref name=":13" /> Mühlhoff argues that in most commercial end-user applications of Deep Learning such as [[DeepFace|Facebook's face recognition system,]] the need for training data does not stop once an ANN is trained. Rather, there is a continued demand for human-generated verification data to constantly calibrate and update the ANN. For this purpose Facebook introduced the feature that once a user is automatically recognized in an image, they receive a notification. They can choose whether of not they like to be publicly labeled on the image, or tell Facebook that it is not them in the picture.<ref>{{Cite news|url=https://www.wired.com/story/facebook-will-find-your-face-even-when-its-not-tagged/|title=Facebook Can Now Find Your Face, Even When It's Not Tagged|work=Wired|access-date=2019-11-22|language=en|issn=1059-1028}}</ref> This user interface is a mechanism to generate "a constant stream of  verification data"<ref name=":13" /> to further train the network in real-time. As Mühlhoff argues, involvement of human users to generate training and verification data is so typical for most commercial end-user applications of Deep Learning that such systems may be referred to as "human-aided artificial intelligence".<ref name=":13" /> - -== Shallowing deep neural networks == - -{{technical|section|date=February 2020}} -Shallowing refers to reducing a pre-trained DNN to a smaller network with the same or similar performance.<ref>{{cite journal |last1= Chen|first1= S.|last2= Zhao|first2=Q.|date= 2018|title=Shallowing deep networks: Layer-wise pruning based on feature representations |url= |journal=Representations. IEEE Transactions on Pattern Analysis and Machine Intelligence |volume= 41|issue=12 |pages= 3048–56|doi=10.1109/TPAMI.2018.2874634 |pmid= 30296213|access-date=}}</ref> Training of DNN with further shallowing can produce more efficient systems than just training of smaller networks from scratch. Shallowing is the rebirth of pruning that developed in the 1980-1990s.<ref name= "Hassibi1993">{{cite conference -| url = -| title = Optimal brain surgeon and general network pruning -| last1 = Hassibi -| first1 = B. -| last2 = Stork -| first2 = D. G. -| last3 = Wolff -| first3 = G. J. -| date = 1993 -| publisher = IEEE -| book-title = IEEE International Conference on Neural Networks -| pages = 293–299 -| volume = 1 -| location = San Francisco, CA, USA -| doi = 10.1109/ICNN.1993.298572 -}}</ref><ref name= "Gordienko1993"> -{{cite conference -| url = -| title = Construction of efficient neural networks: algorithms and tests -| last1 = Gordienko -| first1 = P. -| date = 1993 -| publisher = IEEE -| book-title = Proceedings of 1993 International Conference on Neural Networks (IJCNN-93) -| pages = 313–6 -| volume = 1 -| location = Nagoya, Japan -| doi = 10.1109/IJCNN.1993.713920 -}}</ref> The main approach to pruning is to gradually remove network elements (synapses, neurons, blocks of neurons, or layers) that have little impact on performance evaluation. Various indicators of sensitivity are used that estimate the changes of performance after pruning. The simplest indicators use just values of transmitted signals and the synaptic weights (the zeroth order). More complex indicators use mean absolute values of partial derivatives of the cost function,<ref name= "Gordienko1993"/><ref name="GorbMirTsar1999">{{cite conference -| url = -| title = Generation of explicit knowledge from empirical data through pruning of trainable neural networks -| last1 = Gorban -| first1 = A. N. -| last2 = Mirkes -| first2 = E. M. -| last3 = Tsaregorodtsev -| first3 = V. G. -| date = 1999 -| publisher = IEEE -| book-title = IJCNN'99. International Joint Conference on Neural Networks. Proceedings (Cat. No.99CH36339) -| pages = 4393–4398 -| location = Washington, DC, USA -| doi = 10.1109/IJCNN.1999.830876 -| arxiv = cond-mat/0307083 -}}</ref> -or even the second derivatives.<ref name= "Hassibi1993"/> The shallowing allows to reduce the necessary resources and makes the skills of neural network more explicit.<ref name="GorbMirTsar1999"/> It is used for image classification,<ref>{{cite journal |last1=Zhong |first1= G.|last2= Yan|first2= S.|last3= Huang|first3= K.|last4=Cai|first4=Y.|last5=Dong |first5= J.|date=2018|title= Reducing and stretching deep convolutional activation features for accurate image classification|url= |journal= Cogn. Comput.|volume= 10|issue= 1|pages=179–86|doi=10.1007/s12559-017-9515-z |access-date=}}</ref> for development of security systems,<ref name="MirkesDog2019">{{cite journal |last1=Gorban |first1= A. N.|last2=Mirkes |first2=E. M. |last3=Tyukin |first3= I. Y.|date= 2019|title=How deep should be the depth of convolutional neural networks: A backyard dog case study |url= |journal=Cogn. Comput.|volume= |issue= |pages= |doi= 10.1007/s12559-019-09667-7 | doi-access= free| arxiv= 1805.01516 }}</ref> for accelerating DNN execution on mobile devices,<ref>{{cite conference -| url = https://www.aaai.org/ocs/index.php/AAAI/AAAI18/paper/viewFile/16652/15946 -| title = DeepRebirth: Accelerating deep neural network execution on mobile devices -| last1 = Li -| first1 = D. -| last2 = Wang -| first2 = X. -| last3 = Kong -| first3 = D. -| date = 2018 -| publisher = Association for the Advancement of Artificial Intelligence -| book-title = Thirty-second AAAI conference on artificial intelligence (AAAI-18) -| pages = -| location = -| doi = -| arxiv = 1708.04728 -}} -</ref> and for other applications. It has been demonstrated that using linear postprocessing, such as supervised PCA, improves DNN performance after shallowing.<ref name="MirkesDog2019"/> - -== See also == -* [[Applications of artificial intelligence]] -* [[Comparison of deep learning software]] -* [[Compressed sensing]] -* [[Echo state network]] -* [[List of artificial intelligence projects]] -* [[Liquid state machine]] -* [[List of datasets for machine learning research]] -* [[Reservoir computing]] -* [[Sparse coding]] - -== References == -{{Reflist|30em}} - -== Further reading == -{{refbegin}} -* {{cite book |title=Deep Learning |year=2016 -|first1=Ian |last1=Goodfellow |authorlink1=Ian Goodfellow -|first2=Yoshua |last2=Bengio |authorlink2=Yoshua Bengio -|first3=Aaron |last3=Courville -|publisher=MIT Press -|url=http://www.deeplearningbook.org -|isbn=978-0-26203561-3 -|postscript=, introductory textbook. -}} - -{{Prone to spam|date=June 2015}}{{Z148}}<!-- {{No more links}} - -Please be cautious adding more external links. - -Wikipedia is not a collection of links and should not be used for advertising. - -Excessive or inappropriate links will be removed. - - See [[Wikipedia:External links]] and [[Wikipedia:Spam]] for details. - -If there are already suitable links, propose additions or replacements on -the article's talk page, or submit your link to the relevant category at -DMOZ (dmoz.org) and link there using {{Dmoz}}. - ---> - -[[Category:Deep learning| ]] -[[Category:Artificial neural networks]] -[[Category:Artificial intelligence]] -[[Category:Emerging technologies]] +[http://204.152.217.73/ 204.152.217.73] '
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[ 0 => '{{About||deep versus shallow learning in educational psychology|Student approaches to learning|more information|Artificial neural network}}', 1 => '{{short description|Branch of machine learning}}', 2 => '{{machine learning bar}}', 3 => ''''Deep learning''' (also known as '''deep structured learning''' or '''differential programming''') is part of a broader family of [[machine learning]] methods based on [[artificial neural networks]] with [[representation learning]]. Learning can be [[Supervised learning|supervised]], [[Semi-supervised learning|semi-supervised]] or [[Unsupervised learning|unsupervised]].<ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="NatureBengio">{{cite journal |last1=Bengio |first1=Yoshua |last2=LeCun |first2= Yann| last3=Hinton | first3= Geoffrey|year=2015 |title=Deep Learning |journal=Nature |volume=521 |issue=7553 |pages=436–444 |doi=10.1038/nature14539 |pmid=26017442|bibcode=2015Natur.521..436L |url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256 }}</ref>', 4 => 'Deep learning architectures such as [[#Deep_neural_networks|deep neural network]]s, [[deep belief network]]s, [[recurrent neural networks]] and [[convolutional neural networks]] have been applied to fields including [[computer vision]], [[automatic speech recognition|speech recognition]], [[natural language processing]], [[audio recognition]], social network filtering, [[machine translation]], [[bioinformatics]], [[drug design]], medical image analysis, material inspection and [[board game]] programs, where they have produced results comparable to and in some cases surpassing human expert performance.<ref name=":9">{{Cite book |doi=10.1109/cvpr.2012.6248110 |isbn=978-1-4673-1228-8|arxiv=1202.2745|chapter=Multi-column deep neural networks for image classification|title=2012 IEEE Conference on Computer Vision and Pattern Recognition|pages=3642–3649|year=2012|last1=Ciresan|first1=D.|last2=Meier|first2=U.|last3=Schmidhuber|first3=J.}}</ref><ref name="krizhevsky2012">{{cite journal|last1=Krizhevsky|first1=Alex|last2=Sutskever|first2=Ilya|last3=Hinton|first3=Geoffry|date=2012|title=ImageNet Classification with Deep Convolutional Neural Networks|url=https://www.cs.toronto.edu/~kriz/imagenet_classification_with_deep_convolutional.pdf|journal=NIPS 2012: Neural Information Processing Systems, Lake Tahoe, Nevada}}', 5 => '</ref><ref>{{cite web |title=Google's AlphaGo AI wins three-match series against the world's best Go player |url=https://techcrunch.com/2017/05/24/alphago-beats-planets-best-human-go-player-ke-jie/amp/ |website=TechCrunch |date=25 May 2017}}</ref>', 6 => '[[Artificial neural network]]s (ANNs) were inspired by information processing and distributed communication nodes in biological systems. ANNs have various differences from biological [[brain]]s. Specifically, neural networks tend to be static and symbolic, while the biological brain of most living organisms is dynamic (plastic) and analog.<ref>{{Cite journal|last=Marblestone|first=Adam H.|last2=Wayne|first2=Greg|last3=Kording|first3=Konrad P.|date=2016|title=Toward an Integration of Deep Learning and Neuroscience |journal=Frontiers in Computational Neuroscience |volume=10|pages=94|doi=10.3389/fncom.2016.00094 |pmc=5021692|pmid=27683554|bibcode=2016arXiv160603813M|arxiv=1606.03813|url=https://www.semanticscholar.org/paper/2dec4f52b1ce552b416f086d4ea1040626675dfa}}</ref><ref>{{cite journal|last1=Olshausen|first1=B. A.|year=1996|title=Emergence of simple-cell receptive field properties by learning a sparse code for natural images|journal=Nature|volume=381|issue=6583|pages=607–609|bibcode=1996Natur.381..607O|doi=10.1038/381607a0|pmid=8637596|url=https://www.semanticscholar.org/paper/8012c4a1e2ca663f1a04e80cbb19631a00cbab27}}</ref><ref>{{cite arxiv|last=Bengio|first=Yoshua|last2=Lee|first2=Dong-Hyun|last3=Bornschein|first3=Jorg|last4=Mesnard|first4=Thomas|last5=Lin|first5=Zhouhan|date=2015-02-13|title=Towards Biologically Plausible Deep Learning|eprint=1502.04156|class=cs.LG}}</ref>', 7 => '{{toclimit|3}}', 8 => '', 9 => '== Definition ==', 10 => '[[File:Deep Learning.jpg|alt=Representing Images on Multiple Layers of Abstraction in Deep Learning|thumb|Representing Images on Multiple Layers of Abstraction in Deep Learning <ref>{{Cite journal|last=Schulz|first=Hannes|last2=Behnke|first2=Sven|date=2012-11-01|title=Deep Learning|journal=KI - Künstliche Intelligenz|language=en|volume=26|issue=4|pages=357–363|doi=10.1007/s13218-012-0198-z|issn=1610-1987|url=https://www.semanticscholar.org/paper/51a80649d16a38d41dbd20472deb3bc9b61b59a0}}</ref>]]', 11 => 'Deep learning is a class of [[machine learning]] [[algorithm]]s that<ref name="BOOK2014">{{cite journal|last2=Yu|first2=D.|year=2014|title=Deep Learning: Methods and Applications|url=http://research.microsoft.com/pubs/209355/DeepLearning-NowPublishing-Vol7-SIG-039.pdf|journal=Foundations and Trends in Signal Processing|volume=7|issue=3–4|pages=1–199|doi=10.1561/2000000039|last1=Deng|first1=L.}}</ref>{{rp|pages=199–200}} uses multiple layers to progressively extract higher level features from the raw input. For example, in [[image processing]], lower layers may identify edges, while higher layers may identify the concepts relevant to a human such as digits or letters or faces.', 12 => '', 13 => '== Overview ==', 14 => 'Most modern deep learning models are based on artificial neural networks, specifically, [[Convolutional Neural Network]]s (CNN)s, although they can also include [[propositional formula]]s or latent variables organized layer-wise in deep [[generative model]]s such as the nodes in [[deep belief network]]s and deep [[Boltzmann machine]]s.<ref name="BENGIODEEP">{{cite journal|last=Bengio|first=Yoshua|year=2009|title=Learning Deep Architectures for AI|url=http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20%282009%29.pdf|journal=Foundations and Trends in Machine Learning|volume=2|issue=1|pages=1–127|doi=10.1561/2200000006|citeseerx=10.1.1.701.9550|access-date=2015-09-03|archive-url=https://web.archive.org/web/20160304084250/http://sanghv.com/download/soft/machine%20learning,%20artificial%20intelligence,%20mathematics%20ebooks/ML/learning%20deep%20architectures%20for%20AI%20(2009).pdf|archive-date=2016-03-04|url-status=dead}}</ref>', 15 => '', 16 => 'In deep learning, each level learns to transform its input data into a slightly more abstract and composite representation. In an image recognition application, the raw input may be a [[Matrix (mathematics)|matrix]] of pixels; the first representational layer may abstract the pixels and encode edges; the second layer may compose and encode arrangements of edges; the third layer may encode a nose and eyes; and the fourth layer may recognize that the image contains a face. Importantly, a deep learning process can learn which features to optimally place in which level ''on its own''. (Of course, this does not completely eliminate the need for hand-tuning; for example, varying numbers of layers and layer sizes can provide different degrees of abstraction.)<ref name="BENGIO2012">{{cite journal|last2=Courville|first2=A.|last3=Vincent|first3=P.|year=2013|title=Representation Learning: A Review and New Perspectives|journal=IEEE Transactions on Pattern Analysis and Machine Intelligence|volume=35|issue=8|pages=1798–1828|arxiv=1206.5538|doi=10.1109/tpami.2013.50|pmid=23787338|last1=Bengio|first1=Y.}}</ref><ref>{{cite journal|last1=LeCun|first1=Yann|last2=Bengio|first2=Yoshua|last3=Hinton|first3=Geoffrey|title=Deep learning|journal=Nature|date=28 May 2015|volume=521|issue=7553|pages=436–444|doi=10.1038/nature14539|pmid=26017442|bibcode=2015Natur.521..436L|url=https://www.semanticscholar.org/paper/a4cec122a08216fe8a3bc19b22e78fbaea096256}}</ref>', 17 => '', 18 => 'The word "deep" in "deep learning" refers to the number of layers through which the data is transformed. More precisely, deep learning systems have a substantial ''credit assignment path'' (CAP) depth. The CAP is the chain of transformations from input to output. CAPs describe potentially causal connections between input and output. For a [[feedforward neural network]], the depth of the CAPs is that of the network and is the number of hidden layers plus one (as the output layer is also parameterized). For [[recurrent neural network]]s, in which a signal may propagate through a layer more than once, the CAP depth is potentially unlimited.<ref name="SCHIDHUB" /> No universally agreed upon threshold of depth divides shallow learning from deep learning, but most researchers agree that deep learning involves CAP depth higher than 2. CAP of depth 2 has been shown to be a universal approximator in the sense that it can emulate any function.<ref>{{Cite book|url=https://books.google.com/books?id=9CqQDwAAQBAJ&pg=PA15&dq#v=onepage&q&f=false|title=Human Behavior and Another Kind in Consciousness: Emerging Research and Opportunities: Emerging Research and Opportunities|last=Shigeki|first=Sugiyama|date=2019-04-12|publisher=IGI Global|isbn=978-1-5225-8218-2|language=en}}</ref> Beyond that, more layers do not add to the function approximator ability of the network. Deep models (CAP > 2) are able to extract better features than shallow models and hence, extra layers help in learning the features effectively.', 19 => '', 20 => 'Deep learning architectures can be constructed with a [[greedy algorithm|greedy]] layer-by-layer method.<ref name=BENGIO2007>{{cite conference | first1=Yoshua | last1=Bengio | first2=Pascal | last2=Lamblin | first3=Dan|last3=Popovici |first4=Hugo|last4=Larochelle | title=Greedy layer-wise training of deep networks| year=2007 | url=http://papers.nips.cc/paper/3048-greedy-layer-wise-training-of-deep-networks.pdf| conference = Advances in neural information processing systems | pages= 153–160}}</ref> Deep learning helps to disentangle these abstractions and pick out which features improve performance.<ref name="BENGIO2012" />', 21 => '', 22 => 'For [[supervised learning]] tasks, deep learning methods eliminate [[feature engineering]], by translating the data into compact intermediate representations akin to [[Principal Component Analysis|principal components]], and derive layered structures that remove redundancy in representation.', 23 => '', 24 => 'Deep learning algorithms can be applied to unsupervised learning tasks. This is an important benefit because unlabeled data are more abundant than the labeled data. Examples of deep structures that can be trained in an unsupervised manner are neural history compressors<ref name="scholarpedia">Jürgen Schmidhuber (2015). Deep Learning. Scholarpedia, 10(11):32832. [http://www.scholarpedia.org/article/Deep_Learning Online]</ref> and [[deep belief network]]s.<ref name="BENGIO2012" /><ref name="SCHOLARDBNS">{{cite journal | last1 = Hinton | first1 = G.E. | year = 2009| title = Deep belief networks | url= | journal = Scholarpedia | volume = 4 | issue = 5| page = 5947 | doi=10.4249/scholarpedia.5947| bibcode = 2009SchpJ...4.5947H}}</ref>', 25 => '', 26 => '== Interpretations ==', 27 => 'Deep neural networks are generally interpreted in terms of the [[universal approximation theorem]]<ref name="ReferenceB">Balázs Csanád Csáji (2001). Approximation with Artificial Neural Networks; Faculty of Sciences; Eötvös Loránd University, Hungary</ref><ref name=cyb>{{cite journal | last1 = Cybenko | year = 1989 | title = Approximations by superpositions of sigmoidal functions | url = http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | journal = [[Mathematics of Control, Signals, and Systems]] | volume = 2 | issue = 4 | pages = 303–314 | doi = 10.1007/bf02551274 | url-status = dead | archiveurl = https://web.archive.org/web/20151010204407/http://deeplearning.cs.cmu.edu/pdfs/Cybenko.pdf | archivedate = 2015-10-10 }}</ref><ref name=horn>{{cite journal | last1 = Hornik | first1 = Kurt | year = 1991 | title = Approximation Capabilities of Multilayer Feedforward Networks | url= | journal = Neural Networks | volume = 4 | issue = 2| pages = 251–257 | doi=10.1016/0893-6080(91)90009-t}}</ref><ref name="Haykin, Simon 1998">{{cite book|first=Simon S. |last=Haykin|title=Neural Networks: A Comprehensive Foundation|url={{google books |plainurl=y |id=bX4pAQAAMAAJ}}|year=1999|publisher=Prentice Hall|isbn=978-0-13-273350-2}}</ref><ref name="Hassoun, M. 1995 p. 48">{{cite book|first=Mohamad H. |last=Hassoun|title=Fundamentals of Artificial Neural Networks|url={{google books |plainurl=y |id=Otk32Y3QkxQC|page=48}}|year=1995|publisher=MIT Press|isbn=978-0-262-08239-6|p=48}}</ref><ref name=ZhouLu>Lu, Z., Pu, H., Wang, F., Hu, Z., & Wang, L. (2017). [http://papers.nips.cc/paper/7203-the-expressive-power-of-neural-networks-a-view-from-the-width The Expressive Power of Neural Networks: A View from the Width]. Neural Information Processing Systems, 6231-6239.', 28 => '</ref> or [[Bayesian inference|probabilistic inference]].<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB">{{cite journal|last=Schmidhuber|first=J.|year=2015|title=Deep Learning in Neural Networks: An Overview|journal=Neural Networks|volume=61|pages=85–117|arxiv=1404.7828|doi=10.1016/j.neunet.2014.09.003|pmid=25462637|url=https://www.semanticscholar.org/paper/126df9f24e29feee6e49e135da102fbbd9154a48}}</ref><ref name="SCHOLARDBNS" /><ref name = MURPHY>{{cite book|first=Kevin P. |last=Murphy|title=Machine Learning: A Probabilistic Perspective|url={{google books |plainurl=y |id=NZP6AQAAQBAJ}}|date=24 August 2012|publisher=MIT Press|isbn=978-0-262-01802-9}}</ref><ref name= "Patel NIPS 2016">{{Cite journal|url=https://papers.nips.cc/paper/6231-a-probabilistic-framework-for-deep-learning.pdf|title=A Probabilistic Framework for Deep Learning|last=Patel|first=Ankit|last2=Nguyen|first2=Tan|last3=Baraniuk|first3=Richard|date=2016|journal=Advances in Neural Information Processing Systems|pages=|bibcode=2016arXiv161201936P|arxiv=1612.01936}}</ref>', 29 => '', 30 => 'The classic universal approximation theorem concerns the capacity of [[feedforward neural networks]] with a single hidden layer of finite size to approximate [[continuous functions]].<ref name="ReferenceB"/><ref name="cyb"/><ref name="horn"/><ref name="Haykin, Simon 1998"/><ref name="Hassoun, M. 1995 p. 48"/> In 1989, the first proof was published by [[George Cybenko]] for [[sigmoid function|sigmoid]] activation functions<ref name="cyb" /> and was generalised to feed-forward multi-layer architectures in 1991 by Kurt Hornik.<ref name="horn" /> Recent work also showed that universal approximation also holds for non-bounded activation functions such as the rectified linear unit.<ref name=sonoda17>{{cite journal | last1 = Sonoda | first1 = Sho | last2=Murata | first2=Noboru | year = 2017 | title = Neural network with unbounded activation functions is universal approximator | journal = Applied and Computational Harmonic Analysis | volume = 43 | issue = 2 | pages = 233–268 | doi = 10.1016/j.acha.2015.12.005| arxiv = 1505.03654 | url = https://www.semanticscholar.org/paper/d0e48a4d5d6d0b4aa2dbab2c50560945e62a3817 }}</ref>', 31 => '', 32 => 'The universal approximation theorem for [[deep neural network]]s concerns the capacity of networks with bounded width but the depth is allowed to grow. Lu et al.<ref name=ZhouLu/> proved that if the width of a [[deep neural network]] with [[ReLU]] activation is strictly larger than the input dimension, then the network can approximate any [[Lebesgue integration|Lebesgue integrable function]]; If the width is smaller or equal to the input dimension, then [[deep neural network]] is not a universal approximator.', 33 => '', 34 => 'The [[probabilistic]] interpretation<ref name="MURPHY" /> derives from the field of [[machine learning]]. It features inference,<ref name="BOOK2014" /><ref name="BENGIODEEP" /><ref name="BENGIO2012" /><ref name="SCHIDHUB" /><ref name="SCHOLARDBNS" /><ref name="MURPHY" /> as well as the [[optimization]] concepts of [[training]] and [[test (assessment)|testing]], related to fitting and [[generalization]], respectively. More specifically, the probabilistic interpretation considers the activation nonlinearity as a [[cumulative distribution function]].<ref name="MURPHY" /> The probabilistic interpretation led to the introduction of [[dropout (neural networks)|dropout]] as [[Regularization (mathematics)|regularizer]] in neural networks.<ref name="DROPOUT">{{cite arXiv |last1=Hinton |first1=G. E. |last2=Srivastava| first2 =N.|last3=Krizhevsky| first3=A.| last4 =Sutskever| first4=I.| last5=Salakhutdinov| first5=R.R.|eprint=1207.0580 |class=math.LG |title=Improving neural networks by preventing co-adaptation of feature detectors |date=2012}}</ref> The probabilistic interpretation was introduced by researchers including [[John Hopfield|Hopfield]], [[Bernard Widrow|Widrow]] and [[Kumpati S. Narendra|Narendra]] and popularized in surveys such as the one by [[Christopher Bishop|Bishop]].<ref name="prml">{{cite book|title=Pattern Recognition and Machine Learning|author=Bishop, Christopher M.|year=2006|publisher=Springer|url=http://users.isr.ist.utl.pt/~wurmd/Livros/school/Bishop%20-%20Pattern%20Recognition%20And%20Machine%20Learning%20-%20Springer%20%202006.pdf|isbn=978-0-387-31073-2}}</ref>', 35 => '', 36 => '== History ==', 37 => 'The term ''Deep Learning'' was introduced to the machine learning community by [[Rina Dechter]] in 1986,<ref name="dechter1986">[[Rina Dechter]] (1986). Learning while searching in constraint-satisfaction problems. University of California, Computer Science Department, Cognitive Systems Laboratory.[https://www.researchgate.net/publication/221605378_Learning_While_Searching_in_Constraint-Satisfaction-Problems Online]</ref><ref name="scholarpedia" /> and to [[Artificial Neural Networks|artificial neural networks]] by Igor Aizenberg and colleagues in 2000, in the context of [[Boolean network|Boolean]] threshold neurons.<ref name="aizenberg2000">Igor Aizenberg, Naum N. Aizenberg, Joos P.L. Vandewalle (2000). Multi-Valued and Universal Binary Neurons: Theory, Learning and Applications. Springer Science & Business Media.</ref><ref>Co-evolving recurrent neurons learn deep memory POMDPs. Proc. GECCO, Washington, D. C., pp. 1795-1802, ACM Press, New York, NY, USA, 2005.</ref>', 38 => '', 39 => 'The first general, working learning algorithm for supervised, deep, feedforward, multilayer [[perceptron]]s was published by [[Alexey Ivakhnenko]] and Lapa in 1967.<ref name="ivak1965">{{cite book|first1=A. G. |last1=Ivakhnenko |first2=V. G. |last2=Lapa |title=Cybernetics and Forecasting Techniques|url={{google books |plainurl=y |id=rGFgAAAAMAAJ}}|year=1967|publisher=American Elsevier Publishing Co.|isbn=978-0-444-00020-0}}</ref> A 1971 paper described already a deep network with 8 layers trained by the [[group method of data handling]] algorithm.<ref name="ivak1971">{{Cite journal|last=Ivakhnenko|first=Alexey|date=1971|title=Polynomial theory of complex systems|url=http://gmdh.net/articles/history/polynomial.pdf |journal=IEEE Transactions on Systems, Man and Cybernetics |pages=364–378|doi=10.1109/TSMC.1971.4308320|pmid=|accessdate=|volume=SMC-1|issue=4}}</ref>', 40 => '', 41 => 'Other deep learning working architectures, specifically those built for [[computer vision]], began with the [[Neocognitron]] introduced by [[Kunihiko Fukushima]] in 1980.<ref name="FUKU1980">{{cite journal | last1 = Fukushima | first1 = K. | year = 1980 | title = Neocognitron: A self-organizing neural network model for a mechanism of pattern recognition unaffected by shift in position | url= | journal = Biol. Cybern. | volume = 36 | issue = 4| pages = 193–202 | doi=10.1007/bf00344251 | pmid=7370364}}</ref> In 1989, [[Yann LeCun]] et al. applied the standard backpropagation algorithm, which had been around as the reverse mode of [[automatic differentiation]] since 1970,<ref name="lin1970">[[Seppo Linnainmaa]] (1970). The representation of the cumulative rounding error of an algorithm as a Taylor expansion of the local rounding errors. Master's Thesis (in Finnish), Univ. Helsinki, 6-7.</ref><ref name="grie2012">{{Cite journal|last=Griewank|first=Andreas|date=2012|title=Who Invented the Reverse Mode of Differentiation?|url=http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|journal=Documenta Mathematica|issue=Extra Volume ISMP|pages=389–400|access-date=2017-06-11|archive-url=https://web.archive.org/web/20170721211929/http://www.math.uiuc.edu/documenta/vol-ismp/52_griewank-andreas-b.pdf|archive-date=2017-07-21|url-status=dead}}</ref><ref name="WERBOS1974">{{Cite journal|last=Werbos|first=P.|date=1974|title=Beyond Regression: New Tools for Prediction and Analysis in the Behavioral Sciences |url=https://www.researchgate.net/publication/35657389 |journal=Harvard University |accessdate=12 June 2017}}</ref><ref name="werbos1982">{{Cite book|chapter-url=ftp://ftp.idsia.ch/pub/juergen/habilitation.pdf|title=System modeling and optimization|last=Werbos|first=Paul|publisher=Springer|year=1982|isbn=|location=|pages=762–770|chapter=Applications of advances in nonlinear sensitivity analysis}}</ref> to a deep neural network with the purpose of recognizing handwritten [[ZIP code]]s on mail. While the algorithm worked, training required 3 days.<ref name="LECUN1989">LeCun ''et al.'', "Backpropagation Applied to Handwritten Zip Code Recognition," ''Neural Computation'', 1, pp. 541–551, 1989.</ref>', 42 => '', 43 => 'By 1991 such systems were used for recognizing isolated 2-D hand-written digits, while [[3D object recognition|recognizing 3-D objects]] was done by matching 2-D images with a handcrafted 3-D object model. Weng ''et al.'' suggested that a human brain does not use a monolithic 3-D object model and in 1992 they published Cresceptron,<ref name="Weng1992">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCNN1992.pdf Cresceptron: a self-organizing neural network which grows adaptively]," ''Proc. International Joint Conference on Neural Networks'', Baltimore, Maryland, vol I, pp. 576-581, June, 1992.</ref><ref name="Weng1993">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronICCV1993.pdf Learning recognition and segmentation of 3-D objects from 2-D images]," ''Proc. 4th International Conf. Computer Vision'', Berlin, Germany, pp. 121-128, May, 1993.</ref><ref name="Weng1997">J. Weng, N. Ahuja and T. S. Huang, "[http://www.cse.msu.edu/~weng/research/CresceptronIJCV.pdf Learning recognition and segmentation using the Cresceptron]," ''International Journal of Computer Vision'', vol. 25, no. 2, pp. 105-139, Nov. 1997.</ref> a method for performing 3-D object recognition in cluttered scenes. Because it directly used natural images, Cresceptron started the beginning of general-purpose visual learning for natural 3D worlds. Cresceptron is a cascade of layers similar to Neocognitron. But while Neocognitron required a human programmer to hand-merge features, Cresceptron learned an open number of features in each layer without supervision, where each feature is represented by a [[Convolution|convolution kernel]]. Cresceptron segmented each learned object from a cluttered scene through back-analysis through the network. [[Max pooling]], now often adopted by deep neural networks (e.g. [[ImageNet]] tests), was first used in Cresceptron to reduce the position resolution by a factor of (2x2) to 1 through the cascade for better generalization.', 44 => '', 45 => 'In 1994, André de Carvalho, together with Mike Fairhurst and David Bisset, published experimental results of a multi-layer boolean neural network, also known as a weightless neural network, composed of a 3-layers self-organising feature extraction neural network module (SOFT) followed by a multi-layer classification neural network module (GSN), which were independently trained. Each layer in the feature extraction module extracted features with growing complexity regarding the previous layer.<ref>{{Cite journal |title=An integrated Boolean neural network for pattern classification |journal=Pattern Recognition Letters |date=1994-08-08 |pages=807–813 |volume=15 |issue=8 |doi=10.1016/0167-8655(94)90009-4 |first=Andre C. L. F. |last1=de Carvalho |first2 = Mike C. |last2=Fairhurst |first3=David |last3 = Bisset}}</ref>', 46 => '', 47 => 'In 1995, [[Brendan Frey]] demonstrated that it was possible to train (over two days) a network containing six fully connected layers and several hundred hidden units using the [[wake-sleep algorithm]], co-developed with [[Peter Dayan]] and [[Geoffrey Hinton|Hinton]].<ref>{{Cite journal|title = The wake-sleep algorithm for unsupervised neural networks |journal = Science|date = 1995-05-26|pages = 1158–1161|volume = 268|issue = 5214|doi = 10.1126/science.7761831|pmid = 7761831|first = Geoffrey E.|last = Hinton|first2 = Peter|last2 = Dayan|first3 = Brendan J.|last3 = Frey|first4 = Radford|last4 = Neal|bibcode = 1995Sci...268.1158H}}</ref> Many factors contribute to the slow speed, including the [[vanishing gradient problem]] analyzed in 1991 by [[Sepp Hochreiter]].<ref name="HOCH1991">S. Hochreiter., "[http://people.idsia.ch/~juergen/SeppHochreiter1991ThesisAdvisorSchmidhuber.pdf Untersuchungen zu dynamischen neuronalen Netzen]," ''Diploma thesis. Institut f. Informatik, Technische Univ. Munich. Advisor: J. Schmidhuber'', 1991.</ref><ref name="HOCH2001">{{cite book|chapter-url={{google books |plainurl=y |id=NWOcMVA64aAC}}|title=A Field Guide to Dynamical Recurrent Networks|last=Hochreiter|first=S.|display-authors=etal|date=15 January 2001|publisher=John Wiley & Sons|isbn=978-0-7803-5369-5|location=|pages=|chapter=Gradient flow in recurrent nets: the difficulty of learning long-term dependencies|editor-last2=Kremer|editor-first2=Stefan C.|editor-first1=John F.|editor-last1=Kolen}}</ref>', 48 => '', 49 => 'Simpler models that use task-specific handcrafted features such as [[Gabor filter]]s and [[support vector machine]]s (SVMs) were a popular choice in the 1990s and 2000s, because of [[artificial neural network]]'s (ANN) computational cost and a lack of understanding of how the brain wires its biological networks.', 50 => '', 51 => 'Both shallow and deep learning (e.g., recurrent nets) of ANNs have been explored for many years.<ref>{{Cite journal|last=Morgan|first=Nelson|last2=Bourlard |first2=Hervé |last3=Renals |first3=Steve |last4=Cohen |first4=Michael|last5=Franco |first5=Horacio |date=1993-08-01 |title=Hybrid neural network/hidden markov model systems for continuous speech recognition |journal=International Journal of Pattern Recognition and Artificial Intelligence|volume=07|issue=4|pages=899–916|doi=10.1142/s0218001493000455|issn=0218-0014}}</ref><ref name="Robinson1992">{{Cite journal|last=Robinson|first=T.|authorlink=Tony Robinson (speech recognition)|date=1992|title=A real-time recurrent error propagation network word recognition system|url=http://dl.acm.org/citation.cfm?id=1895720|journal=ICASSP|pages=617–620|via=|isbn=9780780305328|series=Icassp'92}}</ref><ref>{{Cite journal|last=Waibel|first=A.|last2=Hanazawa|first2=T.|last3=Hinton|first3=G.|last4=Shikano|first4=K.|last5=Lang|first5=K. J.|date=March 1989|title=Phoneme recognition using time-delay neural networks|journal=IEEE Transactions on Acoustics, Speech, and Signal Processing|volume=37|issue=3|pages=328–339|doi=10.1109/29.21701|issn=0096-3518|hdl=10338.dmlcz/135496|url=http://dml.cz/bitstream/handle/10338.dmlcz/135496/Kybernetika_38-2002-6_2.pdf}}</ref> These methods never outperformed non-uniform internal-handcrafting Gaussian [[mixture model]]/[[Hidden Markov model]] (GMM-HMM) technology based on generative models of speech trained discriminatively.<ref name="Baker2009">{{cite journal | last1 = Baker | first1 = J. | last2 = Deng | first2 = Li | last3 = Glass | first3 = Jim | last4 = Khudanpur | first4 = S. | last5 = Lee | first5 = C.-H. | last6 = Morgan | first6 = N. | last7 = O'Shaughnessy | first7 = D. | year = 2009 | title = Research Developments and Directions in Speech Recognition and Understanding, Part 1 | url= | journal = IEEE Signal Processing Magazine | volume = 26 | issue = 3| pages = 75–80 | doi=10.1109/msp.2009.932166| bibcode = 2009ISPM...26...75B }}</ref> Key difficulties have been analyzed, including gradient diminishing<ref name="HOCH1991" /> and weak temporal correlation structure in neural predictive models.<ref name="Bengio1991">{{Cite web|url=https://www.researchgate.net/publication/41229141|title=Artificial Neural Networks and their Application to Speech/Sequence Recognition|last=Bengio|first=Y.|date=1991|website=|publisher=McGill University Ph.D. thesis|accessdate=}}</ref><ref name="Deng1994">{{cite journal | last1 = Deng | first1 = L. | last2 = Hassanein | first2 = K. | last3 = Elmasry | first3 = M. | year = 1994 | title = Analysis of correlation structure for a neural predictive model with applications to speech recognition | url= | journal = Neural Networks | volume = 7 | issue = 2| pages = 331–339 | doi=10.1016/0893-6080(94)90027-2}}</ref> Additional difficulties were the lack of training data and limited computing power.', 52 => '', 53 => 'Most [[speech recognition]] researchers moved away from neural nets to pursue generative modeling. An exception was at [[SRI International]] in the late 1990s. Funded by the US government's [[National Security Agency|NSA]] and [[DARPA]], SRI studied deep neural networks in speech and speaker recognition. The speaker recognition team led by [[Larry Heck]] reported significant success with deep neural networks in speech processing in the 1998 [[National Institute of Standards and Technology]] Speaker Recognition evaluation.<ref name="Doddington2000">{{cite journal | last1 = Doddington | first1 = G. | last2 = Przybocki | first2 = M. | last3 = Martin | first3 = A. | last4 = Reynolds | first4 = D. | year = 2000 | title = The NIST speaker recognition evaluation ± Overview, methodology, systems, results, perspective | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 225–254 | doi=10.1016/S0167-6393(99)00080-1}}</ref> The SRI deep neural network was then deployed in the Nuance Verifier, representing the first major industrial application of deep learning.<ref name="Heck2000">{{cite journal | last1 = Heck | first1 = L. | last2 = Konig | first2 = Y. | last3 = Sonmez | first3 = M. | last4 = Weintraub | first4 = M. | year = 2000 | title = Robustness to Telephone Handset Distortion in Speaker Recognition by Discriminative Feature Design | url= | journal = Speech Communication | volume = 31 | issue = 2| pages = 181–192 | doi=10.1016/s0167-6393(99)00077-1}}</ref>', 54 => '', 55 => 'The principle of elevating "raw" features over hand-crafted optimization was first explored successfully in the architecture of deep autoencoder on the "raw" spectrogram or linear filter-bank features in the late 1990s,<ref name="Heck2000" /> showing its superiority over the Mel-Cepstral features that contain stages of fixed transformation from spectrograms. The raw features of speech, [[waveform]]s, later produced excellent larger-scale results.<ref>{{Cite web|url=https://www.researchgate.net/publication/266030526|title=Acoustic Modeling with Deep Neural Networks Using Raw Time Signal for LVCSR (PDF Download Available)|website=ResearchGate|accessdate=2017-06-14}}</ref>', 56 => '', 57 => 'Many aspects of speech recognition were taken over by a deep learning method called [[long short-term memory]] (LSTM), a recurrent neural network published by Hochreiter and [[Jürgen Schmidhuber|Schmidhuber]] in 1997.<ref name=":0">{{Cite journal|last=Hochreiter|first=Sepp|last2=Schmidhuber|first2=Jürgen|date=1997-11-01|title=Long Short-Term Memory|journal=Neural Computation|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|issn=0899-7667|pmid=9377276|url=https://www.semanticscholar.org/paper/44d2abe2175df8153f465f6c39b68b76a0d40ab9}}</ref> LSTM RNNs avoid the vanishing gradient problem and can learn "Very Deep Learning" tasks<ref name="SCHIDHUB" /> that require memories of events that happened thousands of discrete time steps before, which is important for speech. In 2003, LSTM started to become competitive with traditional speech recognizers on certain tasks.<ref name="graves2003">{{Cite web|url=Ftp://ftp.idsia.ch/pub/juergen/bioadit2004.pdf|title=Biologically Plausible Speech Recognition with LSTM Neural Nets|last=Graves|first=Alex|last2=Eck|first2=Douglas|date=2003|website=1st Intl. Workshop on Biologically Inspired Approaches to Advanced Information Technology, Bio-ADIT 2004, Lausanne, Switzerland|pages=175–184|last3=Beringer|first3=Nicole|last4=Schmidhuber|first4=Jürgen}}</ref> Later it was combined with connectionist temporal classification (CTC)<ref name=":1">{{Cite journal|last=Graves|first=Alex|last2=Fernández|first2=Santiago|last3=Gomez|first3=Faustino|date=2006|title=Connectionist temporal classification: Labelling unsegmented sequence data with recurrent neural networks|journal=Proceedings of the International Conference on Machine Learning, ICML 2006|pages=369–376|citeseerx=10.1.1.75.6306}}</ref> in stacks of LSTM RNNs.<ref name="fernandez2007keyword">Santiago Fernandez, Alex Graves, and Jürgen Schmidhuber (2007). [https://mediatum.ub.tum.de/doc/1289941/file.pdf An application of recurrent neural networks to discriminative keyword spotting]. Proceedings of ICANN (2), pp. 220–229.</ref> In 2015, Google's speech recognition reportedly experienced a dramatic performance jump of 49% through CTC-trained LSTM, which they made available through [[Google Voice Search]].<ref name="sak2015">{{Cite web|url=http://googleresearch.blogspot.ch/2015/09/google-voice-search-faster-and-more.html|title=Google voice search: faster and more accurate|last=Sak|first=Haşim|last2=Senior|first2=Andrew|date=September 2015|website=|accessdate=|last3=Rao|first3=Kanishka|last4=Beaufays|first4=Françoise|last5=Schalkwyk|first5=Johan}}</ref>', 58 => '', 59 => 'In 2006, publications by [[Geoffrey Hinton|Geoff Hinton]], [[Russ Salakhutdinov|Ruslan Salakhutdinov]], Osindero and [[Yee Whye Teh|Teh]]<ref>{{Cite journal|last=Hinton|first=Geoffrey E.|date=2007-10-01|title=Learning multiple layers of representation|url=http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613(07)00217-3|journal=Trends in Cognitive Sciences|volume=11|issue=10|pages=428–434|doi=10.1016/j.tics.2007.09.004|issn=1364-6613|pmid=17921042}}</ref>', 60 => '<ref name=hinton06>{{Cite journal | last1 = Hinton | first1 = G. E. |authorlink1=Geoff Hinton| last2 = Osindero | first2 = S. | last3 = Teh | first3 = Y. W. | doi = 10.1162/neco.2006.18.7.1527 | title = A Fast Learning Algorithm for Deep Belief Nets | journal = [[Neural Computation (journal)|Neural Computation]]| volume = 18 | issue = 7 | pages = 1527–1554 | year = 2006 | pmid = 16764513| pmc = | url = http://www.cs.toronto.edu/~hinton/absps/fastnc.pdf}}</ref><ref name=bengio2012>{{cite arXiv |last=Bengio |first=Yoshua |author-link=Yoshua Bengio |eprint=1206.5533 |title=Practical recommendations for gradient-based training of deep architectures |class=cs.LG|year=2012 }}</ref> showed how a many-layered [[feedforward neural network]] could be effectively pre-trained one layer at a time, treating each layer in turn as an unsupervised [[restricted Boltzmann machine]], then fine-tuning it using supervised [[backpropagation]].<ref name="HINTON2007">G. E. Hinton., "[http://www.csri.utoronto.ca/~hinton/absps/ticsdraft.pdf Learning multiple layers of representation]," ''Trends in Cognitive Sciences'', 11, pp. 428–434, 2007.</ref> The papers referred to ''learning'' for ''deep belief nets.''', 61 => '', 62 => 'Deep learning is part of state-of-the-art systems in various disciplines, particularly computer vision and [[automatic speech recognition]] (ASR). Results on commonly used evaluation sets such as [[TIMIT]] (ASR) and [[MNIST database|MNIST]] ([[image classification]]), as well as a range of large-vocabulary speech recognition tasks have steadily improved.<ref name="HintonDengYu2012" /><ref>{{cite journal|url=https://www.microsoft.com/en-us/research/publication/new-types-of-deep-neural-network-learning-for-speech-recognition-and-related-applications-an-overview/|title=New types of deep neural network learning for speech recognition and related applications: An overview|journal=Microsoft Research|first1=Li|last1=Deng|first2=Geoffrey|last2=Hinton|first3=Brian|last3=Kingsbury|date=1 May 2013|via=research.microsoft.com|citeseerx=10.1.1.368.1123}}</ref><ref>{{Cite book |doi=10.1109/icassp.2013.6639345|isbn=978-1-4799-0356-6|chapter=Recent advances in deep learning for speech research at Microsoft|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8604–8608|year=2013|last1=Deng|first1=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Michael|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|last10=Williams|first10=Jason|last11=Gong|first11=Yifan|last12=Acero|first12=Alex}}</ref> [[Convolutional neural network]]s (CNNs) were superseded for ASR by CTC<ref name=":1" /> for LSTM.<ref name=":0" /><ref name="sak2015" /><ref name="sak2014">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|title=Long Short-Term Memory recurrent neural network architectures for large scale acoustic modeling|last=Sak|first=Hasim|last2=Senior|first2=Andrew|date=2014|website=|accessdate=|last3=Beaufays|first3=Francoise|archive-url=https://web.archive.org/web/20180424203806/https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43905.pdf|archive-date=2018-04-24|url-status=dead}}</ref><ref name="liwu2015">{{cite arxiv |eprint=1410.4281|last1=Li|first1=Xiangang|title=Constructing Long Short-Term Memory based Deep Recurrent Neural Networks for Large Vocabulary Speech Recognition|last2=Wu|first2=Xihong|class=cs.CL|year=2014}}</ref><ref name="zen2015">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=Unidirectional Long Short-Term Memory Recurrent Neural Network with Recurrent Output Layer for Low-Latency Speech Synthesis|last=Zen|first=Heiga|last2=Sak|first2=Hasim|date=2015|website=Google.com|publisher=ICASSP|pages=4470–4474|accessdate=}}</ref><ref name="CNNspeech2013">{{Cite web|url=https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/43266.pdf|title=A deep convolutional neural network using heterogeneous pooling for trading acoustic invariance with phonetic confusion|last=Deng|first=L.|last2=Abdel-Hamid|first2=O.|date=2013|website=Google.com|publisher=ICASSP|accessdate=|last3=Yu|first3=D.}}</ref><ref name=":2">{{Cite book |doi=10.1109/icassp.2013.6639347|isbn=978-1-4799-0356-6|chapter=Deep convolutional neural networks for LVCSR|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8614–8618|year=2013|last1=Sainath|first1=Tara N.|last2=Mohamed|first2=Abdel-Rahman|last3=Kingsbury|first3=Brian|last4=Ramabhadran|first4=Bhuvana}}</ref> but are more successful in computer vision.', 63 => '', 64 => 'The impact of deep learning in industry began in the early 2000s, when CNNs already processed an estimated 10% to 20% of all the checks written in the US, according to Yann LeCun.<ref name="lecun2016slides">[[Yann LeCun]] (2016). Slides on Deep Learning [https://indico.cern.ch/event/510372/ Online]</ref> Industrial applications of deep learning to large-scale speech recognition started around 2010.', 65 => '', 66 => 'The 2009 NIPS Workshop on Deep Learning for Speech Recognition<ref name="NIPS2009" /> was motivated by the limitations of deep generative models of speech, and the possibility that given more capable hardware and large-scale data sets that deep neural nets (DNN) might become practical. It was believed that pre-training DNNs using generative models of deep belief nets (DBN) would overcome the main difficulties of neural nets.<ref name="HintonKeynoteICASSP2013" /> However, it was discovered that replacing pre-training with large amounts of training data for straightforward backpropagation when using DNNs with large, context-dependent output layers produced error rates dramatically lower than then-state-of-the-art Gaussian mixture model (GMM)/Hidden Markov Model (HMM) and also than more-advanced generative model-based systems.<ref name="HintonDengYu2012">{{cite journal | last1 = Hinton | first1 = G. | last2 = Deng | first2 = L. | last3 = Yu | first3 = D. | last4 = Dahl | first4 = G. | last5 = Mohamed | first5 = A. | last6 = Jaitly | first6 = N. | last7 = Senior | first7 = A. | last8 = Vanhoucke | first8 = V. | last9 = Nguyen | first9 = P. | last10 = Sainath | first10 = T. | last11 = Kingsbury | first11 = B. | year = 2012 | title = Deep Neural Networks for Acoustic Modeling in Speech Recognition: The Shared Views of Four Research Groups| url= | journal = IEEE Signal Processing Magazine | volume = 29 | issue = 6| pages = 82–97 | doi=10.1109/msp.2012.2205597}}</ref><ref name="patent2011">D. Yu, L. Deng, G. Li, and F. Seide (2011). "Discriminative pretraining of deep neural networks," U.S. Patent Filing.</ref> The nature of the recognition errors produced by the two types of systems was characteristically different,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009">NIPS Workshop: Deep Learning for Speech Recognition and Related Applications, Whistler, BC, Canada, Dec. 2009 (Organizers: Li Deng, Geoff Hinton, D. Yu).</ref> offering technical insights into how to integrate deep learning into the existing highly efficient, run-time speech decoding system deployed by all major speech recognition systems.<ref name="BOOK2014" /><ref name="ReferenceA">{{cite book|last2=Deng|first2=L.|date=2014|title=Automatic Speech Recognition: A Deep Learning Approach (Publisher: Springer)|url={{google books |plainurl=y |id=rUBTBQAAQBAJ}}|pages=|isbn=978-1-4471-5779-3|via=|last1=Yu|first1=D.}}</ref><ref>{{cite web|title=Deng receives prestigious IEEE Technical Achievement Award - Microsoft Research|url=https://www.microsoft.com/en-us/research/blog/deng-receives-prestigious-ieee-technical-achievement-award/|website=Microsoft Research|date=3 December 2015}}</ref> Analysis around 2009-2010, contrasted the GMM (and other generative speech models) vs. DNN models, stimulated early industrial investment in deep learning for speech recognition,<ref name="ReferenceICASSP2013" /><ref name="NIPS2009" /> eventually leading to pervasive and dominant use in that industry. That analysis was done with comparable performance (less than 1.5% in error rate) between discriminative DNNs and generative models.<ref name="HintonDengYu2012" /><ref name="ReferenceICASSP2013">{{cite journal|last2=Hinton|first2=G.|last3=Kingsbury|first3=B.|date=2013|title=New types of deep neural network learning for speech recognition and related applications: An overview (ICASSP)|url=https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/ICASSP-2013-DengHintonKingsbury-revised.pdf|journal=|pages=|via=|last1=Deng|first1=L.}}</ref><ref name="HintonKeynoteICASSP2013">Keynote talk: Recent Developments in Deep Neural Networks. ICASSP, 2013 (by Geoff Hinton).</ref><ref name="interspeech2014Keynote">{{Cite web|url=https://www.superlectures.com/interspeech2014/downloadFile?id=6&type=slides&filename=achievements-and-challenges-of-deep-learning-from-speech-analysis-and-recognition-to-language-and-multimodal-processing|title=Keynote talk: 'Achievements and Challenges of Deep Learning - From Speech Analysis and Recognition To Language and Multimodal Processing'|last=Li|first=Deng|date=September 2014|website=Interspeech|accessdate=}}</ref>', 67 => '', 68 => 'In 2010, researchers extended deep learning from TIMIT to large vocabulary speech recognition, by adopting large output layers of the DNN based on context-dependent HMM states constructed by [[decision tree]]s.<ref name="Roles2010">{{cite journal|last1=Yu|first1=D.|last2=Deng|first2=L.|date=2010|title=Roles of Pre-Training and Fine-Tuning in Context-Dependent DBN-HMMs for Real-World Speech Recognition|url=https://www.microsoft.com/en-us/research/publication/roles-of-pre-training-and-fine-tuning-in-context-dependent-dbn-hmms-for-real-world-speech-recognition/|journal=NIPS Workshop on Deep Learning and Unsupervised Feature Learning|pages=|via=}}</ref><ref>{{Cite journal|last=Seide|first=F.|last2=Li|first2=G.|last3=Yu|first3=D.|date=2011|title=Conversational speech transcription using context-dependent deep neural networks|url=https://www.microsoft.com/en-us/research/publication/conversational-speech-transcription-using-context-dependent-deep-neural-networks|journal=Interspeech|pages=|via=}}</ref><ref>{{Cite journal|last=Deng|first=Li|last2=Li|first2=Jinyu|last3=Huang|first3=Jui-Ting|last4=Yao|first4=Kaisheng|last5=Yu|first5=Dong|last6=Seide|first6=Frank|last7=Seltzer|first7=Mike|last8=Zweig|first8=Geoff|last9=He|first9=Xiaodong|date=2013-05-01|title=Recent Advances in Deep Learning for Speech Research at Microsoft|url=https://www.microsoft.com/en-us/research/publication/recent-advances-in-deep-learning-for-speech-research-at-microsoft/|journal=Microsoft Research}}</ref><ref name="ReferenceA" />', 69 => '', 70 => 'Advances in hardware have enabled renewed interest in deep learning. In 2009, [[Nvidia]] was involved in what was called the “big bang” of deep learning, “as deep-learning neural networks were trained with Nvidia [[graphics processing unit]]s (GPUs).”<ref>{{cite web|url=https://venturebeat.com/2016/04/05/nvidia-ceo-bets-big-on-deep-learning-and-vr/|title=Nvidia CEO bets big on deep learning and VR|date=April 5, 2016|publisher=[[Venture Beat]]}}</ref> That year, [[Google Brain]] used Nvidia GPUs to create capable DNNs. While there, [[Andrew Ng]] determined that GPUs could increase the speed of deep-learning systems by about 100 times.<ref>{{cite news|url=https://www.economist.com/news/special-report/21700756-artificial-intelligence-boom-based-old-idea-modern-twist-not|title=From not working to neural networking|newspaper=[[The Economist]]}}</ref> In particular, GPUs are well-suited for the matrix/vector computations involved in machine learning.<ref name="jung2004">{{cite journal | last1 = Oh | first1 = K.-S. | last2 = Jung | first2 = K. | year = 2004 | title = GPU implementation of neural networks | url= | journal = Pattern Recognition | volume = 37 | issue = 6| pages = 1311–1314 | doi=10.1016/j.patcog.2004.01.013}}</ref><ref>"[https://www.academia.edu/40135801 A Survey of Techniques for Optimizing Deep Learning on GPUs]", S. Mittal and S. Vaishay, Journal of Systems Architecture, 2019</ref><ref name="chellapilla2006">Chellapilla, K., Puri, S., and Simard, P. (2006). High performance convolutional neural networks for document processing. International Workshop on Frontiers in Handwriting Recognition.</ref> GPUs speed up training algorithms by orders of magnitude, reducing running times from weeks to days.<ref name=":3">{{Cite journal|last=Cireşan|first=Dan Claudiu|last2=Meier|first2=Ueli|last3=Gambardella|first3=Luca Maria|last4=Schmidhuber|first4=Jürgen|date=2010-09-21|title=Deep, Big, Simple Neural Nets for Handwritten Digit Recognition|journal=Neural Computation|volume=22|issue=12|pages=3207–3220|doi=10.1162/neco_a_00052|pmid=20858131|issn=0899-7667|arxiv=1003.0358}}</ref><ref>{{Cite journal|last=Raina|first=Rajat|last2=Madhavan|first2=Anand|last3=Ng|first3=Andrew Y.|date=2009|title=Large-scale Deep Unsupervised Learning Using Graphics Processors|journal=Proceedings of the 26th Annual International Conference on Machine Learning|series=ICML '09|location=New York, NY, USA|publisher=ACM|pages=873–880|doi=10.1145/1553374.1553486|isbn=9781605585161|citeseerx=10.1.1.154.372|url=https://www.semanticscholar.org/paper/e337c5e4c23999c36f64bcb33ebe6b284e1bcbf1}}</ref> Further, specialized hardware and algorithm optimizations can be used for efficient processing of deep learning models.<ref name="sze2017">{{cite arXiv', 71 => '|title= Efficient Processing of Deep Neural Networks: A Tutorial and Survey', 72 => '|last1=Sze |first1=Vivienne', 73 => '|last2=Chen |first2=Yu-Hsin', 74 => '|last3=Yang |first3=Tien-Ju', 75 => '|last4=Emer |first4=Joel', 76 => '|eprint=1703.09039', 77 => '|year=2017', 78 => '|class=cs.CV }}</ref>', 79 => '', 80 => '=== Deep learning revolution ===', 81 => '[[File:AI-ML-DL.png|thumb|How deep learning is a subset of machine learning and how machine learning is a subset of artificial intelligence (AI).]]', 82 => 'In 2012, a team led by George E. Dahl won the "Merck Molecular Activity Challenge" using multi-task deep neural networks to predict the [[biomolecular target]] of one drug.<ref name="MERCK2012">{{cite web|url=https://www.kaggle.com/c/MerckActivity/details/winners|title=Announcement of the winners of the Merck Molecular Activity Challenge}}</ref><ref name=":5">{{Cite web|url=http://www.datascienceassn.org/content/multi-task-neural-networks-qsar-predictions|title=Multi-task Neural Networks for QSAR Predictions {{!}} Data Science Association|website=www.datascienceassn.org|accessdate=2017-06-14}}</ref> In 2014, Hochreiter's group used deep learning to detect off-target and toxic effects of environmental chemicals in nutrients, household products and drugs and won the "Tox21 Data Challenge" of [[NIH]], [[FDA]] and [[National Center for Advancing Translational Sciences|NCATS]].<ref name="TOX21">"Toxicology in the 21st century Data Challenge"</ref><ref name="TOX21Data">{{cite web|url=https://tripod.nih.gov/tox21/challenge/leaderboard.jsp|title=NCATS Announces Tox21 Data Challenge Winners}}</ref><ref name=":11">{{cite web|url=http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|title=Archived copy|archiveurl=https://web.archive.org/web/20150228225709/http://www.ncats.nih.gov/news-and-events/features/tox21-challenge-winners.html|archivedate=2015-02-28|url-status=dead|accessdate=2015-03-05}}</ref>', 83 => '', 84 => 'Significant additional impacts in image or object recognition were felt from 2011 to 2012. Although CNNs trained by backpropagation had been around for decades, and GPU implementations of NNs for years, including CNNs, fast implementations of CNNs with max-pooling on GPUs in the style of Ciresan and colleagues were needed to progress on computer vision.<ref name="jung2004" /><ref name="chellapilla2006" /><ref name="LECUN1989" /><ref name=":6">{{Cite journal|last=Ciresan|first=D. C.|last2=Meier|first2=U.|last3=Masci|first3=J.|last4=Gambardella|first4=L. M.|last5=Schmidhuber|first5=J.|date=2011|title=Flexible, High Performance Convolutional Neural Networks for Image Classification|url=http://ijcai.org/papers11/Papers/IJCAI11-210.pdf|journal=International Joint Conference on Artificial Intelligence|pages=|doi=10.5591/978-1-57735-516-8/ijcai11-210|via=}}</ref><ref name="SCHIDHUB" /> In 2011, this approach achieved for the first time superhuman performance in a visual pattern recognition contest. Also in 2011, it won the ICDAR Chinese handwriting contest, and in May 2012, it won the ISBI image segmentation contest.<ref name=":8">{{Cite book|url=http://papers.nips.cc/paper/4741-deep-neural-networks-segment-neuronal-membranes-in-electron-microscopy-images.pdf|title=Advances in Neural Information Processing Systems 25|last=Ciresan|first=Dan|last2=Giusti|first2=Alessandro|last3=Gambardella|first3=Luca M.|last4=Schmidhuber|first4=Juergen|date=2012|publisher=Curran Associates, Inc.|editor-last=Pereira|editor-first=F.|pages=2843–2851|editor-last2=Burges|editor-first2=C. J. C.|editor-last3=Bottou|editor-first3=L.|editor-last4=Weinberger|editor-first4=K. Q.}}</ref> Until 2011, CNNs did not play a major role at computer vision conferences, but in June 2012, a paper by Ciresan et al. at the leading conference CVPR<ref name=":9" /> showed how max-pooling CNNs on GPU can dramatically improve many vision benchmark records. In October 2012, a similar system by Krizhevsky et al.<ref name="krizhevsky2012" /> won the large-scale [[ImageNet competition]] by a significant margin over shallow machine learning methods. In November 2012, Ciresan et al.'s system also won the ICPR contest on analysis of large medical images for cancer detection, and in the following year also the MICCAI Grand Challenge on the same topic.<ref name="ciresan2013miccai">{{Cite journal|last=Ciresan|first=D.|last2=Giusti|first2=A.|last3=Gambardella|first3=L.M.|last4=Schmidhuber|first4=J.|date=2013|title=Mitosis Detection in Breast Cancer Histology Images using Deep Neural Networks|journal=Proceedings MICCAI|volume=7908|issue=Pt 2|pages=411–418|doi=10.1007/978-3-642-40763-5_51|pmid=24579167|series=Lecture Notes in Computer Science|isbn=978-3-642-38708-1}}</ref> In 2013 and 2014, the error rate on the ImageNet task using deep learning was further reduced, following a similar trend in large-scale speech recognition. The [[Stephen Wolfram|Wolfram]] Image Identification project publicized these improvements.<ref>{{Cite web|url=https://www.imageidentify.com/|title=The Wolfram Language Image Identification Project|website=www.imageidentify.com|accessdate=2017-03-22}}</ref>', 85 => '', 86 => 'Image classification was then extended to the more challenging task of [[Automatic image annotation|generating descriptions]] (captions) for images, often as a combination of CNNs and LSTMs.<ref name="1411.4555">{{cite arxiv |eprint=1411.4555|last1=Vinyals|first1=Oriol|title=Show and Tell: A Neural Image Caption Generator|last2=Toshev|first2=Alexander|last3=Bengio|first3=Samy|last4=Erhan|first4=Dumitru|class=cs.CV|year=2014}}.</ref><ref name="1411.4952">{{cite arxiv |eprint=1411.4952|last1=Fang|first1=Hao|title=From Captions to Visual Concepts and Back|last2=Gupta|first2=Saurabh|last3=Iandola|first3=Forrest|last4=Srivastava|first4=Rupesh|last5=Deng|first5=Li|last6=Dollár|first6=Piotr|last7=Gao|first7=Jianfeng|last8=He|first8=Xiaodong|last9=Mitchell|first9=Margaret|last10=Platt|first10=John C|last11=Lawrence Zitnick|first11=C|last12=Zweig|first12=Geoffrey|class=cs.CV|year=2014}}.</ref><ref name="1411.2539">{{cite arxiv |eprint=1411.2539|last1=Kiros|first1=Ryan|title=Unifying Visual-Semantic Embeddings with Multimodal Neural Language Models|last2=Salakhutdinov|first2=Ruslan|last3=Zemel|first3=Richard S|class=cs.LG|year=2014}}.</ref><ref>{{Cite journal|last=Zhong|first=Sheng-hua|last2=Liu|first2=Yan|last3=Liu|first3=Yang|date=2011|title=Bilinear Deep Learning for Image Classification|journal=Proceedings of the 19th ACM International Conference on Multimedia|series=MM '11|location=New York, NY, USA|publisher=ACM|pages=343–352|doi=10.1145/2072298.2072344|isbn=9781450306164|url=https://www.semanticscholar.org/paper/e1bbfb2c7ef74445b4fad9199b727464129df582}}</ref>', 87 => '', 88 => 'Some researchers assess that the October 2012 ImageNet victory anchored the start of a "deep learning revolution" that has transformed the AI industry.<ref>{{cite news|title=Why Deep Learning Is Suddenly Changing Your Life|url=http://fortune.com/ai-artificial-intelligence-deep-machine-learning/|accessdate=13 April 2018|work=Fortune|date=2016}}</ref>', 89 => '', 90 => 'In March 2019, [[Yoshua Bengio]], [[Geoffrey Hinton]] and [[Yann LeCun]] were awarded the [[Turing Award]] for conceptual and engineering breakthroughs that have made deep neural networks a critical component of computing.', 91 => '', 92 => '== Neural networks ==', 93 => '', 94 => '=== Artificial neural networks ===', 95 => '{{Main|Artificial neural network}}', 96 => ''''Artificial neural networks''' ('''ANNs''') or '''[[Connectionism|connectionist]] systems''' are computing systems inspired by the [[biological neural network]]s that constitute animal brains. Such systems learn (progressively improve their ability) to do tasks by considering examples, generally without task-specific programming. For example, in image recognition, they might learn to identify images that contain cats by analyzing example images that have been manually [[Labeled data|labeled]] as "cat" or "no cat" and using the analytic results to identify cats in other images. They have found most use in applications difficult to express with a traditional computer algorithm using [[rule-based programming]].', 97 => '', 98 => 'An ANN is based on a collection of connected units called [[artificial neuron]]s, (analogous to biological neurons in a [[Brain|biological brain]]). Each connection ([[synapse]]) between neurons can transmit a signal to another neuron. The receiving (postsynaptic) neuron can process the signal(s) and then signal downstream neurons connected to it. Neurons may have state, generally represented by [[real numbers]], typically between 0 and 1. Neurons and synapses may also have a weight that varies as learning proceeds, which can increase or decrease the strength of the signal that it sends downstream.', 99 => '', 100 => 'Typically, neurons are organized in layers. Different layers may perform different kinds of transformations on their inputs. Signals travel from the first (input), to the last (output) layer, possibly after traversing the layers multiple times.', 101 => '', 102 => 'The original goal of the neural network approach was to solve problems in the same way that a human brain would. Over time, attention focused on matching specific mental abilities, leading to deviations from biology such as backpropagation, or passing information in the reverse direction and adjusting the network to reflect that information.', 103 => '', 104 => 'Neural networks have been used on a variety of tasks, including computer vision, [[speech recognition]], [[machine translation]], [[social network]] filtering, [[general game playing|playing board and video games]] and medical diagnosis.', 105 => '', 106 => 'As of 2017, neural networks typically have a few thousand to a few million units and millions of connections. Despite this number being several order of magnitude less than the number of neurons on a human brain, these networks can perform many tasks at a level beyond that of humans (e.g., recognizing faces, playing "Go"<ref>{{Cite journal|last=Silver|first=David|last2=Huang|first2=Aja|last3=Maddison|first3=Chris J.|last4=Guez|first4=Arthur|last5=Sifre|first5=Laurent|last6=Driessche|first6=George van den|last7=Schrittwieser|first7=Julian|last8=Antonoglou|first8=Ioannis|last9=Panneershelvam|first9=Veda|date=January 2016|title=Mastering the game of Go with deep neural networks and tree search|journal=Nature|volume=529|issue=7587|pages=484–489|doi=10.1038/nature16961|issn=1476-4687|pmid=26819042|bibcode=2016Natur.529..484S|url=https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}</ref> ).', 107 => '', 108 => '=== Deep neural networks ===', 109 => '{{technical|section|date=July 2016}}', 110 => 'A deep neural network (DNN) is an [[artificial neural network]] (ANN) with multiple layers between the input and output layers.<ref name="BENGIODEEP" /><ref name="SCHIDHUB" /> The DNN finds the correct mathematical manipulation to turn the input into the output, whether it be a [[linear relationship]] or a non-linear relationship. The network moves through the layers calculating the probability of each output. For example, a DNN that is trained to recognize dog breeds will go over the given image and calculate the probability that the dog in the image is a certain breed. The user can review the results and select which probabilities the network should display (above a certain threshold, etc.) and return the proposed label. Each mathematical manipulation as such is considered a layer, and complex DNN have many layers, hence the name "deep" networks.', 111 => '', 112 => 'DNNs can model complex non-linear relationships. DNN architectures generate compositional models where the object is expressed as a layered composition of [[Primitive data type|primitives]].<ref>{{Cite journal|last=Szegedy|first=Christian|last2=Toshev|first2=Alexander|last3=Erhan|first3=Dumitru|date=2013|title=Deep neural networks for object detection|url=https://papers.nips.cc/paper/5207-deep-neural-networks-for-object-detection|journal=Advances in Neural Information Processing Systems|pages=2553–2561|via=}}</ref> The extra layers enable composition of features from lower layers, potentially modeling complex data with fewer units than a similarly performing shallow network.<ref name="BENGIODEEP" />', 113 => '', 114 => 'Deep architectures include many variants of a few basic approaches. Each architecture has found success in specific domains. It is not always possible to compare the performance of multiple architectures, unless they have been evaluated on the same data sets.', 115 => '', 116 => 'DNNs are typically feedforward networks in which data flows from the input layer to the output layer without looping back. At first, the DNN creates a map of virtual neurons and assigns random numerical values, or "weights", to connections between them. The weights and inputs are multiplied and return an output between 0 and 1. If the network did not accurately recognize a particular pattern, an algorithm would adjust the weights.<ref>{{Cite news|url=https://www.technologyreview.com/s/513696/deep-learning/|title=Is Artificial Intelligence Finally Coming into Its Own?|last=Hof|first=Robert D.|work=MIT Technology Review|access-date=2018-07-10}}</ref> That way the algorithm can make certain parameters more influential, until it determines the correct mathematical manipulation to fully process the data.', 117 => '', 118 => '[[Recurrent neural networks]] (RNNs), in which data can flow in any direction, are used for applications such as [[language model]]ing.<ref name="gers2001">{{cite journal|last1=Gers|first1=Felix A.|last2=Schmidhuber|first2=Jürgen|year=2001|title=LSTM Recurrent Networks Learn Simple Context Free and Context Sensitive Languages|url=http://elartu.tntu.edu.ua/handle/lib/30719|journal= IEEE Transactions on Neural Networks|volume=12|issue=6|pages=1333–1340|doi=10.1109/72.963769|pmid=18249962}}</ref><ref name="NIPS2014"/><ref name="vinyals2016">{{cite arxiv |eprint=1602.02410|last1=Jozefowicz|first1=Rafal|title=Exploring the Limits of Language Modeling|last2=Vinyals|first2=Oriol|last3=Schuster|first3=Mike|last4=Shazeer|first4=Noam|last5=Wu|first5=Yonghui|class=cs.CL|year=2016}}</ref><ref name="gillick2015">{{cite arxiv |eprint=1512.00103|last1=Gillick|first1=Dan|title=Multilingual Language Processing from Bytes|last2=Brunk|first2=Cliff|last3=Vinyals|first3=Oriol|last4=Subramanya|first4=Amarnag|class=cs.CL|year=2015}}</ref><ref name="MIKO2010">{{Cite journal|last=Mikolov|first=T.|display-authors=etal|date=2010|title=Recurrent neural network based language model|url=http://www.fit.vutbr.cz/research/groups/speech/servite/2010/rnnlm_mikolov.pdf|journal=Interspeech|pages=|via=}}</ref> Long short-term memory is particularly effective for this use.<ref name=":0" /><ref name=":10">{{Cite web|url=https://www.researchgate.net/publication/220320057|title=Learning Precise Timing with LSTM Recurrent Networks (PDF Download Available)|website=ResearchGate|accessdate=2017-06-13}}</ref>', 119 => '', 120 => '[[Convolutional neural network|Convolutional deep neural networks (CNNs)]] are used in computer vision.<ref name="LECUN86">{{cite journal |last1=LeCun |first1=Y. |display-authors=etal |year= 1998|title=Gradient-based learning applied to document recognition |url= |journal=Proceedings of the IEEE |volume=86 |issue=11 |pages=2278–2324 |doi=10.1109/5.726791}}</ref> CNNs also have been applied to [[acoustic model]]ing for automatic speech recognition (ASR).<ref name=":2" />', 121 => '', 122 => '==== Challenges ====', 123 => 'As with ANNs, many issues can arise with naively trained DNNs. Two common issues are [[overfitting]] and computation time.', 124 => '', 125 => 'DNNs are prone to overfitting because of the added layers of abstraction, which allow them to model rare dependencies in the training data. [[Regularization (mathematics)|Regularization]] methods such as Ivakhnenko's unit pruning<ref name="ivak1971"/> or [[weight decay]] (<math> \ell_2 </math>-regularization) or [[sparse matrix|sparsity]] (<math> \ell_1 </math>-regularization) can be applied during training to combat overfitting.<ref>{{Cite book |doi=10.1109/icassp.2013.6639349|isbn=978-1-4799-0356-6|arxiv=1212.0901|citeseerx=10.1.1.752.9151|chapter=Advances in optimizing recurrent networks|title=2013 IEEE International Conference on Acoustics, Speech and Signal Processing|pages=8624–8628|year=2013|last1=Bengio|first1=Yoshua|last2=Boulanger-Lewandowski|first2=Nicolas|last3=Pascanu|first3=Razvan}}</ref> Alternatively dropout regularization randomly omits units from the hidden layers during training. This helps to exclude rare dependencies.<ref name="DAHL2013">{{Cite journal|last=Dahl|first=G.|display-authors=etal|date=2013|title=Improving DNNs for LVCSR using rectified linear units and dropout|url=http://www.cs.toronto.edu/~gdahl/papers/reluDropoutBN_icassp2013.pdf|journal=ICASSP|pages=|via=}}</ref> Finally, data can be augmented via methods such as cropping and rotating such that smaller training sets can be increased in size to reduce the chances of overfitting.<ref>{{Cite web|url=https://www.coursera.org/learn/convolutional-neural-networks/lecture/AYzbX/data-augmentation|title=Data Augmentation - deeplearning.ai {{!}} Coursera|website=Coursera|accessdate=2017-11-30}}</ref>', 126 => '', 127 => 'DNNs must consider many training parameters, such as the size (number of layers and number of units per layer), the [[learning rate]], and initial weights. [[Hyperparameter optimization#Grid search|Sweeping through the parameter space]] for optimal parameters may not be feasible due to the cost in time and computational resources. Various tricks, such as batching (computing the gradient on several training examples at once rather than individual examples)<ref name="RBMTRAIN">{{Cite journal|last=Hinton|first=G. E.|date=2010|title=A Practical Guide to Training Restricted Boltzmann Machines|url=https://www.researchgate.net/publication/221166159|journal=Tech. Rep. UTML TR 2010-003|pages=|via=}}</ref> speed up computation. Large processing capabilities of many-core architectures (such as GPUs or the Intel Xeon Phi) have produced significant speedups in training, because of the suitability of such processing architectures for the matrix and vector computations.<ref>{{cite book|last1=You|first1=Yang|title=Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis on - SC '17|pages=1–12|last2=Buluç|first2=Aydın|last3=Demmel|first3=James|chapter=Scaling deep learning on GPU and knights landing clusters|chapter-url=https://dl.acm.org/citation.cfm?doid=3126908.3126912|publisher=SC '17, ACM|date=November 2017|accessdate=5 March 2018|doi=10.1145/3126908.3126912|isbn=9781450351140|url=http://www.escholarship.org/uc/item/6ch40821}}</ref><ref>{{cite journal|last1=Viebke|first1=André|last2=Memeti|first2=Suejb|last3=Pllana|first3=Sabri|last4=Abraham|first4=Ajith|title=CHAOS: a parallelization scheme for training convolutional neural networks on Intel Xeon Phi|journal=The Journal of Supercomputing|volume=75|pages=197–227|doi=10.1007/s11227-017-1994-x|accessdate=|arxiv=1702.07908|bibcode=2017arXiv170207908V|url=https://www.semanticscholar.org/paper/aa8a4d2de94cc0a8ccff21f651c005613e8ec0e8|year=2019}}</ref>', 128 => '', 129 => 'Alternatively, engineers may look for other types of neural networks with more straightforward and convergent training algorithms. CMAC ([[cerebellar model articulation controller]]) is one such kind of neural network. It doesn't require learning rates or randomized initial weights for CMAC. The training process can be guaranteed to converge in one step with a new batch of data, and the computational complexity of the training algorithm is linear with respect to the number of neurons involved.<ref name=Qin1>Ting Qin, et al. "A learning algorithm of CMAC based on RLS." Neural Processing Letters 19.1 (2004): 49-61.</ref><ref name=Qin2>Ting Qin, et al. "[http://www-control.eng.cam.ac.uk/Homepage/papers/cued_control_997.pdf Continuous CMAC-QRLS and its systolic array]." Neural Processing Letters 22.1 (2005): 1-16.</ref>', 130 => '', 131 => '== Applications ==', 132 => '', 133 => '=== Automatic speech recognition ===', 134 => '{{Main|Speech recognition}}', 135 => '', 136 => 'Large-scale automatic speech recognition is the first and most convincing successful case of deep learning. LSTM RNNs can learn "Very Deep Learning" tasks<ref name="SCHIDHUB"/> that involve multi-second intervals containing speech events separated by thousands of discrete time steps, where one time step corresponds to about 10 ms. LSTM with forget gates<ref name=":10" /> is competitive with traditional speech recognizers on certain tasks.<ref name="graves2003"/>', 137 => '', 138 => 'The initial success in speech recognition was based on small-scale recognition tasks based on TIMIT. The data set contains 630 speakers from eight major [[dialect]]s of [[American English]], where each speaker reads 10 sentences.<ref name="LDCTIMIT">''TIMIT Acoustic-Phonetic Continuous Speech Corpus'' Linguistic Data Consortium, Philadelphia.</ref> Its small size lets many configurations be tried. More importantly, the TIMIT task concerns phone-sequence recognition, which, unlike word-sequence recognition, allows weak phone [[bigram]] language models. This lets the strength of the acoustic modeling aspects of speech recognition be more easily analyzed. The error rates listed below, including these early results and measured as percent phone error rates (PER), have been summarized since 1991.', 139 => '', 140 => '{| class="wikitable"', 141 => '|-', 142 => '! Method !! Percent phone<br>error rate (PER) (%)', 143 => '|-', 144 => '| Randomly Initialized RNN<ref>{{cite journal |last1=Robinson |first1=Tony |authorlink=Tony Robinson (speech recognition)|title=Several Improvements to a Recurrent Error Propagation Network Phone Recognition System |journal=Cambridge University Engineering Department Technical Report |date=30 September 1991 |volume=CUED/F-INFENG/TR82 |doi=10.13140/RG.2.2.15418.90567 }}</ref>|| 26.1', 145 => '|-', 146 => '| Bayesian Triphone GMM-HMM || 25.6', 147 => '|-', 148 => '| Hidden Trajectory (Generative) Model|| 24.8', 149 => '|-', 150 => '| Monophone Randomly Initialized DNN|| 23.4', 151 => '|-', 152 => '| Monophone DBN-DNN|| 22.4', 153 => '|-', 154 => '| Triphone GMM-HMM with BMMI Training|| 21.7', 155 => '|-', 156 => '| Monophone DBN-DNN on fbank || 20.7', 157 => '|-', 158 => '| Convolutional DNN<ref name="CNN-2014">{{cite journal|last1=Abdel-Hamid|first1=O.|title=Convolutional Neural Networks for Speech Recognition|journal=IEEE/ACM Transactions on Audio, Speech, and Language Processing|date=2014|volume=22|issue=10|pages=1533–1545|doi=10.1109/taslp.2014.2339736|display-authors=etal|url=https://zenodo.org/record/891433}}</ref>|| 20.0', 159 => '|-', 160 => '| Convolutional DNN w. Heterogeneous Pooling|| 18.7', 161 => '|-', 162 => '| Ensemble DNN/CNN/RNN<ref name="EnsembleDL">{{cite journal|last2=Platt|first2=J.|date=2014|title=Ensemble Deep Learning for Speech Recognition|url=https://pdfs.semanticscholar.org/8201/55ecb57325503183253b8796de5f4535eb16.pdf|journal=Proc. Interspeech|pages=|via=|last1=Deng|first1=L.}}</ref>|| 18.3', 163 => '|-', 164 => '| Bidirectional LSTM|| 17.9', 165 => '|-', 166 => '| Hierarchical Convolutional Deep Maxout Network<ref name="HCDMM">{{cite journal|last1=Tóth|first1=Laszló|date=2015|title=Phone Recognition with Hierarchical Convolutional Deep Maxout Networks|journal=EURASIP Journal on Audio, Speech, and Music Processing|volume=2015|doi=10.1186/s13636-015-0068-3|url=http://publicatio.bibl.u-szeged.hu/5976/1/EURASIP2015.pdf}}</ref> || 16.5', 167 => '|}', 168 => '', 169 => 'The debut of DNNs for speaker recognition in the late 1990s and speech recognition around 2009-2011 and of LSTM around 2003-2007, accelerated progress in eight major areas:<ref name="BOOK2014" /><ref name="interspeech2014Keynote" /><ref name="ReferenceA" />', 170 => '', 171 => '* Scale-up/out and accelerated DNN training and decoding', 172 => '* Sequence discriminative training', 173 => '* Feature processing by deep models with solid understanding of the underlying mechanisms', 174 => '* Adaptation of DNNs and related deep models', 175 => '* [[Multi-task learning|Multi-task]] and [[Inductive transfer|transfer learning]] by DNNs and related deep models', 176 => '* CNNs and how to design them to best exploit [[domain knowledge]] of speech', 177 => '* RNN and its rich LSTM variants', 178 => '* Other types of deep models including tensor-based models and integrated deep generative/discriminative models.', 179 => '', 180 => 'All major commercial speech recognition systems (e.g., Microsoft [[Cortana (software)|Cortana]], [[Xbox]], [[Skype Translator]], [[Amazon Alexa]], [[Google Now]], [[Siri|Apple Siri]], [[Baidu]] and [[IFlytek|iFlyTek]] voice search, and a range of [[Nuance Communications|Nuance]] speech products, etc.) are based on deep learning.<ref name=BOOK2014 /><ref>{{Cite journal|url=https://www.wired.com/2014/12/skype-used-ai-build-amazing-new-language-translator/|title=How Skype Used AI to Build Its Amazing New Language Translator {{!}} WIRED|journal=Wired|accessdate=2017-06-14|date=2014-12-17|last1=McMillan|first1=Robert}}</ref><ref name="Baidu">{{cite arxiv |eprint=1412.5567|last1=Hannun|first1=Awni|title=Deep Speech: Scaling up end-to-end speech recognition|last2=Case|first2=Carl|last3=Casper|first3=Jared|last4=Catanzaro|first4=Bryan|last5=Diamos|first5=Greg|last6=Elsen|first6=Erich|last7=Prenger|first7=Ryan|last8=Satheesh|first8=Sanjeev|last9=Sengupta|first9=Shubho|last10=Coates|first10=Adam|last11=Ng|first11=Andrew Y|class=cs.CL|year=2014}}</ref><ref>{{Cite web|url=http://research.microsoft.com/en-US/people/deng/ieee-icassp-plenary-2016-mar24-lideng-posted.pdf|title=Plenary presentation at ICASSP-2016|date=|website=|accessdate=}}</ref>', 181 => '', 182 => '=== Image recognition ===', 183 => '{{Main|Computer vision}}', 184 => '', 185 => 'A common evaluation set for image classification is the MNIST database data set. MNIST is composed of handwritten digits and includes 60,000 training examples and 10,000 test examples. As with TIMIT, its small size lets users test multiple configurations. A comprehensive list of results on this set is available.<ref name="YANNMNIST">{{cite web|url=http://yann.lecun.com/exdb/mnist/.|title=MNIST handwritten digit database, Yann LeCun, Corinna Cortes and Chris Burges|website=yann.lecun.com}}</ref>', 186 => '', 187 => 'Deep learning-based image recognition has become "superhuman", producing more accurate results than human contestants. This first occurred in 2011.<ref name=":7">{{Cite journal|last=Cireşan|first=Dan|last2=Meier|first2=Ueli|last3=Masci|first3=Jonathan|last4=Schmidhuber|first4=Jürgen|date=August 2012|title=Multi-column deep neural network for traffic sign classification|journal=Neural Networks|series=Selected Papers from IJCNN 2011|volume=32|pages=333–338|doi=10.1016/j.neunet.2012.02.023|pmid=22386783|citeseerx=10.1.1.226.8219}}</ref>', 188 => '', 189 => 'Deep learning-trained vehicles now interpret 360° camera views.<ref>[http://www.technologyreview.com/news/533936/nvidia-demos-a-car-computer-trained-with-deep-learning/ Nvidia Demos a Car Computer Trained with "Deep Learning"] (2015-01-06), David Talbot, ''[[MIT Technology Review]]''</ref> Another example is Facial Dysmorphology Novel Analysis (FDNA) used to analyze cases of human malformation connected to a large database of genetic syndromes.', 190 => '', 191 => '=== Visual art processing ===', 192 => 'Closely related to the progress that has been made in image recognition is the increasing application of deep learning techniques to various visual art tasks. DNNs have proven themselves capable, for example, of a) identifying the style period of a given painting, b) [[Neural Style Transfer]] - capturing the style of a given artwork and applying it in a visually pleasing manner to an arbitrary photograph or video, and c) generating striking imagery based on random visual input fields.<ref>{{cite journal |author1=G. W. Smith|author2=Frederic Fol Leymarie|date=10 April 2017|title=The Machine as Artist: An Introduction|journal=Arts|volume=6|issue=4|pages=5|doi=10.3390/arts6020005}}</ref><ref>{{cite journal |author=Blaise Agüera y Arcas|date=29 September 2017|title=Art in the Age of Machine Intelligence|journal=Arts|volume=6|issue=4|pages=18|doi=10.3390/arts6040018}}</ref>', 193 => '', 194 => '=== Natural language processing ===', 195 => '{{Main|Natural language processing}}', 196 => 'Neural networks have been used for implementing language models since the early 2000s.<ref name="gers2001" /><ref>{{Cite journal|last=Bengio|first=Yoshua|last2=Ducharme|first2=Réjean|last3=Vincent|first3=Pascal|last4=Janvin|first4=Christian|date=March 2003|title=A Neural Probabilistic Language Model|url=http://dl.acm.org/citation.cfm?id=944919.944966|journal=J. Mach. Learn. Res.|volume=3|pages=1137–1155|issn=1532-4435}}</ref> LSTM helped to improve machine translation and language modeling.<ref name="NIPS2014" /><ref name="vinyals2016" /><ref name="gillick2015" />', 197 => '', 198 => 'Other key techniques in this field are negative sampling<ref name="GoldbergLevy2014">{{cite arXiv|last1=Goldberg|first1=Yoav|last2=Levy|first2=Omar|title=word2vec Explained: Deriving Mikolov et al.'s Negative-Sampling Word-Embedding Method|eprint=1402.3722|class=cs.CL|year=2014}}</ref> and [[word embedding]]. Word embedding, such as ''[[word2vec]]'', can be thought of as a representational layer in a deep learning architecture that transforms an atomic word into a positional representation of the word relative to other words in the dataset; the position is represented as a point in a [[vector space]]. Using word embedding as an RNN input layer allows the network to parse sentences and phrases using an effective compositional vector grammar. A compositional vector grammar can be thought of as [[probabilistic context free grammar]] (PCFG) implemented by an RNN.<ref name="SocherManning2014">{{cite web|last1=Socher|first1=Richard|last2=Manning|first2=Christopher|title=Deep Learning for NLP|url=http://nlp.stanford.edu/courses/NAACL2013/NAACL2013-Socher-Manning-DeepLearning.pdf|accessdate=26 October 2014}}</ref> Recursive auto-encoders built atop word embeddings can assess sentence similarity and detect paraphrasing.<ref name="SocherManning2014" /> Deep neural architectures provide the best results for [[Statistical parsing|constituency parsing]],<ref>{{Cite journal |url= http://aclweb.org/anthology/P/P13/P13-1045.pdf|title = Parsing With Compositional Vector Grammars|last = Socher|first = Richard|date = 2013|journal = Proceedings of the ACL 2013 Conference|accessdate = |doi = |pmid = |last2 = Bauer|first2 = John|last3 = Manning|first3 = Christopher|last4 = Ng|first4 = Andrew}}</ref> [[sentiment analysis]],<ref>{{Cite journal |url= http://nlp.stanford.edu/~socherr/EMNLP2013_RNTN.pdf|title = Recursive Deep Models for Semantic Compositionality Over a Sentiment Treebank|last = Socher|first = Richard|date = 2013 |accessdate = |doi = |pmid =}}</ref> information retrieval,<ref>{{Cite journal|last=Shen|first=Yelong|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Mesnil|first5=Gregoire|date=2014-11-01|title=A Latent Semantic Model with Convolutional-Pooling Structure for Information Retrieval|url=https://www.microsoft.com/en-us/research/publication/a-latent-semantic-model-with-convolutional-pooling-structure-for-information-retrieval/|journal=Microsoft Research}}</ref><ref>{{Cite journal|last=Huang|first=Po-Sen|last2=He|first2=Xiaodong|last3=Gao|first3=Jianfeng|last4=Deng|first4=Li|last5=Acero|first5=Alex|last6=Heck|first6=Larry|date=2013-10-01|title=Learning Deep Structured Semantic Models for Web Search using Clickthrough Data|url=https://www.microsoft.com/en-us/research/publication/learning-deep-structured-semantic-models-for-web-search-using-clickthrough-data/|journal=Microsoft Research}}</ref> spoken language understanding,<ref name="IEEE-TASL2015">{{cite journal | last1 = Mesnil | first1 = G. | last2 = Dauphin | first2 = Y. | last3 = Yao | first3 = K. | last4 = Bengio | first4 = Y. | last5 = Deng | first5 = L. | last6 = Hakkani-Tur | first6 = D. | last7 = He | first7 = X. | last8 = Heck | first8 = L. | last9 = Tur | first9 = G. | last10 = Yu | first10 = D. | last11 = Zweig | first11 = G. | year = 2015 | title = Using recurrent neural networks for slot filling in spoken language understanding | url= https://www.semanticscholar.org/paper/41911ef90a225a82597a2b576346759ea9c34247| journal = IEEE Transactions on Audio, Speech, and Language Processing | volume = 23 | issue = 3| pages = 530–539 | doi=10.1109/taslp.2014.2383614}}</ref> machine translation,<ref name="NIPS2014">{{Cite journal|last=Sutskever|first=L.|last2=Vinyals|first2=O.|last3=Le|first3=Q.|date=2014|title=Sequence to Sequence Learning with Neural Networks|url=https://papers.nips.cc/paper/5346-sequence-to-sequence-learning-with-neural-networks.pdf|journal=Proc. NIPS|pages=|via=|bibcode=2014arXiv1409.3215S|arxiv=1409.3215}}</ref><ref name="auto">{{Cite journal|last=Gao|first=Jianfeng|last2=He|first2=Xiaodong|last3=Yih|first3=Scott Wen-tau|last4=Deng|first4=Li|date=2014-06-01|title=Learning Continuous Phrase Representations for Translation Modeling|url=https://www.microsoft.com/en-us/research/publication/learning-continuous-phrase-representations-for-translation-modeling/|journal=Microsoft Research}}</ref> contextual entity linking,<ref name="auto"/> writing style recognition,<ref name="BROC2017">{{Cite journal |doi = 10.1002/dac.3259|title = Authorship verification using deep belief network systems|journal = International Journal of Communication Systems|volume = 30|issue = 12|pages = e3259|year = 2017|last1 = Brocardo|first1 = Marcelo Luiz|last2 = Traore|first2 = Issa|last3 = Woungang|first3 = Isaac|last4 = Obaidat|first4 = Mohammad S.}}</ref> Text classification and others.<ref>{{Cite news|url=https://www.microsoft.com/en-us/research/project/deep-learning-for-natural-language-processing-theory-and-practice-cikm2014-tutorial/|title=Deep Learning for Natural Language Processing: Theory and Practice (CIKM2014 Tutorial) - Microsoft Research|work=Microsoft Research|accessdate=2017-06-14}}</ref>', 199 => '', 200 => 'Recent developments generalize [[word embedding]] to [[sentence embedding]].', 201 => '', 202 => '[[Google Translate]] (GT) uses a large [[End-to-end principle|end-to-end]] long short-term memory network.<ref name="GT_Turovsky_2016">{{cite web|url=https://blog.google/products/translate/found-translation-more-accurate-fluent-sentences-google-translate/|title=Found in translation: More accurate, fluent sentences in Google Translate|last=Turovsky|first=Barak|date=November 15, 2016|website=The Keyword Google Blog|accessdate=March 23, 2017}}</ref><ref name="googleblog_GNMT_2016">{{cite web|url=https://research.googleblog.com/2016/11/zero-shot-translation-with-googles.html|title=Zero-Shot Translation with Google's Multilingual Neural Machine Translation System|last1=Schuster|first1=Mike|last2=Johnson|first2=Melvin|date=November 22, 2016|website=Google Research Blog|accessdate=March 23, 2017|last3=Thorat|first3=Nikhil}}</ref><ref name="lstm1997">{{Cite journal|author=Sepp Hochreiter|author2=Jürgen Schmidhuber|year=1997|title=Long short-term memory|url=https://www.researchgate.net/publication/13853244|journal=[[Neural Computation (journal)|Neural Computation]]|volume=9|issue=8|pages=1735–1780|doi=10.1162/neco.1997.9.8.1735|pmid=9377276|via=}}</ref><ref name="lstm2000">{{Cite journal|author=Felix A. Gers|author2=Jürgen Schmidhuber|author3=Fred Cummins|year=2000|title=Learning to Forget: Continual Prediction with LSTM|journal=[[Neural Computation (journal)|Neural Computation]]|volume=12|issue=10|pages=2451–2471|doi=10.1162/089976600300015015|pmid=11032042|citeseerx=10.1.1.55.5709|url=https://www.semanticscholar.org/paper/11540131eae85b2e11d53df7f1360eeb6476e7f4}}</ref><ref name="GoogleTranslate">{{cite arXiv |eprint=1609.08144|last1=Wu|first1=Yonghui|title=Google's Neural Machine Translation System: Bridging the Gap between Human and Machine Translation|last2=Schuster|first2=Mike|last3=Chen|first3=Zhifeng|last4=Le|first4=Quoc V|last5=Norouzi|first5=Mohammad|last6=Macherey|first6=Wolfgang|last7=Krikun|first7=Maxim|last8=Cao|first8=Yuan|last9=Gao|first9=Qin|last10=Macherey|first10=Klaus|last11=Klingner|first11=Jeff|last12=Shah|first12=Apurva|last13=Johnson|first13=Melvin|last14=Liu|first14=Xiaobing|last15=Kaiser|first15=Łukasz|last16=Gouws|first16=Stephan|last17=Kato|first17=Yoshikiyo|last18=Kudo|first18=Taku|last19=Kazawa|first19=Hideto|last20=Stevens|first20=Keith|last21=Kurian|first21=George|last22=Patil|first22=Nishant|last23=Wang|first23=Wei|last24=Young|first24=Cliff|last25=Smith|first25=Jason|last26=Riesa|first26=Jason|last27=Rudnick|first27=Alex|last28=Vinyals|first28=Oriol|last29=Corrado|first29=Greg|last30=Hughes|first30=Macduff|display-authors=29|class=cs.CL|year=2016}}</ref><ref name="WiredGoogleTranslate">"An Infusion of AI Makes Google Translate More Powerful Than Ever." Cade Metz, WIRED, Date of Publication: 09.27.16. https://www.wired.com/2016/09/google-claims-ai-breakthrough-machine-translation/</ref> [[Google Neural Machine Translation|Google Neural Machine Translation (GNMT)]] uses an [[example-based machine translation]] method in which the system "learns from millions of examples."<ref name="googleblog_GNMT_2016" /> It translates "whole sentences at a time, rather than pieces. Google Translate supports over one hundred languages.<ref name="googleblog_GNMT_2016" /> The network encodes the "semantics of the sentence rather than simply memorizing phrase-to-phrase translations".<ref name="googleblog_GNMT_2016" /><ref name="Biotet">{{cite web|url=http://www-clips.imag.fr/geta/herve.blanchon/Pdfs/NLP-KE-10.pdf|title=MT on and for the Web|last1=Boitet|first1=Christian|last2=Blanchon|first2=Hervé|date=2010|accessdate=December 1, 2016|last3=Seligman|first3=Mark|last4=Bellynck|first4=Valérie}}</ref> GT uses English as an intermediate between most language pairs.<ref name="Biotet" />', 203 => '', 204 => '=== Drug discovery and toxicology ===', 205 => '{{For|more information|Drug discovery|Toxicology}}', 206 => 'A large percentage of candidate drugs fail to win regulatory approval. These failures are caused by insufficient efficacy (on-target effect), undesired interactions (off-target effects), or unanticipated [[Toxicity|toxic effects]].<ref name="ARROWSMITH2013">{{Cite journal', 207 => '| pmid = 23903212', 208 => '| year = 2013', 209 => '| last1 = Arrowsmith', 210 => '| first1 = J', 211 => '| title = Trial watch: Phase II and phase III attrition rates 2011-2012', 212 => '| journal = Nature Reviews Drug Discovery', 213 => '| volume = 12', 214 => '| issue = 8', 215 => '| pages = 569', 216 => '| last2 = Miller', 217 => '| first2 = P', 218 => '| doi = 10.1038/nrd4090', 219 => '| url = https://www.semanticscholar.org/paper/9ab0f468a64762ca5069335c776e1ab07fa2b3e2', 220 => '}}</ref><ref name="VERBIEST2015">{{Cite journal', 221 => '| pmid = 25582842', 222 => '| year = 2015', 223 => '| last1 = Verbist', 224 => '| first1 = B', 225 => '| title = Using transcriptomics to guide lead optimization in drug discovery projects: Lessons learned from the QSTAR project', 226 => '| journal = Drug Discovery Today', 227 => '| last2 = Klambauer', 228 => '| first2 = G', 229 => '| last3 = Vervoort', 230 => '| first3 = L', 231 => '| last4 = Talloen', 232 => '| first4 = W', 233 => '| last5 = The Qstar', 234 => '| first5 = Consortium', 235 => '| last6 = Shkedy', 236 => '| first6 = Z', 237 => '| last7 = Thas', 238 => '| first7 = O', 239 => '| last8 = Bender', 240 => '| first8 = A', 241 => '| last9 = Göhlmann', 242 => '| first9 = H. W.', 243 => '| last10 = Hochreiter', 244 => '| first10 = S', 245 => '| doi = 10.1016/j.drudis.2014.12.014', 246 => '| volume=20', 247 => '| issue = 5', 248 => '| pages=505–513', 249 => '}}</ref> Research has explored use of deep learning to predict the [[biomolecular target]]s,<ref name="MERCK2012" /><ref name=":5" /> [[off-target]]s, and [[Toxicity|toxic effects]] of environmental chemicals in nutrients, household products and drugs.<ref name="TOX21" /><ref name="TOX21Data" /><ref name=":11" />', 250 => '', 251 => 'AtomNet is a deep learning system for structure-based [[Drug design|rational drug design]].<ref>{{cite arXiv|title = AtomNet: A Deep Convolutional Neural Network for Bioactivity Prediction in Structure-based Drug Discovery|eprint= 1510.02855|date = 2015-10-09|first = Izhar|last = Wallach|first2 = Michael|last2 = Dzamba|first3 = Abraham|last3 = Heifets|class= cs.LG}}</ref> AtomNet was used to predict novel candidate biomolecules for disease targets such as the [[Ebola virus]]<ref>{{Cite news|title = Toronto startup has a faster way to discover effective medicines |url= https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/|website = The Globe and Mail |accessdate= 2015-11-09}}</ref> and [[multiple sclerosis]].<ref>{{Cite web|title = Startup Harnesses Supercomputers to Seek Cures |url= http://ww2.kqed.org/futureofyou/2015/05/27/startup-harnesses-supercomputers-to-seek-cures/|website = KQED Future of You|accessdate = 2015-11-09}}</ref><ref>{{cite web|url=https://www.theglobeandmail.com/report-on-business/small-business/starting-out/toronto-startup-has-a-faster-way-to-discover-effective-medicines/article25660419/%5D%20and%20multiple%20sclerosis%20%5B/|title=Toronto startup has a faster way to discover effective medicines}}</ref>', 252 => '', 253 => 'In 2019 generative neural networks were used to produce molecules that were validated experimentally all the way into mice.<ref>{{cite journal |last1=Zhavoronkov |first1=Alex|date=2019|title=Deep learning enables rapid identification of potent DDR1 kinase inhibitors |journal=Nature Biotechnology |volume=37|issue=9|pages=1038–1040|doi=10.1038/s41587-019-0224-x |pmid=31477924|url=https://www.semanticscholar.org/paper/d44ac0a7fd4734187bccafc4a2771027b8bb595e}}</ref><ref>{{cite journal |last1=Gregory |first1=Barber |title=A Molecule Designed By AI Exhibits 'Druglike' Qualities |url=https://www.wired.com/story/molecule-designed-ai-exhibits-druglike-qualities/ |journal=Wired}}</ref>', 254 => '', 255 => '=== Customer relationship management ===', 256 => '{{Main|Customer relationship management}}', 257 => 'Deep reinforcement learning has been used to approximate the value of possible [[direct marketing]] actions, defined in terms of [[RFM (customer value)|RFM]] variables. The estimated value function was shown to have a natural interpretation as [[customer lifetime value]].<ref>{{cite arxiv|last=Tkachenko |first=Yegor |title=Autonomous CRM Control via CLV Approximation with Deep Reinforcement Learning in Discrete and Continuous Action Space |date=April 8, 2015 |eprint=1504.01840|class=cs.LG }}</ref>', 258 => '', 259 => '=== Recommendation systems ===', 260 => '{{Main|Recommender system}}', 261 => 'Recommendation systems have used deep learning to extract meaningful features for a latent factor model for content-based music and journal recommendations.<ref>{{Cite book|url=http://papers.nips.cc/paper/5004-deep-content-based-music-recommendation.pdf|title=Advances in Neural Information Processing Systems 26|last=van den Oord|first=Aaron|last2=Dieleman|first2=Sander|last3=Schrauwen|first3=Benjamin|date=2013|publisher=Curran Associates, Inc.|editor-last=Burges|editor-first=C. J. C.|pages=2643–2651|editor-last2=Bottou|editor-first2=L.|editor-last3=Welling|editor-first3=M.|editor-last4=Ghahramani|editor-first4=Z.|editor-last5=Weinberger|editor-first5=K. Q.}}</ref><ref>X.Y. Feng, H. Zhang, Y.J. Ren, P.H. Shang, Y. Zhu, Y.C. Liang, R.C. Guan, D. Xu, (2019), "[https://www.jmir.org/2019/5/e12957/ The Deep Learning–Based Recommender System “Pubmender” for Choosing a Biomedical Publication Venue: Development and Validation Study]", ''[[Journal of Medical Internet Research]]'', 21 (5): e12957</ref> Multiview deep learning has been applied for learning user preferences from multiple domains.<ref>{{Cite journal|last=Elkahky|first=Ali Mamdouh|last2=Song|first2=Yang|last3=He|first3=Xiaodong|date=2015-05-01|title=A Multi-View Deep Learning Approach for Cross Domain User Modeling in Recommendation Systems|url=https://www.microsoft.com/en-us/research/publication/a-multi-view-deep-learning-approach-for-cross-domain-user-modeling-in-recommendation-systems/|journal=Microsoft Research}}</ref> The model uses a hybrid collaborative and content-based approach and enhances recommendations in multiple tasks.', 262 => '', 263 => '=== Bioinformatics ===', 264 => '{{Main|Bioinformatics}}', 265 => 'An [[autoencoder]] ANN was used in [[bioinformatics]], to predict [[Gene Ontology|gene ontology]] annotations and gene-function relationships.<ref>{{cite book|title=Deep Autoencoder Neural Networks for Gene Ontology Annotation Predictions |first1=Davide |last1=Chicco|first2=Peter|last2=Sadowski|first3=Pierre |last3=Baldi |date=1 January 2014|publisher=ACM|pages=533–540|doi=10.1145/2649387.2649442|journal=Proceedings of the 5th ACM Conference on Bioinformatics, Computational Biology, and Health Informatics - BCB '14|isbn=9781450328944 |hdl = 11311/964622|url=https://www.semanticscholar.org/paper/09f3132fdf103bdef1125ffbccb8b46f921b2ab7 }}</ref>', 266 => '', 267 => 'In medical informatics, deep learning was used to predict sleep quality based on data from wearables<ref>{{Cite journal|last=Sathyanarayana|first=Aarti|date=2016-01-01|title=Sleep Quality Prediction From Wearable Data Using Deep Learning|journal=JMIR mHealth and uHealth|volume=4|issue=4|doi=10.2196/mhealth.6562|pmid=27815231|pmc=5116102|pages=e125|url=https://www.semanticscholar.org/paper/c82884f9d6d39c8a89ac46b8f688669fb2931144}}</ref> and predictions of health complications from [[electronic health record]] data.<ref>{{Cite journal|last=Choi|first=Edward|last2=Schuetz|first2=Andy|last3=Stewart|first3=Walter F.|last4=Sun|first4=Jimeng|date=2016-08-13|title=Using recurrent neural network models for early detection of heart failure onset|url=http://jamia.oxfordjournals.org/content/early/2016/08/13/jamia.ocw112|journal=Journal of the American Medical Informatics Association|volume=24|issue=2|pages=361–370|doi=10.1093/jamia/ocw112|issn=1067-5027|pmid=27521897|pmc=5391725}}</ref> Deep learning has also showed efficacy in [[Artificial intelligence in healthcare|healthcare]].<ref>{{Cite web|url=https://medium.com/the-mission/deep-learning-in-healthcare-challenges-and-opportunities-d2eee7e2545|title=Deep Learning in Healthcare: Challenges and Opportunities|date=2016-08-12|website=Medium|access-date=2018-04-10}}</ref>', 268 => '', 269 => '=== Medical Image Analysis ===', 270 => 'Deep learning has been shown to produce competitive results in medical application such as cancer cell classification, lesion detection, organ segmentation and image enhancement<ref>{{Cite journal|last=Litjens|first=Geert|last2=Kooi|first2=Thijs|last3=Bejnordi|first3=Babak Ehteshami|last4=Setio|first4=Arnaud Arindra Adiyoso|last5=Ciompi|first5=Francesco|last6=Ghafoorian|first6=Mohsen|last7=van der Laak|first7=Jeroen A.W.M.|last8=van Ginneken|first8=Bram|last9=Sánchez|first9=Clara I.|date=December 2017|title=A survey on deep learning in medical image analysis|journal=Medical Image Analysis|volume=42|pages=60–88|doi=10.1016/j.media.2017.07.005|pmid=28778026|arxiv=1702.05747|bibcode=2017arXiv170205747L|url=https://www.semanticscholar.org/paper/2abde28f75a9135c8ed7c50ea16b7b9e49da0c09}}</ref><ref>{{Cite book |doi=10.1109/ICCVW.2017.18|isbn=9781538610343|chapter=Deep Convolutional Neural Networks for Detecting Cellular Changes Due to Malignancy|title=2017 IEEE International Conference on Computer Vision Workshops (ICCVW)|pages=82–89|year=2017|last1=Forslid|first1=Gustav|last2=Wieslander|first2=Hakan|last3=Bengtsson|first3=Ewert|last4=Wahlby|first4=Carolina|last5=Hirsch|first5=Jan-Michael|last6=Stark|first6=Christina Runow|last7=Sadanandan|first7=Sajith Kecheril|chapter-url=http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326160|url=https://www.semanticscholar.org/paper/6ae67bb4528bd5d922fd5a0c1a180ff1940f803c}}</ref>', 271 => '', 272 => '=== Mobile advertising ===', 273 => 'Finding the appropriate mobile audience for [[mobile advertising]] is always challenging, since many data points must be considered and analyzed before a target segment can be created and used in ad serving by any ad server.<ref>{{cite book |doi=10.1109/CSCITA.2017.8066548 |isbn=978-1-5090-4381-1|chapter=Predicting the popularity of instagram posts for a lifestyle magazine using deep learning|title=2017 2nd International Conference on Communication Systems, Computing and IT Applications (CSCITA)|pages=174–177|year=2017|last1=De|first1=Shaunak|last2=Maity|first2=Abhishek|last3=Goel|first3=Vritti|last4=Shitole|first4=Sanjay|last5=Bhattacharya|first5=Avik|chapter-url=https://www.semanticscholar.org/paper/c4389f8a63a7be58e007c183a49e491141f9e204}}</ref> Deep learning has been used to interpret large, many-dimensioned advertising datasets. Many data points are collected during the request/serve/click internet advertising cycle. This information can form the basis of machine learning to improve ad selection.', 274 => '', 275 => '=== Image restoration ===', 276 => 'Deep learning has been successfully applied to [[inverse problems]] such as [[denoising]], [[super-resolution]], [[inpainting]], and [[film colorization]].<ref>{{Cite web|url=https://blog.floydhub.com/colorizing-and-restoring-old-images-with-deep-learning/|title=Colorizing and Restoring Old Images with Deep Learning|date=2018-11-13|website=FloydHub Blog|language=en|access-date=2019-10-11}}</ref> These applications include learning methods such as "Shrinkage Fields for Effective Image Restoration"<ref>{{cite conference | url= http://research.uweschmidt.org/pubs/cvpr14schmidt.pdf |first1= Uwe |last1= Schmidt |first2= Stefan |last2= Roth |conference= Computer Vision and Pattern Recognition (CVPR), 2014 IEEE Conference on |title= Shrinkage Fields for Effective Image Restoration }}</ref> which trains on an image dataset, and [[Deep Image Prior]], which trains on the image that needs restoration.', 277 => '', 278 => '=== Financial fraud detection ===', 279 => 'Deep learning is being successfully applied to financial [[fraud detection]] and anti-money laundering. "Deep anti-money laundering detection system can spot and recognize relationships and similarities between data and, further down the road, learn to detect anomalies or classify and predict specific events". The solution leverages both supervised learning techniques, such as the classification of suspicious transactions, and unsupervised learning, e.g. anomaly detection.', 280 => '<ref>{{cite journal', 281 => '|first=Tomasz |last=Czech', 282 => '|title=Deep learning: the next frontier for money laundering detection', 283 => '|url=https://www.globalbankingandfinance.com/deep-learning-the-next-frontier-for-money-laundering-detection/', 284 => '|journal=Global Banking and Finance Review', 285 => '}}</ref>', 286 => '', 287 => '=== Military ===', 288 => '', 289 => 'The United States Department of Defense applied deep learning to train robots in new tasks through observation.<ref name=":12">{{Cite web|url=https://www.eurekalert.org/pub_releases/2018-02/uarl-ard020218.php|title=Army researchers develop new algorithms to train robots|website=EurekAlert!|access-date=2018-08-29}}</ref>', 290 => '', 291 => '== Relation to human cognitive and brain development ==', 292 => 'Deep learning is closely related to a class of theories of [[brain development]] (specifically, neocortical development) proposed by [[cognitive neuroscientist]]s in the early 1990s.<ref name="UTGOFF">{{cite journal | last1 = Utgoff | first1 = P. E. | last2 = Stracuzzi | first2 = D. J. | year = 2002 | title = Many-layered learning | url= https://www.semanticscholar.org/paper/398c477f674b228fec7f3f418a8cec047e2dafe5| journal = Neural Computation | volume = 14 | issue = 10| pages = 2497–2529 | doi=10.1162/08997660260293319| pmid = 12396572 }}</ref><ref name="ELMAN">{{cite book|url={{google books |plainurl=y |id=vELaRu_MrwoC}}|title=Rethinking Innateness: A Connectionist Perspective on Development|last=Elman|first=Jeffrey L.|publisher=MIT Press|year=1998|isbn=978-0-262-55030-7}}</ref><ref name="SHRAGER">{{cite journal | last1 = Shrager | first1 = J. | last2 = Johnson | first2 = MH | year = 1996 | title = Dynamic plasticity influences the emergence of function in a simple cortical array | url= | journal = Neural Networks | volume = 9 | issue = 7| pages = 1119–1129 | doi=10.1016/0893-6080(96)00033-0| pmid = 12662587 }}</ref><ref name="QUARTZ">{{cite journal | last1 = Quartz | first1 = SR | last2 = Sejnowski | first2 = TJ | year = 1997 | title = The neural basis of cognitive development: A constructivist manifesto | url= | journal = Behavioral and Brain Sciences | volume = 20 | issue = 4| pages = 537–556 | doi=10.1017/s0140525x97001581| pmid = 10097006 | citeseerx = 10.1.1.41.7854 }}</ref> These developmental theories were instantiated in computational models, making them predecessors of deep learning systems. These developmental models share the property that various proposed learning dynamics in the brain (e.g., a wave of [[nerve growth factor]]) support the [[self-organization]] somewhat analogous to the neural networks utilized in deep learning models. Like the [[neocortex]], neural networks employ a hierarchy of layered filters in which each layer considers information from a prior layer (or the operating environment), and then passes its output (and possibly the original input), to other layers. This process yields a self-organizing stack of [[transducer]]s, well-tuned to their operating environment. A 1995 description stated, "...the infant's brain seems to organize itself under the influence of waves of so-called trophic-factors ... different regions of the brain become connected sequentially, with one layer of tissue maturing before another and so on until the whole brain is mature."<ref name="BLAKESLEE">S. Blakeslee., "In brain's early growth, timetable may be critical," ''The New York Times, Science Section'', pp. B5–B6, 1995.</ref>', 293 => '', 294 => 'A variety of approaches have been used to investigate the plausibility of deep learning models from a neurobiological perspective. On the one hand, several variants of the [[backpropagation]] algorithm have been proposed in order to increase its processing realism.<ref>{{Cite journal|last=Mazzoni|first=P.|last2=Andersen|first2=R. A.|last3=Jordan|first3=M. I.|date=1991-05-15|title=A more biologically plausible learning rule for neural networks.|journal=Proceedings of the National Academy of Sciences|volume=88|issue=10|pages=4433–4437|doi=10.1073/pnas.88.10.4433|issn=0027-8424|pmid=1903542|pmc=51674|bibcode=1991PNAS...88.4433M}}</ref><ref>{{Cite journal|last=O'Reilly|first=Randall C.|date=1996-07-01|title=Biologically Plausible Error-Driven Learning Using Local Activation Differences: The Generalized Recirculation Algorithm|journal=Neural Computation|volume=8|issue=5|pages=895–938|doi=10.1162/neco.1996.8.5.895|issn=0899-7667|url=https://www.semanticscholar.org/paper/ed9133009dd451bd64215cca7deba6e0b8d7c7b1}}</ref> Other researchers have argued that unsupervised forms of deep learning, such as those based on hierarchical [[generative model]]s and [[deep belief network]]s, may be closer to biological reality.<ref>{{Cite journal|last=Testolin|first=Alberto|last2=Zorzi|first2=Marco|date=2016|title=Probabilistic Models and Generative Neural Networks: Towards an Unified Framework for Modeling Normal and Impaired Neurocognitive Functions|journal=Frontiers in Computational Neuroscience|volume=10|pages=73|doi=10.3389/fncom.2016.00073|pmid=27468262|pmc=4943066|issn=1662-5188|url=https://www.semanticscholar.org/paper/9ff36a621ee2c831fbbda5b719942f9ed8ac844f}}</ref><ref>{{Cite journal|last=Testolin|first=Alberto|last2=Stoianov|first2=Ivilin|last3=Zorzi|first3=Marco|date=September 2017|title=Letter perception emerges from unsupervised deep learning and recycling of natural image features|journal=Nature Human Behaviour|volume=1|issue=9|pages=657–664|doi=10.1038/s41562-017-0186-2|pmid=31024135|issn=2397-3374|url=https://www.semanticscholar.org/paper/ec2463bd610dcb30d67681160e895761e2dde482}}</ref> In this respect, generative neural network models have been related to neurobiological evidence about sampling-based processing in the cerebral cortex.<ref>{{Cite journal|last=Buesing|first=Lars|last2=Bill|first2=Johannes|last3=Nessler|first3=Bernhard|last4=Maass|first4=Wolfgang|date=2011-11-03|title=Neural Dynamics as Sampling: A Model for Stochastic Computation in Recurrent Networks of Spiking Neurons|journal=PLOS Computational Biology|volume=7|issue=11|pages=e1002211|doi=10.1371/journal.pcbi.1002211|pmid=22096452|pmc=3207943|issn=1553-7358|bibcode=2011PLSCB...7E2211B|url=https://www.semanticscholar.org/paper/e4e100e44bf7618c7d96188605fd9870012bdb50}}</ref>', 295 => '', 296 => 'Although a systematic comparison between the human brain organization and the neuronal encoding in deep networks has not yet been established, several analogies have been reported. For example, the computations performed by deep learning units could be similar to those of actual neurons<ref>{{Cite journal|last=Morel|first=Danielle|last2=Singh|first2=Chandan|last3=Levy|first3=William B.|date=2018-01-25|title=Linearization of excitatory synaptic integration at no extra cost|journal=Journal of Computational Neuroscience|volume=44|issue=2|pages=173–188|doi=10.1007/s10827-017-0673-5|pmid=29372434|issn=0929-5313|url=https://www.semanticscholar.org/paper/3a528f2cde957d4e6417651f8005ca2ee81ca367}}</ref><ref>{{Cite journal|last=Cash|first=S.|last2=Yuste|first2=R.|date=February 1999|title=Linear summation of excitatory inputs by CA1 pyramidal neurons|journal=Neuron|volume=22|issue=2|pages=383–394|issn=0896-6273|pmid=10069343|doi=10.1016/s0896-6273(00)81098-3}}</ref> and neural populations.<ref>{{Cite journal|date=2004-08-01|title=Sparse coding of sensory inputs|journal=Current Opinion in Neurobiology|volume=14|issue=4|pages=481–487|doi=10.1016/j.conb.2004.07.007|pmid=15321069|issn=0959-4388 | last1 = Olshausen | first1 = B | last2 = Field | first2 = D|url=https://www.semanticscholar.org/paper/0dd289358b14f8176adb7b62bf2fb53ea62b3818}}</ref> Similarly, the representations developed by deep learning models are similar to those measured in the primate visual system<ref>{{Cite journal|last=Yamins|first=Daniel L K|last2=DiCarlo|first2=James J|date=March 2016|title=Using goal-driven deep learning models to understand sensory cortex|journal=Nature Neuroscience|volume=19|issue=3|pages=356–365|doi=10.1038/nn.4244|pmid=26906502|issn=1546-1726|url=https://www.semanticscholar.org/paper/94c4ba7246f781632aa68ca5b1acff0fdbb2d92f}}</ref> both at the single-unit<ref>{{Cite journal|last=Zorzi|first=Marco|last2=Testolin|first2=Alberto|date=2018-02-19|title=An emergentist perspective on the origin of number sense|journal=Phil. Trans. R. Soc. B|volume=373|issue=1740|pages=20170043|doi=10.1098/rstb.2017.0043|issn=0962-8436|pmid=29292348|pmc=5784047|url=https://www.semanticscholar.org/paper/c91db0c8349a78384f54c6a9a98370f5c9381b6c}}</ref> and at the population<ref>{{Cite journal|last=Güçlü|first=Umut|last2=van Gerven|first2=Marcel A. J.|date=2015-07-08|title=Deep Neural Networks Reveal a Gradient in the Complexity of Neural Representations across the Ventral Stream|journal=Journal of Neuroscience|volume=35|issue=27|pages=10005–10014|doi=10.1523/jneurosci.5023-14.2015|pmid=26157000|pmc=6605414|arxiv=1411.6422}}</ref> levels.', 297 => '', 298 => '== Commercial activity ==', 299 => '[[Facebook]]'s AI lab performs tasks such as [[Automatic image annotation|automatically tagging uploaded pictures]] with the names of the people in them.<ref name="METZ2013">{{cite magazine|first=C. |last=Metz |title=Facebook's 'Deep Learning' Guru Reveals the Future of AI |url=https://www.wired.com/wiredenterprise/2013/12/facebook-yann-lecun-qa/ |magazine=Wired |date=12 December 2013}}</ref>', 300 => '', 301 => 'Google's [[DeepMind Technologies]] developed a system capable of learning how to play [[Atari]] video games using only pixels as data input. In 2015 they demonstrated their [[AlphaGo]] system, which learned the game of [[Go (game)|Go]] well enough to beat a professional Go player.<ref>{{Cite web|title = Google AI algorithm masters ancient game of Go |url= http://www.nature.com/news/google-ai-algorithm-masters-ancient-game-of-go-1.19234|website = Nature News & Comment|accessdate = 2016-01-30}}</ref><ref>{{Cite journal|title = Mastering the game of Go with deep neural networks and tree search|journal = [[Nature (journal)|Nature]]| issn= 0028-0836|pages = 484–489|volume = 529|issue = 7587|doi = 10.1038/nature16961|pmid = 26819042|first1 = David|last1 = Silver|author-link1=David Silver (programmer)|first2 = Aja|last2 = Huang|author-link2=Aja Huang|first3 = Chris J.|last3 = Maddison|first4 = Arthur|last4 = Guez|first5 = Laurent|last5 = Sifre|first6 = George van den|last6 = Driessche|first7 = Julian|last7 = Schrittwieser|first8 = Ioannis|last8 = Antonoglou|first9 = Veda|last9 = Panneershelvam|first10= Marc|last10= Lanctot|first11= Sander|last11= Dieleman|first12=Dominik|last12= Grewe|first13= John|last13= Nham|first14= Nal|last14= Kalchbrenner|first15= Ilya|last15= Sutskever|author-link15=Ilya Sutskever|first16= Timothy|last16= Lillicrap|first17= Madeleine|last17= Leach|first18= Koray|last18= Kavukcuoglu|first19= Thore|last19= Graepel|first20= Demis |last20=Hassabis|author-link20=Demis Hassabis|date= 28 January 2016|bibcode = 2016Natur.529..484S|url = https://www.semanticscholar.org/paper/846aedd869a00c09b40f1f1f35673cb22bc87490}}{{closed access}}</ref><ref>{{Cite web|title = A Google DeepMind Algorithm Uses Deep Learning and More to Master the Game of Go {{!}} MIT Technology Review |url= http://www.technologyreview.com/news/546066/googles-ai-masters-the-game-of-go-a-decade-earlier-than-expected/|website = MIT Technology Review|accessdate = 2016-01-30}}</ref> [[Google Translate]] uses a neural network to translate between more than 100 languages.', 302 => '', 303 => 'In 2015, [[Blippar]] demonstrated a mobile [[augmented reality]] application that uses deep learning to recognize objects in real time.<ref>{{Cite web|title=Blippar Demonstrates New Real-Time Augmented Reality App|url=https://techcrunch.com/2015/12/08/blippar-demonstrates-new-real-time-augmented-reality-app/|website=TechCrunch}}</ref>', 304 => '', 305 => 'In 2017, Covariant.ai was launched, which focuses on integrating deep learning into factories.<ref>[https://www.nytimes.com/2017/11/06/technology/artificial-intelligence-start-up.html A.I. Researchers Leave Elon Musk Lab to Begin Robotics Start-Up]</ref>', 306 => '', 307 => 'As of 2008,<ref>{{Cite document|title=TAMER: Training an Agent Manually via Evaluative Reinforcement - IEEE Conference Publication|doi=10.1109/DEVLRN.2008.4640845}}</ref> researchers at [[University of Texas at Austin|The University of Texas at Austin]] (UT) developed a machine learning framework called Training an Agent Manually via Evaluative Reinforcement, or TAMER, which proposed new methods for robots or computer programs to learn how to perform tasks by interacting with a human instructor.<ref name=":12" /> First developed as TAMER, a new algorithm called Deep TAMER was later introduced in 2018 during a collaboration between [[U.S. Army Research Laboratory]] (ARL) and UT researchers. Deep TAMER used deep learning to provide a robot the ability to learn new tasks through observation.<ref name=":12" /> Using Deep TAMER, a robot learned a task with a human trainer, watching video streams or observing a human perform a task in-person. The robot later practiced the task with the help of some coaching from the trainer, who provided feedback such as “good job” and “bad job.”<ref>{{Cite web|url=https://governmentciomedia.com/talk-algorithms-ai-becomes-faster-learner|title=Talk to the Algorithms: AI Becomes a Faster Learner|website=governmentciomedia.com|access-date=2018-08-29}}</ref>', 308 => '', 309 => '== Criticism and comment ==', 310 => 'Deep learning has attracted both criticism and comment, in some cases from outside the field of computer science.', 311 => '', 312 => '=== Theory ===', 313 => '{{see also|Explainable AI}}', 314 => 'A main criticism concerns the lack of theory surrounding some methods.<ref>{{Cite web|url=https://medium.com/@GaryMarcus/in-defense-of-skepticism-about-deep-learning-6e8bfd5ae0f1|title=In defense of skepticism about deep learning|last=Marcus|first=Gary|date=2018-01-14|website=Gary Marcus|access-date=2018-10-11}}</ref> Learning in the most common deep architectures is implemented using well-understood gradient descent. However, the theory surrounding other algorithms, such as contrastive divergence is less clear.{{citation needed|date=July 2016}} (e.g., Does it converge? If so, how fast? What is it approximating?) Deep learning methods are often looked at as a [[black box]], with most confirmations done empirically, rather than theoretically.<ref name="Knight 2017">{{cite web | last=Knight | first=Will | title=DARPA is funding projects that will try to open up AI's black boxes | website=MIT Technology Review | date=2017-03-14 | url=https://www.technologyreview.com/s/603795/the-us-military-wants-its-autonomous-machines-to-explain-themselves/ | accessdate=2017-11-02}}</ref>', 315 => '', 316 => 'Others point out that deep learning should be looked at as a step towards realizing strong AI, not as an all-encompassing solution. Despite the power of deep learning methods, they still lack much of the functionality needed for realizing this goal entirely. Research psychologist Gary Marcus noted:<blockquote>"Realistically, deep learning is only part of the larger challenge of building intelligent machines. Such techniques lack ways of representing [[causality|causal relationships]] (...) have no obvious ways of performing [[inference|logical inferences]], and they are also still a long way from integrating abstract knowledge, such as information about what objects are, what they are for, and how they are typically used. The most powerful A.I. systems, like [[Watson (computer)|Watson]] (...) use techniques like deep learning as just one element in a very complicated ensemble of techniques, ranging from the statistical technique of [[Bayesian inference]] to [[deductive reasoning]]."<ref>{{cite magazine|url=https://www.newyorker.com/|title=Is "Deep Learning" a Revolution in Artificial Intelligence?|last=Marcus|first=Gary|date=November 25, 2012|magazine=The New Yorker|accessdate=2017-06-14}}</ref></blockquote>As an alternative to this emphasis on the limits of deep learning, one author speculated that it might be possible to train a machine vision stack to perform the sophisticated task of discriminating between "old master" and amateur figure drawings, and hypothesized that such a sensitivity might represent the rudiments of a non-trivial machine empathy.<ref>{{cite web|url=http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|title=Art and Artificial Intelligence|date=March 27, 2015|publisher=ArtEnt|author=Smith, G. W.|accessdate=March 27, 2015|url-status=bot: unknown|archiveurl=https://web.archive.org/web/20170625075845/http://artent.net/2015/03/27/art-and-artificial-intelligence-by-g-w-smith/|archivedate=June 25, 2017}}</ref> This same author proposed that this would be in line with anthropology, which identifies a concern with aesthetics as a key element of [[behavioral modernity]].<ref>{{cite web |url=http://repositriodeficheiros.yolasite.com/resources/Texto%2028.pdf |author=Mellars, Paul |date=February 1, 2005 |title=The Impossible Coincidence: A Single-Species Model for the Origins of Modern Human Behavior in Europe|publisher=Evolutionary Anthropology: Issues, News, and Reviews |accessdate=April 5, 2017}}</ref>', 317 => '', 318 => 'In further reference to the idea that artistic sensitivity might inhere within relatively low levels of the cognitive hierarchy, a published series of graphic representations of the internal states of deep (20-30 layers) neural networks attempting to discern within essentially random data the images on which they were trained<ref>{{cite web|url=http://googleresearch.blogspot.co.uk/2015/06/inceptionism-going-deeper-into-neural.html |author1=Alexander Mordvintsev |author2=Christopher Olah |author3=Mike Tyka |date=June 17, 2015 |title=Inceptionism: Going Deeper into Neural Networks |publisher=Google Research Blog |accessdate=June 20, 2015}}</ref> demonstrate a visual appeal: the original research notice received well over 1,000 comments, and was the subject of what was for a time the most frequently accessed article on ''[[The Guardian]]'s''<ref>{{cite news|url=https://www.theguardian.com/technology/2015/jun/18/google-image-recognition-neural-network-androids-dream-electric-sheep|title=Yes, androids do dream of electric sheep|date=June 18, 2015|newspaper=The Guardian|author=Alex Hern|accessdate=June 20, 2015}}</ref> website.', 319 => '', 320 => '=== Errors ===', 321 => 'Some deep learning architectures display problematic behaviors,<ref name=goertzel>{{cite web|first=Ben |last=Goertzel |title=Are there Deep Reasons Underlying the Pathologies of Today's Deep Learning Algorithms? |year=2015 |url=http://goertzel.org/DeepLearning_v1.pdf}}</ref> such as confidently classifying unrecognizable images as belonging to a familiar category of ordinary images<ref>{{cite arxiv |eprint=1412.1897|last1=Nguyen|first1=Anh|title=Deep Neural Networks are Easily Fooled: High Confidence Predictions for Unrecognizable Images|last2=Yosinski|first2=Jason|last3=Clune|first3=Jeff|class=cs.CV|year=2014}}</ref> and misclassifying minuscule perturbations of correctly classified images.<ref>{{cite arxiv |eprint=1312.6199|last1=Szegedy|first1=Christian|title=Intriguing properties of neural networks|last2=Zaremba|first2=Wojciech|last3=Sutskever|first3=Ilya|last4=Bruna|first4=Joan|last5=Erhan|first5=Dumitru|last6=Goodfellow|first6=Ian|last7=Fergus|first7=Rob|class=cs.CV|year=2013}}</ref> [[Ben Goertzel|Goertzel]] hypothesized that these behaviors are due to limitations in their internal representations and that these limitations would inhibit integration into heterogeneous multi-component [[artificial general intelligence]] (AGI) architectures.<ref name="goertzel" /> These issues may possibly be addressed by deep learning architectures that internally form states homologous to image-grammar<ref>{{cite journal | last1 = Zhu | first1 = S.C. | last2 = Mumford | first2 = D. | year = 2006| title = A stochastic grammar of images | url= | journal = Found. Trends Comput. Graph. Vis. | volume = 2 | issue = 4| pages = 259–362 | doi = 10.1561/0600000018| citeseerx = 10.1.1.681.2190 }}</ref> decompositions of observed entities and events.<ref name="goertzel"/> [[Grammar induction|Learning a grammar]] (visual or linguistic) from training data would be equivalent to restricting the system to [[commonsense reasoning]] that operates on concepts in terms of grammatical [[Production (computer science)|production rules]] and is a basic goal of both human language acquisition<ref>Miller, G. A., and N. Chomsky. "Pattern conception." Paper for Conference on pattern detection, University of Michigan. 1957.</ref> and [[artificial intelligence]] (AI).<ref>{{cite web|first=Jason |last=Eisner |title=Deep Learning of Recursive Structure: Grammar Induction |url=http://techtalks.tv/talks/deep-learning-of-recursive-structure-grammar-induction/58089/}}</ref>', 322 => '', 323 => '=== Cyber threat ===', 324 => 'As deep learning moves from the lab into the world, research and experience shows that artificial neural networks are vulnerable to hacks and deception.<ref>{{Cite web|url=https://gizmodo.com/hackers-have-already-started-to-weaponize-artificial-in-1797688425|title=Hackers Have Already Started to Weaponize Artificial Intelligence|website=Gizmodo|access-date=2019-10-11}}</ref> By identifying patterns that these systems use to function, attackers can modify inputs to ANNs in such a way that the ANN finds a match that human observers would not recognize. For example, an attacker can make subtle changes to an image such that the ANN finds a match even though the image looks to a human nothing like the search target. Such a manipulation is termed an “adversarial attack.”<ref>{{Cite web|url=https://www.dailydot.com/debug/adversarial-attacks-ai-mistakes/|title=How hackers can force AI to make dumb mistakes|date=2018-06-18|website=The Daily Dot|language=en|access-date=2019-10-11}}</ref> In 2016 researchers used one ANN to doctor images in trial and error fashion, identify another's focal points and thereby generate images that deceived it. The modified images looked no different to human eyes. Another group showed that printouts of doctored images then photographed successfully tricked an image classification system.<ref name=":4">{{Cite news|url=https://singularityhub.com/2017/10/10/ai-is-easy-to-fool-why-that-needs-to-change|title=AI Is Easy to Fool—Why That Needs to Change|last=|first=|date=2017-10-10|work=Singularity Hub|accessdate=2017-10-11}}</ref> One defense is reverse image search, in which a possible fake image is submitted to a site such as [[TinEye]] that can then find other instances of it. A refinement is to search using only parts of the image, to identify images from which that piece may have been taken'''.'''<ref>{{Cite journal|last=Gibney|first=Elizabeth|title=The scientist who spots fake videos|url=https://www.nature.com/news/the-scientist-who-spots-fake-videos-1.22784|journal=Nature|pages=|doi=10.1038/nature.2017.22784|via=|year=2017}}</ref>', 325 => '', 326 => 'Another group showed that certain [[Psychedelic art|psychedelic]] spectacles could fool a [[facial recognition system]] into thinking ordinary people were celebrities, potentially allowing one person to impersonate another. In 2017 researchers added stickers to [[stop sign]]s and caused an ANN to misclassify them.<ref name=":4" />', 327 => '', 328 => 'ANNs can however be further trained to detect attempts at deception, potentially leading attackers and defenders into an arms race similar to the kind that already defines the [[malware]] defense industry. ANNs have been trained to defeat ANN-based anti-malware software by repeatedly attacking a defense with malware that was continually altered by a [[genetic algorithm]] until it tricked the anti-malware while retaining its ability to damage the target.<ref name=":4" />', 329 => '', 330 => 'Another group demonstrated that certain sounds could make the [[Google Now]] voice command system open a particular web address that would download malware.<ref name=":4" />', 331 => '', 332 => 'In “data poisoning,” false data is continually smuggled into a machine learning system's training set to prevent it from achieving mastery.<ref name=":4" />', 333 => '', 334 => '=== Reliance on human [[microwork]] ===', 335 => 'Most Deep Learning systems rely on training and verification data that is generated and/or annotated by humans. It has been argued in [[Media studies|media philosophy]] that not only low-paid [[Clickworkers|clickwork]] (e.g. on [[Amazon Mechanical Turk]]) is regularly deployed for this purpose, but also implicit forms of human [[microwork]] that are often not recognized as such.<ref name=":13">{{Cite journal|last=Mühlhoff|first=Rainer|date=2019-11-06|title=Human-aided artificial intelligence: Or, how to run large computations in human brains? Toward a media sociology of machine learning|journal=New Media & Society|language=en|volume=|pages=146144481988533|doi=10.1177/1461444819885334|issn=1461-4448}}</ref> The philosopher Rainer Mühlhoff distinguishes five types of "machinic capture" of human microwork to generate training data: (1) [[gamification]] (the embedding of annotation or computation tasks in the flow of a game), (2) "trapping and tracking" (e.g. [[CAPTCHA]]s for image recognition or click-tracking on Google [[Search engine results page|search results pages]]), (3) exploitation of social motivations (e.g. [[Tag (Facebook)|tagging faces]] on [[Facebook]] to obtain labeled facial images), (4) [[information mining]] (e.g. by leveraging [[Quantified self|quantified-self]] devices such as [[activity tracker]]s) and (5) [[Clickworkers|clickwork]].<ref name=":13" /> Mühlhoff argues that in most commercial end-user applications of Deep Learning such as [[DeepFace|Facebook's face recognition system,]] the need for training data does not stop once an ANN is trained. Rather, there is a continued demand for human-generated verification data to constantly calibrate and update the ANN. For this purpose Facebook introduced the feature that once a user is automatically recognized in an image, they receive a notification. They can choose whether of not they like to be publicly labeled on the image, or tell Facebook that it is not them in the picture.<ref>{{Cite news|url=https://www.wired.com/story/facebook-will-find-your-face-even-when-its-not-tagged/|title=Facebook Can Now Find Your Face, Even When It's Not Tagged|work=Wired|access-date=2019-11-22|language=en|issn=1059-1028}}</ref> This user interface is a mechanism to generate "a constant stream of  verification data"<ref name=":13" /> to further train the network in real-time. As Mühlhoff argues, involvement of human users to generate training and verification data is so typical for most commercial end-user applications of Deep Learning that such systems may be referred to as "human-aided artificial intelligence".<ref name=":13" />', 336 => '', 337 => '== Shallowing deep neural networks ==', 338 => '', 339 => '{{technical|section|date=February 2020}}', 340 => 'Shallowing refers to reducing a pre-trained DNN to a smaller network with the same or similar performance.<ref>{{cite journal |last1= Chen|first1= S.|last2= Zhao|first2=Q.|date= 2018|title=Shallowing deep networks: Layer-wise pruning based on feature representations |url= |journal=Representations. IEEE Transactions on Pattern Analysis and Machine Intelligence |volume= 41|issue=12 |pages= 3048–56|doi=10.1109/TPAMI.2018.2874634 |pmid= 30296213|access-date=}}</ref> Training of DNN with further shallowing can produce more efficient systems than just training of smaller networks from scratch. Shallowing is the rebirth of pruning that developed in the 1980-1990s.<ref name= "Hassibi1993">{{cite conference ', 341 => '| url = ', 342 => '| title = Optimal brain surgeon and general network pruning', 343 => '| last1 = Hassibi', 344 => '| first1 = B.', 345 => '| last2 = Stork', 346 => '| first2 = D. G.', 347 => '| last3 = Wolff', 348 => '| first3 = G. J.', 349 => '| date = 1993', 350 => '| publisher = IEEE', 351 => '| book-title = IEEE International Conference on Neural Networks', 352 => '| pages = 293–299', 353 => '| volume = 1', 354 => '| location = San Francisco, CA, USA', 355 => '| doi = 10.1109/ICNN.1993.298572', 356 => '}}</ref><ref name= "Gordienko1993">', 357 => '{{cite conference ', 358 => '| url = ', 359 => '| title = Construction of efficient neural networks: algorithms and tests', 360 => '| last1 = Gordienko', 361 => '| first1 = P.', 362 => '| date = 1993', 363 => '| publisher = IEEE', 364 => '| book-title = Proceedings of 1993 International Conference on Neural Networks (IJCNN-93)', 365 => '| pages = 313–6', 366 => '| volume = 1', 367 => '| location = Nagoya, Japan', 368 => '| doi = 10.1109/IJCNN.1993.713920', 369 => '}}</ref> The main approach to pruning is to gradually remove network elements (synapses, neurons, blocks of neurons, or layers) that have little impact on performance evaluation. Various indicators of sensitivity are used that estimate the changes of performance after pruning. The simplest indicators use just values of transmitted signals and the synaptic weights (the zeroth order). More complex indicators use mean absolute values of partial derivatives of the cost function,<ref name= "Gordienko1993"/><ref name="GorbMirTsar1999">{{cite conference ', 370 => '| url = ', 371 => '| title = Generation of explicit knowledge from empirical data through pruning of trainable neural networks', 372 => '| last1 = Gorban', 373 => '| first1 = A. N.', 374 => '| last2 = Mirkes', 375 => '| first2 = E. M. ', 376 => '| last3 = Tsaregorodtsev', 377 => '| first3 = V. G.', 378 => '| date = 1999', 379 => '| publisher = IEEE', 380 => '| book-title = IJCNN'99. International Joint Conference on Neural Networks. Proceedings (Cat. No.99CH36339) ', 381 => '| pages = 4393–4398', 382 => '| location = Washington, DC, USA', 383 => '| doi = 10.1109/IJCNN.1999.830876', 384 => '| arxiv = cond-mat/0307083', 385 => '}}</ref> ', 386 => 'or even the second derivatives.<ref name= "Hassibi1993"/> The shallowing allows to reduce the necessary resources and makes the skills of neural network more explicit.<ref name="GorbMirTsar1999"/> It is used for image classification,<ref>{{cite journal |last1=Zhong |first1= G.|last2= Yan|first2= S.|last3= Huang|first3= K.|last4=Cai|first4=Y.|last5=Dong |first5= J.|date=2018|title= Reducing and stretching deep convolutional activation features for accurate image classification|url= |journal= Cogn. Comput.|volume= 10|issue= 1|pages=179–86|doi=10.1007/s12559-017-9515-z |access-date=}}</ref> for development of security systems,<ref name="MirkesDog2019">{{cite journal |last1=Gorban |first1= A. N.|last2=Mirkes |first2=E. M. |last3=Tyukin |first3= I. Y.|date= 2019|title=How deep should be the depth of convolutional neural networks: A backyard dog case study |url= |journal=Cogn. Comput.|volume= |issue= |pages= |doi= 10.1007/s12559-019-09667-7 | doi-access= free| arxiv= 1805.01516 }}</ref> for accelerating DNN execution on mobile devices,<ref>{{cite conference ', 387 => '| url = https://www.aaai.org/ocs/index.php/AAAI/AAAI18/paper/viewFile/16652/15946', 388 => '| title = DeepRebirth: Accelerating deep neural network execution on mobile devices', 389 => '| last1 = Li', 390 => '| first1 = D.', 391 => '| last2 = Wang', 392 => '| first2 = X.', 393 => '| last3 = Kong', 394 => '| first3 = D.', 395 => '| date = 2018', 396 => '| publisher = Association for the Advancement of Artificial Intelligence', 397 => '| book-title = Thirty-second AAAI conference on artificial intelligence (AAAI-18)', 398 => '| pages = ', 399 => '| location = ', 400 => '| doi = ', 401 => '| arxiv = 1708.04728', 402 => '}}', 403 => '</ref> and for other applications. It has been demonstrated that using linear postprocessing, such as supervised PCA, improves DNN performance after shallowing.<ref name="MirkesDog2019"/>', 404 => '', 405 => '== See also ==', 406 => '* [[Applications of artificial intelligence]]', 407 => '* [[Comparison of deep learning software]]', 408 => '* [[Compressed sensing]]', 409 => '* [[Echo state network]]', 410 => '* [[List of artificial intelligence projects]]', 411 => '* [[Liquid state machine]]', 412 => '* [[List of datasets for machine learning research]]', 413 => '* [[Reservoir computing]]', 414 => '* [[Sparse coding]]', 415 => '', 416 => '== References ==', 417 => '{{Reflist|30em}}', 418 => '', 419 => '== Further reading ==', 420 => '{{refbegin}}', 421 => '* {{cite book |title=Deep Learning |year=2016', 422 => '|first1=Ian |last1=Goodfellow |authorlink1=Ian Goodfellow', 423 => '|first2=Yoshua |last2=Bengio |authorlink2=Yoshua Bengio', 424 => '|first3=Aaron |last3=Courville', 425 => '|publisher=MIT Press', 426 => '|url=http://www.deeplearningbook.org', 427 => '|isbn=978-0-26203561-3', 428 => '|postscript=, introductory textbook.', 429 => '}}', 430 => '', 431 => '{{Prone to spam|date=June 2015}}{{Z148}}<!-- {{No more links}}', 432 => '', 433 => 'Please be cautious adding more external links.', 434 => '', 435 => 'Wikipedia is not a collection of links and should not be used for advertising.', 436 => '', 437 => 'Excessive or inappropriate links will be removed.', 438 => '', 439 => ' See [[Wikipedia:External links]] and [[Wikipedia:Spam]] for details.', 440 => '', 441 => 'If there are already suitable links, propose additions or replacements on', 442 => 'the article's talk page, or submit your link to the relevant category at', 443 => 'DMOZ (dmoz.org) and link there using {{Dmoz}}.', 444 => '', 445 => '-->', 446 => '', 447 => '[[Category:Deep learning| ]]', 448 => '[[Category:Artificial neural networks]]', 449 => '[[Category:Artificial intelligence]]', 450 => '[[Category:Emerging technologies]]' ]
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