Visual expertise does not predict the composite effect across species: a comparison between spider (Ateles geoffroyi) and rhesus (Macaca mulatta) monkeys

Brain Cogn. 2009 Dec;71(3):187-95. doi: 10.1016/j.bandc.2009.09.002. Epub 2009 Oct 7.

Abstract

Humans are subject to the composite illusion: two identical top halves of a face are perceived as "different" when they are presented with different bottom halves. This observation suggests that when building a mental representation of a face, the underlying system perceives the whole face, and has difficulty decomposing facial features. We adapted a behavioural task that measures the composite illusion to examine the perception of faces in two nonhuman species. Specifically we had spider (Ateles geoffroyi) and rhesus monkeys (Macaca mulatta) perform a two-forced choice, match-to-sample task where only the top half of sample was relevant to the task. The results of Experiment 1 show that spider monkeys (N=2) process the faces of familiar species (conspecifics and humans, but not chimpanzees, sheep, or sticks), holistically. The second experiment tested rhesus monkeys (N=7) with the faces of humans, chimpanzees, gorillas, sheep, and sticks. Contrary to prediction, there was no evidence of a composite effect in the human (or familiar primate) condition. Instead, we present evidence of a composite illusion in the chimpanzee condition (an unfamiliar primate). Together, these experiments show that visual expertise does not predict the composite effect across the primate order.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Atelinae / physiology*
  • Attention / physiology
  • Chi-Square Distribution
  • Discrimination Learning / physiology
  • Face
  • Facial Expression
  • Female
  • Macaca mulatta / physiology*
  • Male
  • Optical Illusions / physiology*
  • Orientation / physiology
  • Pattern Recognition, Visual / physiology*
  • Photic Stimulation
  • Psychomotor Performance / physiology