Over the past 8 years we have been involved in a study of the psychophysiological correlates of cognitive and affective behaviors during the first year of life. We have utilized recordings of brain electrical activity (the EEG) to describe differences in regional activation as well as, more recently, changes in regional connectivity. Our studies have indicated an important role for the frontal region in the expression of positive and negative emotions and in the regulation of emotional distress. In addition, individual differences in frontal EEG maturation seem to be associated with improved performance on tasks known to involve specific regions of frontal cortex. The corroborative data from different areas of study (studies of brain-damaged adults; studies of lesions in nonhuman primates) give us confidence that our measures of regional electrical activity are indeed reflecting true brain processes. Our continuing task is to understand the skills that are involved in these complex behaviors (such as AB performance or expression of affect) so as to better understand these important brain-behavior relationships.