Dr. Stephen Suomi is Chief of the Laboratory of Comparative Ethology at the National Institute of Child Health and Human Development (NICHD), National Institutes of Health in Bethesda, Maryland. He also holds appointments as Research Professor at the University of Virginia, the University of Maryland, College Park, and The Johns Hopkins University, and is an Adjunct Professor at Pennsylvania State University and the University of Maryland, Baltimore County. Dr. Suomi studied Psychology at Stanford University, then continued as a graduate student at the University of Wisconsin-Madison, receiving his PhD. in Psychology. He then joined the Psychology faculty at the University of Wisconsin-Madison, where he eventually attained the rank of Professor. Since joining the NICHD he has identified heritable and experiential factors that influence individual biobehavioral development, characterized both behavioral and physiological features of distinctive rhesus monkey phenotypes, and demonstrated the adaptive significance of these different phenotypes in naturalistic settings. His present research focuses on three genera issues: the interaction between genetic and environmental factors in shaping individual developmental trajectories, the issue of continuity vs. change and the relative stability of individual differences throughout development, and the degree to which findings from monkeys studied in captivity generalize not only to monkeys living in the wild but also to humans living in different cultures.