Research in a variety of biological and social sciences in the past few decades has brought about substantial change in earlier understandings of the contributors to cognitive and behavioral function. In classic works by Galton (1869) and Burt et al. (1934), differences in intelligence were attributed to heredity, emphasizing a perception of the child as constitutionally separate from the environment. In the social sciences, however, a series of landmark studies in the 1930s and 1940s of infants and young children reared in institutions drew attention to the environmental and contextual contributors to child development (Ramey and Sackett, 2000). The research that ensued using animal models (Sackett et al., 1999), the study of children who experienced deprivation in institutional settings, and the proactive early intervention efforts in the 1960s collectively provided compelling evidence that early experience matters a great deal.
While genetic and physiological factors continue to play a central role in the understanding of cognitive and behavioral performance, the perception of the child as constitutionally separate from the environment no longer holds. Understanding the development of child behavior increasingly has required a focus on aspects of the environment that serve as moderators of performance (Sameroff, 1993; Ceci et al., 1997). The analytic lenses and