During the past several decades, more and more investigators have focused their efforts on articulating the processes of ontogenesis in the perceptual, cognitive, socioemotional, linguistic, and representational domains of development in infants and children with Down syndrome. Recently, much of this work has been guided by the organizational perspective and has been conducted with the goal of expanding our knowledge of the normal developmental process (Cicchetti & Pogge-Hesse, 1982; Cicchetti & Sroufe, 1978). Studies of populations where varied patterns of development may occur as a consequence of the pervasive and enduring influences that mark the transaction between the child and the environment, such as with children with Down syndrome and their families, provide an appropriate basis for affirming, expanding, and challenging current development theory. Simultaneously, this approach allows for the formulation of a more comprehensive and integrative theory of normal development (Cicchetti, 1984, in press; Freud, 1965; Inhelder, 1966; Rutter, 1986; Werner, 1948). This “developmental” approach to Down syndrome is receiving increased attention in a variety of disciplines, including education, the neurosciences, pediatrics, psychiatry, and clinical and developmental psychology (see Hodapp & Zigler, Chapter 1, this volume).

Prior to these recent efforts, most investigators had conceptualized the developmental process of individuals with Down syndrome as necessarily being quantitatively and qualitatively different from that of mental-age-matched nonhandicapped children (for reviews, see Cicchetti & Pogge-Hesse, 1982; Hodapp & Zigler, Chapter 1, this volume).