Introduction

Over the last half century, developmental research has undergone tremendous change. Our knowledge of how children develop in the physical, neurological, cognitive, and social domains has advanced greatly. In some areas, progress has been so extensive that old theories have been abandoned and textbooks completely rewritten (e.g., infant perceptual and cognitive development). Other advances are evident in the emergence of entire fields that did not even exist two or three decades ago (e.g., developmental neuroscience: Johnson, 1999; developmental connectionism: Elman, Bates, Johnson, Karmiloff-Smith, Parisi, & Plunkett, 1996). Still other, relatively “old” areas have moved in novel directions that have revealed new facts about how children develop (e.g., motor skills: Thelen, 1995; language: Markman, 1991; memory: Bruck & Ceci, 1999).

Theoretical approaches to developmental research have also changed dramatically in the past fifty years. For instance, in cognitive development research, radical behaviorism was replaced by Piagetian constructivism in the 1950s and 1960s, which itself was challenged by symbolic information processing theorists in the 1970s. The assumptions of symbolic information processing theories were later contested by connectionist theorists and domain-specificity theorists in the 1980s and 1990s. Nativist theories are also again in vogue after being marginalized for nearly a century. In addition, dynamic systems approaches derived from chaos theory in mathematics and thermodynamic research have been introduced to account for certain patterns of child development (Thelen & Smith, 1994; van Geert, 1991).