This issue's special section on canalization of behavioral development is introduced. In the special section, an invited paper by Gilbert Gottlieb, adopts a systems approach that stresses the complex interaction of genes, behavior, and environment. Several comments on the Gottlieb paper are also included. (BC)

Discusses the history of the hierarchical epigenetic systems view as applied to human development and offers examples of its implementation. Notes the agreement by many authors that the multilevel systems view is the right model for developmental psychology in both human and animal studies. (BC)

Applies a systems approach to the development of expressive and communicative action of infants in the first year of life. Hypothesizes that the systems approach (which integrates expressive and communicative actions with other elements of the infant's physiology, cognition, behavior, and social environment) will explain previously unexplained…

In contrast to earlier notions, a systems view of an organism's development sees genes as only one component in a hierarchy of influences that produces finished traits and differentiation. Developmental canalization proceeds from genes, behavior, and environment as well as from the coaction of these factors. (BC)