JPS 2001 was organized around implications of Piaget’s epigenetic concept of cognitive constructivism-his view that the developing child constructs sequentially more powerful schemes as he adapts (through assimilation and accommodation) to feedback he receives from his own actions on himself, on others, and on objects (Inhelder & Piaget, 1964; Piaget, 1952, 1954, 1962; Piaget & Inhelder, 1967), and as he reflects on this feedback (Piaget, 1985). The seminal idea is that the developing child constructs much of his own environment, which transforms him, and which he, in turn, transforms, and so on. (Likewise, of course, parents, siblings, and others construct much of the child’s environment and transform it in response to his changing nature.)

The term epigenetics, derived from the Aristotelian word epigenesis, was introduced in 1947 by Conrad Waddington (1975) to describe the “branch of biology, which studies the causal interactions between genes and their products which bring the phenotype into being” (p. 218). He describes the elementary processes of epigenetics as having two aspects: “changes in cellular composition (cellular differentiation, or histogenesis) and changes in geometrical form” (p. 219). Although Waddington focused on the embryological period of phenotype development, Piaget and others have extended the usage to later developmental stages because the interactions between genes and their products in transformations of the phenotype continue throughout the life cycle.