Abstract

New findings emerging from developmental behavior genetics indicate that individuals living in the same family develop in ways that make them remarkably different from each other despite the commonalities of shared genes and shared environments. These findings suggest that there are important factors residing within families that are not shared by family members that are nevertheless influential in development. The most discussed of these influences has been called "nonshared environment," meaning environmental influences that operate within families and that are uniquely experienced by particular family members. In this paper we explore the nature of nonshared influences on development, develop a set of criteria that any theoretical approach must incorporate to deal effectively with the development of individuality in light of these new findings, and offer an analysis of the extent to which these criteria can be incorporated by an established theory of environmental influence: radical behaviorism.