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. (shrink)

Males are selectively afflicted with the neurodevelopmental and psychiatric disorders of childhood, a broad and virtually ubiquitous phenomenon that has not received proper attention in the biological study of sex differences. The previous literature has alluded to psychosocial differences, genetic factors and elements pertaining to male “complexity” and relative immaturity, but these are not deemed an adequate explanation for selective male affliction. The structure of sex differences in neurodevelopmental disorders is hypothesized to contain these elements: Males are more frequently afflicted, (...) females more severely; disorders arising in females are largely mediated by the genotype; in males, by a genotype by environment interaction; complications of pregnancy and delivery occur more frequently with male births; such complications are decisive and influence subsequent development. We hypothesize that there is something about the male fetus that evokes an inhospitable uterine environment. This “evocative principle” is hypothesized to relate to the relative antigenicity of the male fetus, which may induce a state of maternal immunoreactivity, leading either directly or indirectly to fetal damage. The immunoreactive theory thus constructed is borrowed from studies of sex ratios and is the only explanation consistent with negative parity effects in the occurrence of pregnancy complications and certain neurodevelopmental disorders. Although the theory is necessarily speculative, it is heuristic and hypotheses derived from it are proposed; some are confirmed in the existing literature and by the authors' research. (shrink)

Life history theory’s principle of allocation suggests that because immature organisms cannot expend reproductive effort, the major trade-off facing juveniles will be the one between survival, on one hand, and growth and development, on the other. As a consequence, infants and children might be expected to possess psychobiological mechanisms for optimizing this trade-off. The main argument of this paper is that the attachment process serves this function and that individual differences in attachment organization (secure, insecure, and possibly others) may represent (...) facultative adaptations to conditions of risk and uncertainty that were probably recurrent in the environment of human evolutionary adaptedness. (shrink)