In this article, we contrast evolutionary and psychobiological models of individual development to address the idea that individual development occurring in prototypically risky and unsupportive environments can be understood as adaptation. We question traditional evolutionary explanations of individual development, calling on the principle of…

We examined whether self-restraint in early childhood predicted individual differences in 3 executive functions (EFs; inhibiting prepotent responses, updating working memory, and shifting task sets) in late adolescence in a sample of approximately 950 twins. At ages 14, 20, 24, and 36 months, the children were shown an attractive toy and told not…

Authors investigated the hypothesis that differences in aggressive behavior may partly be a function of differences (a) in the perception of aggressive cues, or (b) in the degree in which retaliation is expected. (Authors)

Reflection-impulsivity was studied in preschoolers to clarify underlying behavioral dimensions, sex differences, and contribution of activity level, mental age, and socioeconomic status. Analyses replicate a previous finding that dimension of behavioral impulsivity characterizes children with long response latency and high error scores, not…

Findings are discussed in terms of traditional personality-trait theory and cognitive development theory. (Authors)

Measures of active sleep, quiet sleep, sucking, crying, body size and gestational age were factor analyzed for 137 normal newborns at 2 days of age. The results yielded 3 stable factors: reactivity-irritability, maturity, and reflexive and discriminative sucking. (JMB)

Younger men are both less engaged from the world and more efficient processors of information than older (especially less educated) ones. (Authors)

A study of the effect of the twin sibling relationship upon interactions between monkey mothers and infants. Findings provided strong support for the prediction that the twin sibling presence decreases the amount of behavior directed from infant to mother. Differences in maternal behavior were concluded to be reactions to differences in infant…