In this commentary, I delineate several questions raised by the Hammond and Drummond (2019) paper: (a) to why there seems to be an association between state positive emotion and prosocial behavior in young children, and if and how early positively tinged prosocial behavior provides a pathway to (b) later prosocial behavior more generally…

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)

Notes that psychologists' interest in behavioral development concerns individual differences in behavior. Explores complexities of genetic and environmental determination of development, and of canalization. Intelligence is considered as an example of the canalization of human behavior. (BC)

Maintains that (1) research questions must address intra- and extraorganism contextual relations and must be multidisciplinary in scope; (2) research must be sensitive to contextual variability and individual differences; and (3) scholars must develop empirically generative models linking the development of human beings with changing contexts. (BC)