a1 Hebrew University of Jerusalem
a2 National University of Singapore
Theoretical considerations and new empirical evidence suggest that children's development cannot simply be explained by either genes or environment but that their interaction is important to understanding child behavior. In particular, a genetic polymorphism, the exon III repeat region of the dopamine receptor D4, has been the focus of interest regarding differential susceptibility to parental influence. To study environmental and genetic influences on children's prosocial behavior, 168 twin pairs (mean age = 44 months) participated in an experiment that assessed prosocial behavior via three measures: compliant prosocial behavior elicited in response to social requests, self-initiated prosocial behavior enacted voluntarily, and mothers' rating of children's behavior. Genetic effects accounted for 34% to 53% of the variance in prosocial behavior. The rest of the variance was accounted for by nonshared environment and error. Parenting measures of maternal positivity, negativity, and unexplained punishment did not correlate significantly with children's prosocial behavior. However, when parenting was stratified by presence or absence of the child's dopamine receptor D4 7-repeat allele in an overlapping sample of 167 children to model differential susceptibility to parental influence, a richer picture emerged. Positive parenting related meaningfully to mother-rated prosocial behavior, and unexplained punishment related positively to self-initiated prosocial behavior, but only among children carrying the 7-repeat allele. The findings demonstrate that a molecular genetic strategy, based on genotyping of common polymorphisms and combined with a classic twin approach, provides a richer description of how genes and environment interact to shape children's behavior, and allows for the identification of differential sensitivity to parental influence.
(Online publication January 24 2011)
The results from a partial sample were presented by the first author in an invited address at the Society for Research in Child Development meetings in Denver, CO, in 2009. The authors are indebted to the parents and twins in the Longitudinal Israeli Study of Twins for making the study possible. We thank Maayan Davidov, Barbara Oakley, and Michal Shauly for their insightful comments on parts of the paper. We also thank Ira Goldner, Tamar Gutbir, Maya Mekler, Gali Naor, Moran Shalmon, Dana Zahar, and the research assistants who collected and coded the data. The Longitudinal Israeli Study of Twins is supported by Grant 31/06 from the Israel Science Foundation (to A.K.). Genotyping was supported by a grant from the National Institute for Psychobiology in Israel (to A.K.).