Do Peer Group Norms Moderate the Expression of Genetic Risk for Aggression?

• NCJ Number: 243869
• Journal: Journal of Criminal Justice Volume: 41 Issue: 5 Dated: September - October 2013 Pages: 324-330
• Author(s): Mara Brendgen; Alain Girard; Frank Vitaro; Ginette Dionne; Michel Boivin
• Date Published: October 2013
• Length: 7 pages
• Sponsoring Agency: Social Sciences and Humanities Research Council of Canada; Fonds québécois de la recherche sur la société et la culture (FQRSC)
• Publication Format: Article
• Publication Type: Research (Applied/Empirical); Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

Using a genetically informed research design based on twins raised together, this study examined whether the effect of genetic influences on physical aggression or "relational aggression" (nonphysical social interactions designed to inflict psychological and social harms on targeted victims) varies depending on peer group behavioral norms.

Abstract

As expected, a genetic predisposition for physical aggression was much more likely to be expressed when classroom norms were supportive of such behavior. In contrast, when physical aggression was met with strong disapproval and rejection by the peer group, genetic predispositions toward physical aggression was suppressed. This means that in such cases, environmental influences (peer group norms) trump genetic predispositions. Relational aggression, on the other hand, was consistently less explained by genetic influences and more by environmental influences, regardless of whether peer group norms were favorable or unfavorable toward that behavior. There was much less variability in relational aggression when this behavior was frowned upon than when it was rewarded by the peer group. Explanations are offered for these findings. The 192 twin pairs participating in this study were part of a population-based sample of 448 MZ and same-sex DZ twin pairs from the greater Montreal area. They were recruited at birth between November 1995 and July 1998. For a subsample of the same-sex twin pairs (n = 123), a DNA sample was evaluated with respect to 8-10 highly polymorphous genetic markers. Physical and relational aggression of each target child as well as of each of their respective classmates was measured, using peer nomination in each twin child's classroom. Peer group norm salience was operationalized as the extent to which each peer group made injunctive norms regarding physical or relational aggression salient through higher peer rejection of aggressive children. 2 tables, 1 figure, and 35 references