The etiology of social aggression

Social aggression (SA) is a form of antisocial behavior in which social relationships and social status are used to damage reputations and inflict emotional harm on others. Despite extensive research focused on understanding... [ view full abstract ]

Social aggression (SA) is a form of antisocial behavior in which social relationships and social status are used to damage reputations and inflict emotional harm on others. Despite extensive research focused on understanding the prevalence and consequences of SA, only three studies have examined the underlying etiology of these behaviors, with markedly inconsistent results.  Moreover, all of these studies relied on a classical twin design (CTD), which can result in biased heritability estimates when the strict assumptions of the design are violated.  The current study sought to overcome this limitation by estimating the etiology of SA using a nuclear twin family (NTF) design, which requires far fewer assumptions.  We also fit the CTD model using the same data to evaluate whether its assumptions may have biased previous heritability estimates.  Maternal-report, paternal-report, and teacher-report data were collected for twin SA (N=1,030 pairs). Self-report data was collected for parental SA.  The best-fitting NTF model for all informants was the ASFE model, indicating that additive genetic, sibling environmental, familial environmental, and non-shared environmental influences significantly contribute to the etiology of SA in middle childhood.  Unlike the NTF model, the best-fitting CTD model varied dramatically across informants.  Although the specific NTF parameter estimates varied, SA generally emerged as largely additive genetic (A=0.07-0.62) and sibling environmental (S=0.18-0.50) in origin.  The magnitude of S suggests that future research should attempt to identify specific sibling-level environmental influences that contribute to SA, such as peer groups, school experiences, parenting practices, and rearing neighborhood characteristics.  Lastly, research has shown that the NTFM is superior to the CTD because it provides more nuanced and precise heritability estimates. Our results indicate that it may also be robust to informant effects and, therefore, a more valid assessment of etiology for these phenotypes in which informant biases are problematic.