Vol. 6, No. 4, 2000 Page 5 
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Vol. 6, No. 4, 2000 Page 5 |
Research continues to show a strong genetic effect on aggression, with a new study suggesting that this effect is especially strong for physically aggressive behavior.
Philip Vernon and colleagues studied 247 adult twin pairs. Of these, 183 were monozygotic (identical), while 64 were dizygotic (fraternal), same-sex pairs.
The researchers tested their subjects on 18 measures of aggression, including physical and verbal aggression and aggressive attitudes (e.g., hostility, impatience). Their analyses, they say, "revealed that multiple measures of different dimensions of aggr ressive behavior have moderate to quite large heritabilities." In addition, they say, there appears to be considerable overlap between genes associated with different types of aggression.
The researchers caution that because most of their twin pairs were female, their results may not be generalizable to males. However, their results are consistent with previous research by J.C.G. van den Oord and colleagues (see related article, Crime Times, 1995, Vol. 1, No. 3, Page 6), who studied biologically related and unrelated adoptive siblings and found that "genetic influences accounted for 70 percent of the variance of aggressive behavior." They also are consistent with studies showing a strong genetic influence on bullyi ing (see related article, Crime Times, 1999, Vol. 5, No. 3, Page 1) and conduct disorder (see related article, Crime Times, 2000, Vol. 6, No. 2, Page 5).
"Individual differences in multiple dimensions of aggression: a univariate and multivariate genetic analysis," Philip A. Vernon, Julie M. McCarthy, Andrew M. Johnson, Kerry L. Jang, and Julie Aitken Harris, Twin Research, Vol. 2, 1999, pp. 1 16-21. Address: Philip A. Vernon, Department of Psychology, University of Western Ontario, London, Ontario, Canada N6A 5C2, vernon@julian.uwo.ca.