Understanding and Preventing Violence, Volume 2: Biobehavioral Influences (1994)
Chapter: STUDIES OF ANIMALS
to assess the role of genetics in violent offending, and two of the three produced nonsignificant results.
These findings suggest at most a weak role for heredity in violent behavior. But studies that use samples at high risk for violent behavior or that measure violent behavior through self-reports rather than arrest records may yet discover genetic relationships that have so far remained hidden—or underestimated—because arrests for violent offenses are rare in samples of the general population. One positive lead is the correlation between violence in biological parents and alcohol abuse in adopted-away sons. This suggests a genetic relationship between the two, an important link given the well-established correlation between alcohol and violent behavior as discussed below (see Miczek et al., Volume 3). Because many violent offenders also commit nonviolent offenses, heritability for criminality per se provides another possible link between genes and violence. Finally and perhaps most importantly, the gene-environment interaction reported for antisocial behavior (Cloninger et al., 1982; Cadoret et al., 1983) may also extend to violence.
The principles of quantitative genetics raise strong cautions about the extrapolation of empirical research findings on violence. First, evidence for the heritability of individual differences within a population cannot be used to explain average differences between populations or even within the same population over time. It is unlikely that genetic differences could account for anything but a small fraction of the change in violence over the twentieth century, differences in violent crimes among nations, or variance in rates among certain subgroups within a nation. Second, heritability cannot predict or explain an individual's culpability in a particular violent event. Third, many estimates of heritability are based on data from the Scandinavian countries, where the necessary data are routinely collected in national registries. Because the environmental variance relevant to violence may not be the same in the Scandinavian countries and in the United States, for example, the heritability estimates cannot be readily extrapolated.
STUDIES OF ANIMALS
A large number of strain comparisons and the successful establishment of selected lines demonstrate significant heritability for rodent aggression (Ebert and Sawyer, 1980; Lagerspetz and Lagerspetz, 1975; Scott, 1942, 1966; van Oortmerssen and Bakker,
