Social scientists generally agree that a paradigm shift has occurred over the course of the last three decades of research in human behavior: the zeitgeist has moved away from a culturally centered, social learning model towards a more balanced perspective in which both genetic and environmental factors are understood to explain the wide variations observed in human behavior. This perspective now applies in the areas of mental health and illness, as well as across several domains of normal, varying psychological constructs, such as intelligence, personality, interests, and attitudes. The study of antisocial behavior is no exception to this paradigm shift. There is now abundant evidence that both genetic and environmental influences--and probably their interaction--are of major importance in explaining individual differences in antisocial behavior, including differences in criminal behavior.
Evidence for a genetic basis of antisocial behavior stems from several different lines of research. First, behavioral genetic studies of twins and adoptees have demonstrated that heredity plays a role in antisocial behavior, including various forms of aggression and criminality, by finding greater concordance for such behavior in genetically related individuals compared to nonrelatives living in the same environment. Second, various correlates of antisocial behavior, including personality factors such as impulsivity, sensation-seeking, risk-taking, and callous-unemotional traits, are known to be at least partly genetically influenced. Third, psychiatric outcomes related to antisocial behavior, including antisocial personality disorder, gambling, and substance use and abuse, have also been investigated in genetically informative designs, and each of these has demonstrated significant genetic influence.
This paper summarizes the heritability of each of these aspects or correlates of antisocial behavior and discusses research attempting to unpack the genetic and environmental "black boxes" involved in antisocial behavior, including studies investigating the influence of both biological and social risk factors and how they might be mediated by genetic and environmental factors. Examples of biological risk factors could be neurotransmitters, physiological arousal, frontal lobe function, and hormones, while social risk factors would include socioeconomic status, peer characteristics, and parental monitoring and discipline. Biological risk factors may not necessarily be entirely genetically based, and social risk factors may not be purely environmental in origin; this highlights the complexity of the relationships between risk factors and antisocial behavior.
This paper also reports studies that have identified specific genetic associations with antisocial behavior. Yet genetic predispositions, though important, are more deleterious in the presence of adverse environments. This view dovetails with other biosocial theories of antisocial behavior in which the effects of biological risk factors have been found to be moderated by social circumstances. An overarching biosocial model of antisocial behavior is presented here, along with a discussion of a few key findings that demonstrate interactions of social and biological factors in the development of antisocial behavior.
Finally, this paper considers the implications of behavioral genetic research on antisocial behavior for understanding individual responsibility. No individual's behavior can ever be explained entirely, either in terms of genetic predispositions or in terms of cumulative experiences, and an explanation of an individual's behavior, even if it were complete, would not necessarily excuse that behavior. Even with increasing understanding of the genetic bases of human behavior, a cautious approach is warranted either in making inferences about a given individual or in considering changes to the legal system that might now take a defendant's experiences and disposition into account. …