lism or drug addiction. That is, where both twins exhibited antisocial behaviors, they also tended to exhibit the same antisocial behaviors. Unable to establish a genetic link, however, the study concluded, "environmental factors such as peer pressure may influence the way in which a genetic vulnerability to externalizing behaviors is expressed" (Hick, Krueger, Iacono, McGue & Patrick 1). Thus, the study concluded that while there may be a genetically transmitted vulnerability to externalizing antisocial behaviors, the manner in which this vulnerability is expressed - the particular antisocial behaviors expressed - must be the result of environmental factors. Thus, according to this study, while Kyle and Stan might share a genetic tendency to act antisocially, whether and how they act so is likely based on environmental factors.
Nonetheless, critics argue that there is, in fact, no way to identify specifically a genetic trait that controls external behaviors such as these. These critics contend that the fact that the children are raised in the same environment explains their similar behavior (Wasserman 1). The case of Kyle and Stan, therefore, seems to at least serve as an exception, if not to disprove, genetic and environmental explanations for criminal behavior. Their case, therefore, raises the question of "free will." Perhaps Kyle simply chose to act as a criminal while Stan did not.
Still, evidence from the Minnesota twin study and others forces one to consider a genetic basis for antisocial behavior. This information is of particular interests to determinists, or theorists who believe that a person's actions are essentially pre-determined by genetic, environmental and other factors outside their control. Proponents of determinism argue that human beings do not act based on free will, but rather that their actions are determined by often uncontrollable factors that make people who they are. Essentially, determinism is the vie...