se and Alcoholism (in Evidence, 1993).
Although the evidence is sparse so far for such a genetic link to aggression, it makes sense biologically because the MAOA enzymes affected by the genetic defect breakdown the neurotransmitters of the "flight or fight" response which, if they accumulate abnormally, could stimulate aggressive tendencies (Evidence, 1993). Researchers caution that so far the genetic defect has only been demonstrated in the one Dutch family, and it is difficult to generalize the information to the population at large.
There is a lot of evidence for the effects of testosterone on aggressive behavior in both males and females (Archer, 1991; Fishbein, 1992). Higher blood testosterone levels have been found in prisoners with histories of violent behavior than in prisoners convicted of non-violent crimes (Archer, 1991). Similar results have been found when looking at adolescent repeat offenders. Although most such studies have been carried out on males, similar results have been found when looking at female violent offenders: they also showed higher testosterone levels than females committing non-violent offenses.
Aggression is an adaptive response to external events, but while both sexes are capable of aggression, the aggressive behavior of males and females differs because of innate differences in biological processes (Fishbein, 1992). The aggressive response is due to an interaction between hormones and neurotransmitters. During development in utero, testosterone is produced around the seventh week and this begins the differentiation into a male or a female fetus, and leads to different neuroanatomical features. In both sexes, the right hemisphere develops more rapidly than the left, and in males the left develops later than in females. The role of hormones in the design of the neurochemical system leads to subtle differences in emotional behavior in males and females, such as their susceptibility to a...