Degree of antisocial behavior is a quantitative trait in human males. Avshalon Caspi and c...

Degree of antisocial behavior is a quantitative trait in human males. Avshalon Caspi and colleagues (2002) used data on several hundred men to investigate the relationship between antisocial behavior and two factors. The first factor was genotype at the locus that encodes the enzyme monoamine oxidase A (MAOA). MAOA acts in the brain, where it breaks down a variety of the neurotransmitters nerve cells use to communicate with each other. The gene for MAOA is located on the X chromosome. Due to genetic differences in the gene’s promoter, some men have low MAOA activity and others have high MAOA activity. The second factor was the experience of maltreatment during childhood. Based on a variety of evidence, the researchers determined whether each man had experienced no maltreatment, probable maltreatment, or severe maltreatment. The data are summarized in Figure.

Figure Degree of antisocial behavior among men with different levels of MAOA activity as a function of childhood maltreatment From Caspi, et al. (2002).

a. Is the variation among men in antisocial behavior at least partly due to differences in genotype? Explain.

b. Is the variation among men in antisocial behavior at least partly due to differences in environment? Explain.

c. Do men with different genotypes respond the same way to changes in the environment? Explain.

d. Is antisocial behavior heritable? Explain.

e. Do these data influence your opinion about how men who exhibit antisocial behavior should be treated and/or punished?