Trevor spent the first four years of his life living with various family members and in various foster homes. Maggie, his second cousin, adopted Trevor about six months ago. Although she provides him with love, support, and stimulation, Trevor does not seem attached to her. He resists any kind of affection and prefers to be by himself rather than socialize with his new family. According to the DSM-5, Trevor probably has:

reactive attachment disorder

Explanation:

DSM-5 is the Diagnostic and Statistical Manual of Mental Disorders handbook that contains all the information and serves as an authoritative guide to the diagnosis of mental disorders. Using this handbook we can say that Trevor probably has a reactive attachment disorder. This disorder, also known as RAD is a condition in which the individual (usually a child) is unable to establish a healthy attachment with their parent or primary caretaker. Which is the case in this scenario since Trevor is unable to form a connection with Maggie even though she has always taken care of him.

as university of miami psychologists debra lieberman and adam smith pointed out in a recent article in the journal current directions in psychological science, humans have social and psychological mechanisms to deter incest. with very few exceptions, marriages between brothers and sisters and between parents and their children are verboten in every human culture. the primary psychological anti-incest mechanism is the yuck response. even the idea of sex with their mom or dad, bro or sis is upsetting to most people. the psychologist jonathan haidt has found that nearly everyone is repelled by the prospect of brother-sister sex, even in hypothetical situations in which there is no chance of pregnancy).

the biological cost of incest

this raises an interesting question: just what’s so bad about incest? sure, having sex with your dad or your sister seems gross — but why? some anthropologists have argued that incest taboos are learned social conventions. this explanation, however, doesn’t make sense to me as it does not explain the widespread existence of anti-incest mechanisms in creatures ranging from cockroaches to chimpanzees. second, the incest taboo is about as close to a universal law as human moral rules get.

why should mechanisms to avoid incest be so widespread both in nature and across human societies? the answer is simple. the problem with having sex close with relatives is that there is an astonishingly high chance that your offspring will be born with a serious birth defect.

answer; primary source information;