When you encounter an adult who has difficulty getting along with others and maintaining any relationships, you will probably be tempted to consider how he or she was treated in his or her first group.

secondary
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primary
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The answer is the primary group.

Explanation:

In a primary group, the different members usually share close, personal, as well as enduring relationships. In these groups, people usually share activities and cultural aspects. Some examples of a primary group include family or childhood friends.

The term was established by Charles Cooley through his book Social Organization: A Study of the Larger Mind. It is said that primary groups are very relevant concerning the development of personal identity.    

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.