Passion and compassion: Psychology of kin relations within and beyond the family

Family is special. People avoid sexual contact with close relatives, but at the same time are highly beneficent toward them. Such discriminatory behavior is guided by a set of psychological mechanisms, heuristics that facilitate evolutionarily adaptive behavior most of the time but may lead to over-perception of kinship under specific circumstances. In this chapter, we describe psychological mechanisms of kin recognition in sexual and altruistic contexts, and we discuss the extent to which these mechanisms may influence close relationships between unrelated individuals, resulting in an experience of “psychological kinship.” We suggest that friendship may provide a context within which over-inclusive kin recognition is especially likely to occur, especially among women. We also identify questions for future research, including when men might be especially prone to over-perceiving kinship.