The Evolutionary Psychology of Extrapair Sex: The Role of Fluctuating Asymmetry

This study explored evolutionary hypotheses concerning extrapair sex (or EPCs: extrapair copulations). Based on recent notions about sexual selection, we predicted that (a) men's number of EPCs would correlate negatively with their fluctuating asymmetry, a measure of the extent to which developmental design is imprecisely expressed, and (b) men's number of times having been an EPC partner of a woman would negatively correlate with their fluctuating asymmetry. In a sample of college heterosexual couples, both hypotheses were supported. In addition, men's physical attractiveness independently predicted how often they had been an EPC partner. Women's anxious attachment style positively covaried with their number of EPC partners, whereas their avoidant attachment style negatively covaried with their number of EPC partners. © Elsevier Science Inc., 1997