A series of two studies published in Evolutionary Psychology examined how the characteristics of one’s current romantic partner and those of their opposite-sex friend predicts sexual interest in the opposite-sex friend for both men and women. The findings largely provided support for the mating activation hypothesis.
Opposite-sex friends can be a way of seeking intimate short- and long-term romantic relationships. This possibility suggests it can be an evolutionary adaptive strategy to start and maintain opposite-sex friendships (i.e., potential reproductive success).
Study authors Aleksandra Szymkow and Natalia Frankowska write, “if natural selection has shaped psychological mechanisms that motivate individuals to seek friendships, then we should expect a strategic search for specific friends, which additionally should be different for women and men.” Various studies suggest that forming opposite-sex friendships can be a way of gaining short term sexual access to the opposite-sex, protection, long-term mates, and even back-up mates.
Men and women may seek opposite-sex friends for the general purpose of forming friendships. However, under certain circumstances, such friendships may be for the purpose of finding a short- or long-term mate. The back-up mate hypothesis posits that cultivating potential replacement mates could have served as an effective solution for various adaptive problems (e.g., decline in partner’s mate value). In ancestral environments, lacking a back-up mate could have placed women in jeopardy in terms of being able to protect and provide resources for children. Thus, having opposite-sex friends could have served as “mate insurance.”
Prior research has observed parallels between opposite-sex friend preferences and mate preferences, with men prioritizing physical attractiveness in friends, and women prioritizing physical protection and economic resources. But these preferences are flexible, indicating their adaptive capacity; for example, “unrestricted sociosexual orientation predicted giving greater priority to physical prowess among women but not men, while being mated predicted giving higher priority to economic resources of OSF among women and lower among men.” As such, sexual interest in opposite-sex friends may be an adaptive response to cues such as environmental conditions and personal qualities, and a means for solving adaptive problems.
Study 1 included a total of 146 cross-sex pairs of friends who were in committed heterosexual relationships. The variable of interest in this study was sexual attraction toward one’s opposite-sex friend. Participants were prompted to visualize that person, and provided ratings to cognitive, affective, and behavioural items such as “I have sexual fantasies about my friend”, “Do you become sexually aroused when with your friend”, or “If your friend wanted to have a friends-with-benefits relation with you, would you agree?” on a scale of 1 (never) to 7 (very often). Predictor variables included participants’ current partner’s and opposite-sex friend’s physical attractiveness, resources, and support given. Level of overall satisfaction with the romantic relationship, length of romantic relationship and friendship were also measured.
Study 2 included 161 female heterosexual participants in committed romantic relationships who maintained a friendship with a heterosexual man. As in Study 1, the researchers assessed for sexual attraction toward an opposite-sex friend. Predictor variables included perceived financial resources of the romantic partner and friend, satisfaction with the romantic relationship, and sociosexual orientation. Sociosexual orientation refers to “participants’ attitudes about, history of, and desire for commitment-free sex.”
These studies sought to provide additional support for the mating activation hypothesis, particularly the moderating role of a current partner’s qualities, and opposite-sex friend’s qualities in shaping sexual interest in opposite-sex friends. The results revealed support for this hypothesis, such that, the physical attractiveness of one’s opposite-sex friend positively predicted sexual interest in this friend. This effect was larger in men than women. This effect was stable for men in that it was not moderated by any of the current partner’s qualities; however, for women there was flexibility depending on their current partner’s characteristics. When a woman’s partner was highly attractive, provided a high amount of support, or she was highly satisfied with her romantic relationship, the physical attractiveness of an opposite-sex friend no longer predicted sexual interest in him.
Lastly, the perceived financial resources of opposite-sex friends predicted sexual interest toward them for highly sexually unrestricted women and those in romantic relationships with high-income men.
The authors emphasize that various moderators shape men’s and women’s sexual interest in opposite-sex friends. They conclude, “Among them are qualities of one’s current partner, qualities of opposite-sex friends, as well as individual characteristics of participants. Finally, our research proves the predictive value of an evolutionary psychological approach to understanding opposite-sex friends.”
The study, “Moderators of Sexual Interest in Opposite-sex Friends”, was authored by Aleksandra Szymkow and Natalia Frankowska.
