Experimentally Varying Sex Ratios and Masculine Cues Affect Attitudes Towards Promiscuity and Self-Reported Mate Value.

Sex ratios influence intrasexual competition with consequences for a variety of behaviours, including social attitudes. Cues of masculinity, such as beards, are also known to respond to the local intensity of intrasexual competition. Whether different cues of intrasexual competition interact or have additive effects on behaviour remains unknown. Here we test whether attitudes concerning promiscuity and self-reported mate value are influenced by the relative numbers of women and men, and/or the frequency of bearded men. We primed subjects (men= 540, women= 522) with one of the nine possible combinations of three sex ratios (female bias 3:1; neutral 1:1; male bias 1:3) and three frequency of beards (0%; 50%; 100%) treatments. To simulate local mating market effects, participants were informed that images were of dating profiles of people ‘within 5 miles’ of them. After rating each profile for attractiveness, participants were asked to complete the wrongness of promiscuity and self-reported mate value scales. We found that men, but not women, view both male and female promiscuity more negatively when exposed to male-biased sex ratios and rate female promiscuity slightly more negatively when exposed to men with beards than clean-shaven men. The male-specific nature of these effects is consistent with anti-promiscuity attitudes functioning to promote paternity certainty rather than facilitating female-female competition for male investment. We found no evidence of self-reported mate value increasing when individuals were the rarer sex. However, there were sex differences in relative ratings of male and female promiscuity among individuals with more open sociosexual orientations, a finding relevant to the origins of sexual double standards.