Several hypotheses on the form and function of sex differences in social behaviors were tested. The results suggest that friendship preferences in both sexes can be understood in terms of perceived reciprocity potential—capacity and willingness to engage in a mutually beneficial relationship. Divergent social styles may in turn reflect trade-offs between behaviors selected to maintain large, functional coalitions in men and intimate, secure relationships in women. The findings are interpreted from a broad socio-relational framework of the types of behaviors that (...) facilitate selective advertisement and investment of reciprocity potential across individuals and within groups of men and women. (shrink)

Although facial features that are considered beautiful have been investigated across cultures using the framework of sexual selection theory, the effects of head hair on esthetic evaluations have rarely been examined from an evolutionary perspective. In the present study the effects of six hair-styles (short, medium-length, long, disheveled, knot [hair bun], unkempt) on female facial attractiveness were examined in four dimensions (femininity, youth, health, sexiness) relative to faces without visible head hair (“basic face”). Three evolutionary hypotheses were tested (covering hypothesis, (...) healthy mate theory, and good genes model); only the good genes model was supported by our data. According to this theory, individuals who can afford the high costs of long hair are those who have good phenotypic and genetic quality. In accordance with this hypothesis, we found that only long and medium-length hair had a significant positive effect on ratings of women’s attractiveness; the other hairstyles did not influence the evaluation of their physical beauty. Furthermore, these two hairstyles caused a much larger change in the dimension of health than in the rest of the dimensions. Finally, male raters considered the longer-haired female subjects’ health status better, especially if the subjects were less attractive women. The possible relationships between facial attractiveness and hair are discussed, and alternative explanations are presented. (shrink)