Robert P. Burriss

Preferences for masculinity in male bodies change across the menstrual cycle.

In human females cyclic shifts in preference have been documented for odour and physical and behavioral male traits. Women prefer the smell of dominant males, more masculine male faces and men behaving more dominantly when at peak fertility than at other times in their menstrual cycle. Here we examine variation in preferences for body sexual dimorphism. Across two studies, both between- and within-participant, we show that women prefer greater masculinity in male bodies at times when their fertility is likely highest, in the follicular phase of their cycle. Shifts were seen when rating for a short-term but not when rating for a long-term relationship. In line with studies showing similar effects for facial sexual dimorphism, we also show that women prefer greater masculinity when they think themselves attractive than when they think themselves less attractive. These results indicate that womens preferences for sexual dimorphism in male bodies follow a similar pattern as found for sexual dimorphism and dominance in other domains and such differences in preference may serve a similar function. Cyclic preferences could influence women to select partners when most likely to become pregnant that possess traits that may be most likely to maximize their offsprings quality via attraction to masculinity or serve to help acquire investment via attraction to femininity.

Social transmission of face preferences among humans

Previous studies demonstrating mate choice copying effects among females in non-human species have led many researchers to propose that social transmission of mate preferences may influence sexual selection for male traits. Although it has been suggested that social transmission may also influence mate preferences in humans, there is little empirical support for such effects. Here, we show that observing other women with smiling (i.e. positive) expressions looking at male faces increased womens preferences for those men to a greater extent than did observing women with neutral (i.e. relatively negative) expressions looking at male faces. By contrast, the reverse was true for male participants (i.e. observing women with neutral expressions looking at male faces increased male participants preferences for those men to a greater extent than did observing women smiling at male faces). This latter finding suggests that within-sex competition promotes negative attitudes among men towards other men who are the target of positive social interest from women. Our findings demonstrate that social transmission of face preferences influences judgments of mens attractiveness, potentially demonstrating a mechanism for social transmission of mate preferences.

Sexual Orientation and the Second to Fourth Finger Length Ratio: A Meta-Analysis in Men and Women

The ratio of the lengths of the second and fourth fingers (2D:4D) may serve as a marker for prenatal androgen signaling. Because people are typically unaware of their 2D:4D, its use allows possible effects of early sex hormone regimes and socialization to be disentangled. We conducted a meta-analysis on relationships between 2D:4D and sexual orientation in men and women in 18 independent samples of men and 16 independent samples of women. Collectively, these samples comprised 1,618 heterosexual men, 1,693 heterosexual women, 1,503 gay men, and 1,014 lesbians. In addition to identifying the normative heterosexual sex difference in 2D:4D for both hands, we found that heterosexual women had higher (more feminine) left- and right-hand 2D:4D than did lesbians, but we found no difference between heterosexual and gay men. Moderator analyses suggested that ethnicity explained some between-studies variation in men. These results add to a literature suggesting that early sex hormone signaling affects sexual orientation in women, and highlight the need for further research exploring the relationships among 2D:4D, sexual orientation, and ethnicity in men.

Women's attractiveness changes with estradiol and progesterone across the ovulatory cycle

In many species, females are more sexually attractive to males near ovulation. Some evidence suggests a similar pattern in humans, but methodological limitations prohibit firm conclusions at present, and information on physiological mechanisms underlying any such pattern is lacking. In 202 normally-cycling women, we explored whether womens attractiveness changed over the cycle as a function of two likely candidates for mediating these changes: estradiol and progesterone. We scheduled women to attend one session during the late follicular phase and another during the mid-luteal phase. At each session, facial photographs, voice recordings and saliva samples were collected. All photographs and voice recordings were subsequently rated by men for attractiveness and by women for flirtatiousness and attractiveness to men. Saliva samples were assayed for estradiol and progesterone. We found that progesterone and its interaction with estradiol negatively predicted vocal attractiveness and overall (facial plus vocal) attractiveness to men. Progesterone also negatively predicted womens facial attractiveness to men and female-rated facial attractiveness, facial flirtatiousness and vocal attractiveness, but not female-rated vocal flirtatiousness. These results strongly suggest a pattern of increased attractiveness during peak fertility in the menstrual cycle and implicate estradiol and progesterone in driving these changes.

Salivary testosterone does not predict mental rotation performance in men or women

Multiple studies report relationships between circulating androgens and performance on sexually differentiated spatial cognitive tasks in human adults, yet other studies find no such relationships. Relatively small sample sizes are a likely source of some of these discrepancies. The present study thus tests for activational effects of testosterone (T) using a within-participants design by examining relationships between diurnal fluctuations in salivary T and performance on a male-biased spatial cognitive task (Mental Rotation Task) in the largest sample yet collected: 160 women and 177 men. T concentrations were unrelated to within-sex variation in mental rotation performance in both sexes. Further, between-session learning-related changes in performance were unrelated to T levels, and circadian changes in T were unrelated to changes in spatial performance in either sex. These results suggest that circulating T does not contribute substantially to sex differences in spatial ability in young men and women. By elimination, the contribution of androgens to sex differences in human performance on these tasks may be limited to earlier, organizational periods.

Oral contraceptive use in women changes preferences for male facial masculinity and is associated with partner facial masculinity

Millions of women use hormonal contraception and it has been suggested that such use may alter mate preferences. To examine the impact of oral contraceptive (pill) use on preferences, we tested for within-subject changes in preferences for masculine faces in women initiating pill use. Between two sessions, initiation of pill use significantly decreased womens preferences for male facial masculinity but did not influence preferences for same-sex faces. To test whether altered preference during pill use influences actual partner choice, we examined facial characteristics in 170 age-matched male partners of women who reported having either been using or not using the pill when the partnership was formed. Both facial measurements and perceptual judgements demonstrated that partners of women who used the pill during mate choice have less masculine faces than partners of women who did not use hormonal contraception at this time. Our data (A) provide the first experimental evidence that initiation of pill use in women causes changes in facial preferences and (B) documents downstream effects of these changes on real-life partner selection. Given that hormonal contraceptive use is widespread, effects of pill use on the processes of partner formation have important implications for relationship stability and may have other biologically relevant consequences.

Relationship satisfaction and outcome in women who meet their partner while using oral contraception

Hormonal variation over the menstrual cycle alters womens preferences for phenotypic indicators of mens genetic or parental quality. Hormonal contraceptives suppress these shifts, inducing different mate preference patterns among users and non-users. This raises the possibility that women using oral contraception (OC) choose different partners than they would do otherwise but, to date, we know neither whether these laboratory-measured effects are sufficient to exert real-world consequences, nor what these consequences would be. Here, we test for differences in relationship quality and survival between women who were using or not using OC when they chose the partner who fathered their first child. Women who used OC scored lower on measures of sexual satisfaction and partner attraction, experienced increasing sexual dissatisfaction during the relationship, and were more likely to be the one to initiate an eventual separation if it occurred. However, the same women were more satisfied with their partners paternal provision, and thus had longer relationships and were less likely to separate. These effects are congruent with evolutionary predictions based on cyclical preference shifts. Our results demonstrate that widespread use of hormonal contraception may contribute to relationship outcome, with implications for human reproductive behaviour, family cohesion and quality of life.

Hormonal contraceptive use and mate retention behavior in women and their male partners.

Female hormonal contraceptive use has been associated with a variety of physical and psychological side effects. Women who use hormonal contraceptives report more intense affective responses to partner infidelity and greater overall sexual jealousy than women not using hormonal contraceptives. Recently, researchers have found that using hormonal contraceptives with higher levels of synthetic estradiol, but not progestin, is associated with significantly higher levels of self-reported jealousy in women. Here, we extend these findings by examining the relationship between mate retention behavior in heterosexual women and their male partners and womens use of hormonal contraceptives. We find that women using hormonal contraceptives report more frequent use of mate retention tactics, specifically behaviors directed toward their partners (i.e., intersexual manipulations). Men partnered with women using hormonal contraceptives also report more frequent mate retention behavior, although this relationship may be confounded by relationship satisfaction. Additionally, among women using hormonal contraceptives, the dose of synthetic estradiol, but not of synthetic progesterone, positively predicts mate retention behavior frequency. These findings demonstrate how hormonal contraceptive use may influence behavior that directly affects the quality of romantic relationships as perceived by both female and male partners.

Face, body and speech cues independently predict judgments of attractiveness

Abstract Research on human attraction frequently makes use of single-modality stimuli such as neutral-expression facial photographs as proxy indicators of an individuals attractiveness. However, we know little about how judgments of these single-modality stimuli correspond to judgments of stimuli that incorporate multi-modal cues of face, body and speech. In the present study, ratings of attractiveness judged from videos of participants introducing themselves were independently predicted by judgments of the participants facial attractiveness (a neutral-expression facial photograph masked to conceal the hairstyle), body attractiveness (a photograph of the upper body), and speech attractiveness (the soundtrack to the video). We also found that ratings of the face, body and speech were positively related to each other. Our results support the assumption that the single-modality stimuli used in much attractiveness research are valid proxy indicators of overall attractiveness in ecologically valid contexts, ...

Sexual selection on male vocal fundamental frequency in humans and other anthropoids

In many primates, including humans, the vocalizations of males and females differ dramatically, with male vocalizations and vocal anatomy often seeming to exaggerate apparent body size. These traits may be favoured by sexual selection because low-frequency male vocalizations intimidate rivals and/or attract females, but this hypothesis has not been systematically tested across primates, nor is it clear why competitors and potential mates should attend to vocalization frequencies. Here we show across anthropoids that sexual dimorphism in fundamental frequency (F0) increased during evolutionary transitions towards polygyny, and decreased during transitions towards monogamy. Surprisingly, humans exhibit greater F0 sexual dimorphism than any other ape. We also show that low-F0 vocalizations predict perceptions of mens dominance and attractiveness, and predict hormone profiles (low cortisol and high testosterone) related to immune function. These results suggest that low male F0 signals condition to competitors and mates, and evolved in male anthropoids in response to the intensity of mating competition.