Men's facial masculinity predicts changes in their female partners' sexual interests across the ovulatory cycle,whereas men's intelligence does not

A substantial body of work demonstrates that women's mate preferences change across the ovulatory cycle. When fertile in their cycles, women are especially attracted to masculine features (e.g., faces, voices, bodies), socially dominant behavior, and male scents associated with body symmetry and social dominance. Women may also find intelligent men particularly attractive when fertile, though findings are mixed. Related research shows that, on average, romantically-involved women report stronger sexual attraction to men other than their pair-bond partners, but not partners, when fertile, and especially when their partners lack features fertile women prefer (e.g., symmetry). In the current study, we examined whether women's patterns of sexual interests across the cycle are similarly moderated by partners' facial masculinity, facial attractiveness, and intelligence. Results revealed predicted effects of male partners’ facial masculinity but none for partners’ intelligence. Facial attractiveness may have effects, but we find no evidence that it does so independently of facial masculinity.     

Hormonal influences on women's extra-pair sexual interests: The moderating impact of partner attractiveness

Based on the idea that women are especially attracted to ancestral markers of male genetic quality when conceptive in their cycle, scholars have conjectured that increases in women's extra-pair sexual interests during the conceptive phase of the cycle are moderated by their primary partners' sexual attractiveness. Multiple studies have examined this prediction, with largely supportive but mixed results. The current study is the first to examine whether hormonal influences—thought to mediate cycle shifts—on women's extra-pair sexual interests are moderated by partner attractiveness. 213 naturally cycling, romantically involved women (181 attending multiple sessions) participated in up to four sessions over about a month. Estrogen and progesterone levels were measured multiple times across women's cycles. Male partner attractiveness moderated associations between progesterone levels (though not estrogen levels) and women's extra-pair sexual interests. A negative association between progesterone levels and extra-pair sexual interests, a composite measure, was observed for women with relatively unattractive partners. For women with relatively attractive partners, no clear association emerged. The interaction between progesterone and partner attractiveness was robust for women's interest in extra-pair sex, a component preregistered as exploratory. The interaction effect was also significant for the absolute intensity of women's extra-pair attraction (a component item referenced in the preregistration) but was non-significant for the frequency of women's extra-pair attraction relative to typical days (a composite component specified in the preregistration). These findings inform theoretical understandings of women's sexuality.     

Changes in Sleep Time and Sleep Quality across the Ovulatory Cycle as a Function of Fertility and Partner Attractiveness

Research suggests that near ovulation women tend to consume fewer calories and engage in more physical activity; they are judged to be more attractive, express greater preferences for masculine and symmetrical men, and experience increases in sexual desire for men other than their primary partners. Some of these cycle phase shifts are moderated by partner attractiveness and interpreted as strategic responses to women''s current reproductive context. The present study investigated changes in sleep across the ovulatory cycle, based on the hypothesis that changes in sleep may reflect ancestral strategic shifts of time and energy toward reproductive activities. Participants completed a 32-day daily diary in which they recorded their sleep time and quality for each day, yielding over 1,000 observations of sleep time and quality. Results indicated that, when the probability of conception was high, women partnered with less attractive men slept more, while women with more attractive partners slept less.     

Do more attractive women show stronger preferences for male facial masculinity?

Researchers have suggested that more attractive women will show stronger preferences for masculine men because such women are better placed to offset the potential costs of choosing a masculine mate. However, evidence for correlations between measures of women's own attractiveness and preferences for masculine men is mixed. Moreover, the samples used to test this hypothesis are typically relatively small. Consequently, we conducted two large-scale studies that investigated possible associations between women's preferences for facial masculinity and their own attractiveness as assessed from third-party ratings of their facial attractiveness (Study 1, N = 454, laboratory study) and self-rated attractiveness (Study 2, N = 8972, online study). Own attractiveness was positively correlated with preferences for masculine men in Study 2 (self-rated attractiveness), but not Study 1 (third-party ratings of facial attractiveness). This pattern of results is consistent with the proposal that women's beliefs about their own attractiveness, rather than their physical condition per se, underpins attractiveness-contingent masculinity preferences.     

Menstrual cycle variation in women's preferences for the scent of symmetrical men.

Evidence suggests that female sexual preferences change across the menstrual cycle. Women''s extra-pair copulations tend to occur in their most fertile period, whereas their intra-pair copulations tend to be more evenly spread out across the cycle. This pattern is consistent with women preferentially seeking men who evidence phenotypic markers of genetic benefits just before and during ovulation. This study examined whether women''s olfactory preferences for men''s scent would tend to favour the scent of more symmetrical men, most notably during the women''s fertile period. College women sniffed and rated the attractiveness of the scent of 41 T-shirts worn over a period of two nights by different men. Results indicated that normally cycling (non-pill using) women near the peak fertility of their cycle tended to prefer the scent of shirts worn by symmetrical men. Normally ovulating women at low fertility within their cycle, and women using a contraceptive pill, showed no significant preference for either symmetrical or asymmetrical men''s scent. A separate analysis revealed that, within the set of normally cycling women, individual women''s preference for symmetry correlated with their probability of conception, given the actuarial value associated with the day of the cycle they reported at the time they smelled the shirts. Potential sexual selection processes and proximate mechanisms accounting for these findings are discussed.     

Intersexual conflict across women's ovulatory cycle

A growing literature shows that the features women find particularly attractive in men vary across the ovulatory cycle. Women furthermore appear to more frequently report attraction to men other than primary partners when they are fertile in their cycle than in the infertile luteal phase. Previous studies have shown that men are more vigilant of or attentive to their primary partners during the fertile phase compared to the luteal phase. This study had several aims: First, to replicate and extend previous findings concerning men's vigilance of partners using male as well as female reports of men's behavior; second, to examine changes in women's behavior toward partners across the cycle; third, to examine ways in which women resist men's attempts to mate-guard across the cycle. Results indicate that (a) men are particularly self-assertive toward partners when their partners are fertile; (b) similarly, women are especially self-assertive toward partners when they are fertile; (c) women report engaging in more behaviors that resist male vigilance and mate guarding when they are fertile, especially in ways that are unobservable to male partners; and (d) these effects are especially strong when women themselves report greater attraction to men other than partners when they are fertile, compared to the luteal phase.     

Hormonal predictors of women's extra-pair vs. in-pair sexual attraction in natural cycles: Implications for extended sexuality

In naturally cycling women, Roney and Simmons (2013) examined hormonal correlates of their desire for sexual contact. Estradiol was positively associated, and progesterone negatively associated, with self-reported desire. The current study extended these findings by examining, within a sample of 33 naturally cycling women involved in romantic relationships, hormonal correlates of sexual attraction to or interests in specific targets: women's own primary partner or men other than women's primary partner. Women's sexual interests and hormone (estradiol, progesterone, and testosterone) levels were assessed at two different time points. Whereas estradiol levels were associated with relatively greater extra-pair sexual interests than in-pair sexual interests, progesterone levels were associated with relatively greater in-pair sexual interests. Both hormones specifically predicted in-pair sexual desire, estradiol negatively and progesterone positively. These findings have implications for understanding the function of women's extended sexuality — their sexual proceptivity and receptivity outside the fertile phase, especially during the luteal phase.     

Women's preferences for men's scents associated with testosterone and cortisol levels: Patterns across the ovulatory cycle

Women in the fertile phase of their menstrual cycle show an enhanced sexual preference for masculine expressions in behavioral, morphological and scent traits. These masculinity preferences may be associated with testosterone (T) levels in males and hence connote male quality as a sire. Thus, a scent preference of fertile-phase women for T is predicted. A recent study, however, found no evidence for this, but reported that women prefer the scent of men with high cortisol (C). That study had low power to detect the predicted effect, as well as other methodological limitations. We tested women's preferences across their ovulatory cycle for the body scent of men who varied in T and C, using a larger sample of men and methods used in research on cycle preferences for symmetry-related male body scent. Conception risk in the cycle positively predicted women's scent ratings of men's T; scent ratings of C or T × C interaction were not robustly related to conception risk. Conception risk is related positively to a preference for scent of men's symmetry. This preference is distinct from that arising from a preference for the scent of T. The male-emitted chemical(s) responsible for these preferences shifts across women's cycle remain unknown.     

Changes in salivary estradiol predict changes in women's preferences for vocal masculinity

Although many studies have reported that women's preferences for masculine physical characteristics in men change systematically during the menstrual cycle, the hormonal mechanisms underpinning these changes are currently poorly understood. Previous studies investigating the relationships between measured hormone levels and women's masculinity preferences tested only judgments of men's facial attractiveness. Results of these studies suggested that preferences for masculine characteristics in men's faces were related to either women's estradiol or testosterone levels. To investigate the hormonal correlates of within-woman variation in masculinity preferences further, here we measured 62 women's salivary estradiol, progesterone, and testosterone levels and their preferences for masculine characteristics in men's voices in five weekly test sessions. Multilevel modeling of these data showed that changes in salivary estradiol were the best predictor of changes in women's preferences for vocal masculinity. These results complement other recent research implicating estradiol in women's mate preferences, attention to courtship signals, sexual motivation, and sexual strategies, and are the first to link women's voice preferences directly to measured hormone levels.     

Menstrual cycle, trait estrogen level, and masculinity preferences in the human voice

Men with low testosterone (feminine men) invest in relationships and offspring more than men with high testosterone (masculine men). Women's attraction to testosterone dependent traits (e.g. masculine face shape) is enhanced during the late-follicular, fertile phase of the menstrual cycle. Attractive, feminine women have stronger preferences for masculine men as possible long-term partners than less attractive, masculine women. We manipulated 2 testosterone related vocal traits (voice pitch and apparent vocal-tract length) in voices to test if women prefer masculinized men's voices to feminized men's voices; masculinity preferences are enhanced at the fertile (late-follicular) menstrual cycle phase; the amount that masculinity preferences shift cyclically relates to average estrone-3-glucuronide concentration (the primary urinary metabolite of estrone, E3G). We found women displayed general masculinity preferences for men's voices; masculinity preferences were greater in the fertile (late-follicular) phase of the cycle than the non-fertile (early-follicular and luteal) phase; and this effect was most pronounced for women with low average E3G concentration. As feminine women (i.e. those with high average E3G levels) are most able to obtain investment even from masculine men, these women may not need to change their mating preference or strategy during the menstrual cycle as much as masculine women.     

Duration of oral contraceptive use predicts women's initial and subsequent subjective responses to sexual stimuli

Recent work suggests that a woman's hormonal state when first exposed to visual sexual stimuli (VSS) modulates her initial and subsequent responses to VSS. The present study investigated whether women's initial hormonal state was related to their subjective ratings of VSS, and whether this relationship differed with VSS content. We reanalyzed previously collected data from 14 naturally cycling (NC) women and 14 women taking oral contraceptives (OCs), who subjectively rated VSS at three hormonal time-points. NC women's ratings of 216 unique sexual images were collected during the menstrual, periovulatory, and luteal phases of their menstrual cycles, and OC women's ratings were collected at comparable time-points across their pill-cycles. NC women's initial hormonal state was not related to their ratings of VSS. OC women's initial hormonal state predicted their ratings of VSS with minimal contextual information and of images depicting female-to-male oral sex. Specifically, women who entered the study in the third week of their pill-cycle (OC-3 women) rated such images as less attractive at all testing sessions than did all other women. OC-3 women were also the only women to rate decontextualized VSS as unattractive at all testing sessions. These results corroborate previous studies in which women's initial hormonal state was found to predict subsequent interest in sexual stimuli. Future work, with larger samples, should more directly investigate whether OC-3 women's negative assessment of specific types of VSS reflects a reaction to the laboratory environment or a broader mechanism, wherein OC women's sexual interests decrease late in their pill-cycle.     

Women's behavioural engagement with a masculine male heightens during the fertile window: evidence for the cycle shift hypothesis

Previous research suggests that women may alter their behaviour during the fertile window of the menstrual cycle to attract a mate who has traits that indicate high-quality genes. We tested whether fertile women demonstrate greater behavioural engagement with a masculine compared to a less masculine male. The test was performed using a quiz show paradigm, in which a male host asked female participants general knowledge questions. The masculinity of the host was varied between participants. Women's performance on the quiz, as well as their romantic attraction to the host, was examined in relation to women's estimated cycle phase and host masculinity. Fertile compared to nonfertile women were more romantically attracted to the host and were faster to answer his questions, but only when he was portrayed as masculine. The results of the study are interpreted as being in keeping with Gangestad and Thornhill's cycle shift hypothesis (Menstrual cycle variation in women's preferences for the scent of symmetrical men. Proceedings of the Royal Society of London B: Biological Sciences, 1998;265:727–733. doi:10.1098/rspb.1998.03801998).     

Non-Advertized does not Mean Concealed: Body Odour Changes across the Human Menstrual Cycle

Females of a number of primate species display their fertile period by behavioural and/or morphological changes. Traditionally, the fertile period in human females has been considered to be concealed. However, this presumption has rarely been tested. One of the possible mechanisms for assessing menstrual cycle phase is through the sense of smell. In this study possible changes in odour across the menstrual cycle were investigated. Samples of body odour were acquired from 12 women (aged 19–27 yr), none of whom were using hormonal contraceptives. Samples were collected using cotton pads worn in the armpit for 24 h, from the menstrual, follicular and luteal cycle phases. Our experimental sample of 42 males (age 19–34 yr) repeatedly rated these odour samples for their intensity, pleasantness, attractiveness and femininity. Raw subjective smell ratings from each man were transformed to z‐scores. Subsequently, these z‐scores were tested by the general linear mixed‐model analysis (PROC MIXED, SAS) with the female's ID nested within the subject's ID as a random factor to account for the repeated measures of the subjects. Significant changes across the cycle were found for ratings of pleasantness [F_(2,689) = 702; p = 0.001], attractiveness [F(2,546) = 6.35; p = 0.002] and intensity [F(2,530) = 3.57; p = 0.028]. Odour from women in the follicular (i.e. fertile) phase was rated as the least intense and the most attractive. Subsequent post hoc analysis revealed significant differences in intensity, pleasantness and attractiveness between the menstrual phase and the follicular phase, and in pleasantness and attractiveness between the menstrual and luteal phases. Significant difference between the follicular and the luteal phase was found only for attractiveness. Our results suggest that men can potentially use smell as a mechanism for monitoring menstrual cycle phase in current or prospective sexual partners. Therefore, the fertile period in humans should be considered non‐advertized, rather than concealed.     

Neural activation in women in response to masculinized male faces: mediation by hormones and psychosexual factors

Women's preference for masculine faces varies with hormonal state, sociosexuality, and relationship status, but the underlying mechanisms are poorly understood. We hypothesized that hormones and psychosexual factors (sociosexuality, sexual inhibition/excitation) mediate the perception and evaluation of male faces thereby influencing women's preferences. We used functional magnetic resonance imaging to measure brain activity in 12 women as they evaluated pictures of male faces (half 30% masculinized, half 30% feminized). Participants were heterosexual women, age 23–28 years, who were not in a committed relationship and not using hormonal contraception. Women were tested during both the follicular and luteal phase of their menstrual cycle. We found five brain regions related to face and risk processing that responded more to the masculinized than to the feminized faces, including the superior temporal gyrus, precentral gyrus, posterior cingulate cortex, inferior parietal lobule, and anterior cingulate cortex. Increased activation in the anterior cingulate cortex, specifically, may indicate that women perceive masculinized faces to be both more risky and more attractive. We did not see any areas that were more strongly activated by feminized faces. Levels of activation were influenced by hormonal and psychosexual factors. The patterns of hormonally and psychosexually mediated neural activation observed may offer insight into the cognitive processes underlying women's partner preferences.     

Women's genital sexual arousal to oral versus penetrative heterosexual sex varies with menstrual cycle phase at first exposure

Reproductive-aged women show increased interest in sexual activity during the fertile phase of the menstrual cycle that can motivate sexual behavior and thereby increase the likelihood of conception. We examined whether women demonstrated greater sexual responses (subjective and genital sexual arousal) to penetrative versus oral sexual activities during the fertile versus non-fertile phases of their cycles, and whether women's arousal responses were influenced by the phase during which they were first exposed to these sexual stimuli (e.g., Slob et al., 1991; Wallen and Rupp, 2010). Twenty-two androphilic women completed two identical sexual arousal assessments in which genital responses were measured with a vaginal photoplethysmograph and their feelings of sexual arousal were recorded. Women viewed an array of 90 s films varying by couple type (female–female, male–male, female–male) and sexual activity type (oral or penetrative), during the fertile (follicular) and non-fertile (luteal) phases of their menstrual cycle, with the order of cycle phase at the first testing session counter-balanced. Women tested first in the fertile phase showed significantly greater genital arousal to female–male penetrative versus oral sex in both testing sessions, whereas self-reports of sexual arousal were not affected by cycle phase or testing order. These results contribute to a growing body of research suggesting that fertility status at first exposure to sexual stimuli has a significant effect on subsequent sexual responses to sexual stimuli, and that this effect may differ for subjective versus genital sexual arousal.     

Head Tilt and Fertility Contribute to Different Aspects of Female Facial Attractiveness

Subjective attractiveness ratings of facial portraits of women taken at the fertile phase of the menstrual cycle are higher than those of portraits of the same women taken during non‐fertile periods. As female faces tilted downward are rated as more attractive and female courtship behaviours change across the menstrual cycle, we investigated whether systematic downward tilt of women's faces during the fertile phase might be responsible for increased attractiveness ratings. In the original study (Proc. R. Soc. Lond. B, 271, 2004, S272), the fertile‐phase portrait of each woman was deemed more attractive in 56–62% of cases. When the portraits were reclassified by head pitch, the more downward‐tilted portrait was preferred in 64–73% of cases. The fertile‐phase portrait was no more likely to be the downward‐tilted one, however, suggesting that effects of fertility on attractiveness are not simply due to changes in head position. We also had these portraits rated (N = 130) for physical attractiveness and behavioural allure. Fertile‐phase portraits were rated as more physically attractive than non‐fertile portraits, while more downward‐tilted portraits were rated as more behaviourally alluring than less downward‐tilted ones. These data not only confirm reported effects of head tilt and fertility on perceived female attractiveness, but also suggest that these factors influence different components of the attractiveness percept.     

The masculinity paradox: facial masculinity and beardedness interact to determine women's ratings of men's facial attractiveness

In many species, male secondary sexual traits have evolved via female choice as they confer indirect (i.e. genetic) benefits or direct benefits such as enhanced fertility or survival. In humans, the role of men's characteristically masculine androgen‐dependent facial traits in determining men's attractiveness has presented an enduring paradox in studies of human mate preferences. Male‐typical facial features such as a pronounced brow ridge and a more robust jawline may signal underlying health, whereas beards may signal men's age and masculine social dominance. However, masculine faces are judged as more attractive for short‐term relationships over less masculine faces, whereas beards are judged as more attractive than clean‐shaven faces for long‐term relationships. Why such divergent effects occur between preferences for two sexually dimorphic traits remains unresolved. In this study, we used computer graphic manipulation to morph male faces varying in facial hair from clean‐shaven, light stubble, heavy stubble and full beards to appear more (+25% and +50%) or less (?25% and ?50%) masculine. Women (N = 8520) were assigned to treatments wherein they rated these stimuli for physical attractiveness in general, for a short‐term liaison or a long‐term relationship. Results showed a significant interaction between beardedness and masculinity on attractiveness ratings. Masculinized and, to an even greater extent, feminized faces were less attractive than unmanipulated faces when all were clean‐shaven, and stubble and beards dampened the polarizing effects of extreme masculinity and femininity. Relationship context also had effects on ratings, with facial hair enhancing long‐term, and not short‐term, attractiveness. Effects of facial masculinization appear to have been due to small differences in the relative attractiveness of each masculinity level under the three treatment conditions and not to any change in the order of their attractiveness. Our findings suggest that beardedness may be attractive when judging long‐term relationships as a signal of intrasexual formidability and the potential to provide direct benefits to females. More generally, our results hint at a divergence of signalling function, which may result in a subtle trade‐off in women's preferences, for two highly sexually dimorphic androgen‐dependent facial traits.     

The health of a nation predicts their mate preferences: cross-cultural variation in women's preferences for masculinized male faces

Recent formulations of sexual selection theory emphasize how mate choice can be affected by environmental factors, such as predation risk and resource quality. Women vary greatly in the extent to which they prefer male masculinity and this variation is hypothesized to reflect differences in how women resolve the trade-off between the costs (e.g. low investment) and benefits (e.g. healthy offspring) associated with choosing a masculine partner. A strong prediction of this trade-off theory is that women''s masculinity preferences will be stronger in cultures where poor health is particularly harmful to survival. We investigated the relationship between women''s preferences for male facial masculinity and a health index derived from World Health Organization statistics for mortality rates, life expectancies and the impact of communicable disease. Across 30 countries, masculinity preference increased as health decreased. This relationship was independent of cross-cultural differences in wealth or women''s mating strategies. These findings show non-arbitrary cross-cultural differences in facial attractiveness judgements and demonstrate the use of trade-off theory for investigating cross-cultural variation in women''s mate preferences.     

Environmental threat influences preferences for sexual dimorphism in male and female faces but not voices or dances

During evolution, humans faced the trade-off between preferences for feminine and masculine traits which are presumably connected to parental care, and genetic quality or provisioning abilities, respectively. Recent research has shown that environmental factors influence preferences for femininity/masculinity in potential mates. However, studies mainly focus on women's preferences for isolated cues in men. We examined the influence of pathogen and resource threat on women's and men's preference for femininity/masculinity in opposite sex unmanipulated faces, voices, and dances. Three hundred seventy (206 women) students, aged 18–35 years, from universities across the state of Sao Paulo, Brazil, were primed with newspaper-like articles on either pathogen threat (Aedes aegypti, and its mosquito-borne diseases) or resource threat (=economic crisis), and compared to a control-priming condition (lions poisoned in a Kenyan Reserve). Participants were randomly assigned to rate attractiveness of the stimuli in one of the mating strategies (i.e., short-term or long-term relationship context). After each priming article, participants rated attractiveness of pre-rated masculine and feminine stimuli of the opposite sex in a standalone-rating design. The environmental threats and the control-priming conditions were shown in a random sequence. We found that the environmental threat and the mating strategies had no systematic effect on preferences for faces, voices and behavior, suggesting that different modalities can cue to different individual qualities and can be used differently according to the environmental context and relationship strategy. The environmental threat only had a weak effect on preferences for facial femininity-masculinity: women found feminine male faces more attractive under pathogen threat, while men found feminine female faces more attractive under resource threat. This is in contrast to some previous studies, and shows that effect of ecological factors on human psychology should be submitted to a more rigorous scrutiny. The mating strategies only interacted with voice attractiveness: women rated male voices as more attractive after being primed with any type of environmental threat when considering long-term relationship context, while in men this was true when considering short-term relationship. Finally, feminine dance videos were perceived as attractive under environmental threat, irrespective of sex, type of environmental threat or mating strategy.     

Women's preferences for masculinity in male faces are predicted by pathogen disgust,but not by moral or sexual disgust

Because women's preferences for male masculinity reflect tradeoffs between the benefits of greater genetic health and the costs of lower paternal investment, variables that affect the importance of these costs and benefits also affect masculinity preferences. Concern about disease and pathogens may be one such variable. Here we show that disgust sensitivity in the pathogen domain is positively correlated with facial masculinity preferences, but disgust sensitivity in the moral and sexual domains is not. Our findings present novel evidence that systematic variation in women's preferences for masculine men reflects factors that influence how women resolve the tradeoff between the benefits and costs associated with choosing a masculine partner.