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Although many researchers have suggested that more physically attractive women report less restricted sociosexual orientations (i.e., report being more willing to engage in short-term, uncommitted sexual relationships), evidence for this association is equivocal. Consequently, we tested for possible relationships between women's scores on the revised version of the Sociosexual Orientation Inventory (SOI-R) and women's body mass index (N = 212), waist-hip ratio (N = 213), ratings of their facial attractiveness (N = 226), and a composite attractiveness measure derived from these three intercorrelated measures. Our analyses suggest that more attractive women report less restricted sociosexual orientations. Moreover, we show that this link between attractiveness and sociosexual orientation is not simply a consequence of women's scores on the behavior subscale of the SOI-R. Importantly, however, the correlations between measures of women's physical attractiveness and their reported sociosexual orientation were very weak, suggesting that perceptions of these potential cues of women's sociosexual orientation are unlikely to provide accurate, socially relevant information about others during social interactions.

Findings for progesterone and anxiety in non-human animals led to the hypothesis that women's interpersonal anxiety will track changes in progesterone during the menstrual cycle. There have been few direct tests of this hypothesis, however. Consequently, we used a longitudinal design to investigate whether interpersonal anxiety (assessed using the anxious jealousy subscale of the relationship jealousy questionnaire) tracked changes in salivary steroid hormones during the menstrual cycle in a large sample of young adult women. We found no evidence for within-subject effects of progesterone, estradiol, their interaction or ratio, testosterone, or cortisol on anxious jealousy. There was some evidence that other components of jealousy (e.g., reactive jealousy) tracked changes in women's cortisol, however. Collectively, these results provide no evidence for the hypothesis that interpersonal anxiety tracks changes in progesterone during the menstrual cycle.

Summary Red facial coloration is an important social cue in many primate species, including humans. In such species, the vasodilatory effects of estradiol may cause red facial coloration to change systematically during females’ ovarian cycle. Although increased red facial coloration during estrus has been observed in female mandrills (Mandrillus sphinx) and rhesus macaques (Macaca mulatta), evidence linking primate facial color changes directly to changes in measured estradiol is lacking. Addressing this issue, we used a longitudinal design to demonstrate that red facial coloration tracks within-subject changes in women’s estradiol, but not within-subject changes in women’s progesterone or estradiol-to-progesterone ratio. Moreover, the relationship between estradiol and facial redness was observed in two independent samples of women (N = 50 and N = 65). Our results suggest that changes in facial coloration may provide cues of women’s fertility and present the first evidence for a direct link between estradiol and female facial redness in a primate species. © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The value of different mate choices may depend on the local pathogen ecology and on personal infection susceptibility: when there is a high risk of infection, choosing a healthy or immunocompetent ...

Although dominance perceptions are thought to be important for effective social interaction, their primary function is unclear. One possibility is that they simply function to identify individuals who are capable of inflicting substantial physical harm, so that the perceiver can respond to them in ways that maximize their own physical safety. Another possibility is that they are more specialized, functioning primarily to facilitate effective direct (i.e., violent) intrasexual competition for mates, particularly among men. Here we used a priming paradigm to investigate these two possibilities. Facial cues of dominance were more salient to women after they had been primed with images of angry men, a manipulation known to activate particularly strong self-protection motivations, than after they had been primed with images of angry women or smiling individuals of either sex. By contrast, dominance cues were more salient to men after they had been primed with images of women than when they had been primed with images of men (regardless of the emotional expressions displayed), a manipulation previously shown to alter men's impressions of the sex ratio of the local population. Thus, men's dominance perceptions appear to be specialized for effective direct competition for mates, while women's dominance perceptions may function to maximize their physical safety more generally. Together, our results suggest that men's and women's dominance perceptions show different patterns of context-sensitivity and, potentially, shed new light on the routes through which violence and intrasexual competition have shaped dominance perceptions.

Previous studies show that parasite prevalence and mortality/health are related to cultural variation in women's preferences for attractive and masculine traits in men. Other studies have suggested that both male–male competition and wealth may also be important correlates of cross-cultural variation in women's masculinity preferences. Here we examined whether exposure to cues of direct male–male competition, violence, or wealth influenced women's face preferences. We showed women slideshows of images with cues of low and high direct male–male competition/violence or wealth and measured their visual preferences for masculine face traits. Recent visual experience changed women's preferences for facial masculinity, with women preferring more masculine male faces after exposure to images of men engaged in direct physical competition, images of weapons, or images depicting items of high monetary value. Recent visual experience had no significant effects on preferences for masculinity in same-sex faces. Given that high levels of direct physical competition and violence among males may increase the importance of direct intra-sexual competition, it may be adaptive for women to shift visual preferences in favor of males with face cues indicating physical strength and dominance over investment in such environments. Similarly, in wealthy environments investment may be less important than other aspects of quality and so it may be adaptive for women to shift visual preferences in favor of males with face cues indicating other aspects of quality over investment. Overall, our data demonstrate that preferences can be strategically flexible according to recent visual experience and support the notion of environment contingent preferences.

Previous research has shown that men prefer higher-pitched women's voices and women prefer lower-pitched men's voices. However, both men and women can modulate their voice pitch, which can affect others' perceptions of the voice. Here we tested whether deliberate pitch changes affect speakers' vocal attractiveness. Our results suggest that deliberately exaggerating sex-typical voice pitch (i.e. lowering pitch in men and raising pitch in women) does not necessarily increase vocal attractiveness but that exaggerating sex-atypical voice pitch (i.e. raising pitch in men and lowering pitch in women) may decrease vocal attractiveness. By contrast with these findings for attractiveness, listeners interpreted lowered-pitch voices as sounding more dominant than habitually pitched voices in same-sex voices, which may aid in avoiding the costs associated with intrasexual competition. These findings suggest that the way humans perceive deliberate manipulations of voice pitch can mitigate the potential costs of using an alterable cue to assess attractiveness, and that functional honesty may only evolve in domains where such honesty would be favourable to perceivers.

Previous research suggests that sociosexual orientation and relationship status each predict women’s preferences for masculine men. However, if partnered women’s preferences primarily reflect the short-term (i.e., currently unfulfilled) aspect of a pluralistic mating strategy and unpartnered women’s preferences reflect the dominant aspect of their current mating strategy, then sociosexual orientation should predict the preferences of unpartnered women better than those of partnered women. Perceptions of other women’s attractiveness may show a similar pattern of individual differences, if such perceptions of other women’s attractiveness are important for intra-sexual competitive behavior. Consistent with these predictions, in the current study, analyses of the relationship between women’s face preferences and sociosexual orientation indicated that unpartnered women reporting greater willingness to engage in uncommitted relationships demonstrated stronger preferences for exaggerated sex-typical characteristics in men’s and women’s faces. For partnered women, no corresponding relationship between sociosexual orientation and face preferences was evident. Collectively, these findings suggest that individual differences in sociosexual orientation may be better predictors of face preferences among unpartnered women than among women whose long-term relationship goals are currently being met.

Although many women find masculine men physically attractive, the perception that such men are prone to infidelity may limit their appeal as romantic partners. To explore this issue, we first investigated the interplay between the effects of men's face shape (masculinity versus femininity) and social knowledge of men's behavior in previous romantic relationships (faithful versus unfaithful) on women's judgments of men's attractiveness. Analyses suggested that the extent to which women rated masculine men to be more attractive than feminine men was significantly greater when judging men labeled as faithful than when judging men labeled as unfaithful. In a second experiment, we obtained similar results when the women in our study were instructed to imagine they were on a date with each of the men and that, while on the date, they observed him either flirting or not flirting with another woman. These interactions suggest that social knowledge about men's behavior in romantic relationships can offset one of the costs that women associate with choosing a masculine mate, increasing the appeal of masculine men. More fundamentally, these findings suggest integration of social knowledge and information from facial cues in women's attractiveness judgments.

Sexually dimorphic characteristics in men may act as cues, advertising long-term health, dominance, and reproductive potential to prospective mates. Evolution has accordingly adapted human cognition so that women perceive sexually dimorphic facial features as important when judging the attractiveness and suitability of potential mates. Here we provide evidence showing, for the first time, that women's memory for details encountered in recently experienced episodes is also systematically biased by the presence of men's facial cues signaling enhanced or reduced sexual dimorphism. Importantly, the direction and strength of this bias are predicted by individual differences in women's preferences for masculine versus feminine facial features in men and are triggered specifically while viewing images of male but not female faces. No analogous effects were observed in male participants viewing images of feminized and masculinized women's faces despite the fact that male participants showed strong preferences for feminized facial features. These findings reveal a preference-dependent memory enhancement in women that would promote retention of information from encounters with preferred potential mates. We propose that women's memory for recently experienced episodes may therefore be functionally specialized for mate choice and in particular for the comparative evaluation of alternative potential mates. This also raises the possibility that similar specialization may be present in other species where it has been established that precursor, ‘episodic-like’ forms of memory exist.

In nonhuman species, increasing the proportion of potential mates in the local population often increases preferences for high-quality mates, while increasing the proportion of potential competitors for mates intensifies within-sex competition. In two experiments, we tested for analogous effects in humans by manipulating pictorial cues to the sex ratio of the local population and assessing women's preferences for facial symmetry, a putative cue of mate quality in humans. In both experiments, viewing slideshows with varied sex ratios tended to increase preferences for symmetry in the sex that was depicted as being in the majority and tended to decrease preferences for symmetry in the sex that was depicted as being in the minority. In other words, increasing the apparent proportion of a given sex in the local population increased the salience of facial cues of quality in that sex, which may support adaptive appraisals of both potential mates' and competitors' quality. This effect of sex ratio was independent of (i.e. did not interact with) an effect of cues to the degree of variation in the attractiveness of individuals in the local population, whereby the degree of variation in men's, but not women's, attractiveness modulated symmetry preferences. These findings demonstrate that symmetry preferences in humans are influenced by cues to the sex ratio of the local population in ways that complement both the facultative responses that have been observed in many other species and theories of both intersexual and intrasexual selection.

Effects of social learning on mate preferences have been observed in a wide range of animal species, including humans. However, it is not known whether social learning also influences other important aspects of social perception in humans. We investigated whether ‘eavesdropping’, a form of social learning whereby observers extract information about individuals’ qualities by observing their interactions with others, influences men’s perceptions of the dominance of potential rivals. We found that observing the responses of other individuals modulates the perceived dominance of aggressors. Observers rated aggressors’ dominance higher when they had previously observed others responding to the aggressor in a fearful, intimidated manner than when they had observed others responding to the aggressor in an angry, aggressive manner. By contrast with this finding for rated dominance, observing identical interactions did not affect observers’ perceptions of the trustworthiness of the aggressors. The effect of observing others’ responses on the perceived dominance of aggressors demonstrates that eavesdropping influences perceptions of dominance rank among men, which would be adaptive if it reduces the costs (e.g. risk of serious injury and/or loss of resources) that may be associated with acquiring knowledge of others’ dominance rank via exclusively self-reliant learning. While previous research on social learning and sexual selection has focused on intersexual interactions (i.e. mate choice copying effects), our findings suggest that eavesdropping may also influence sexual selection for male traits via intrasexual competition.

Reciprocity evolves only when social partners reliably repay, with interest, the investments of others. However, not all individuals are equally able—or motivated—to recompense others satisfactorily. As such, reciprocity relies greatly on the capacities and motives of partners. Apparent health may provide a cue to the value of potential exchange partners in this regard: healthier individuals will tend to live longer and accrue more, higher quality resources, thus increasing the incentives for mutual cooperation. In a monetary exchange task, we show that the apparent health of partners' faces affects human reciprocity. Specifically, participants were more willing to return a profitable amount to, but not more willing to invest in, apparently healthy than unhealthy partners. This effect appears to be a function of the attractiveness of apparent health, suggesting a preference for repayment of attractive partners. Furthermore, the effect of apparent health on reciprocal exchange is qualified by the sex of the partners, implicating a history of sexual selection in the evolution of human social exchange.

Although there is compelling evidence for associations between facial masculinity and indices of dominance in men, comparatively few studies have tested for corresponding associations in women. Here we found that (1) ratings of women’s facial masculinity were correlated with their scores on a dominance questionnaire, and (2) prototypes with the average facial characteristics of women with high scores on the dominance questionnaire were judged to be more masculine than prototypes with the average facial characteristics of women with low scores, even when color and texture cues were kept constant to control for effects of makeup use. These findings suggest an association between facial masculinity and dominance in women, complementing prior work reporting that masculine women are perceived to be more dominant than their relatively feminine peers.

Kin recognition is an essential component of kin-directed adaptive behavior. Consequently, potential mechanisms of kin recognition, such as learning a kin phenotype from family members (familial imprinting) or self (self-referential phenotype matching), have been the focus of much research. Studies using computer-manipulated self-resemblance show effects for both same-sex and opposite-sex faces and have been interpreted as evidence for self-referential phenotype matching. However, more recent research on sex-contingent face processing suggests that visual experience with faces of one sex has little influence on perceptions of faces of the other sex, calling into question how self-referential phenotype matching can influence perceptions of opposite-sex faces. Because children resemble their parents, familial imprinting could influence preferences for self-resemblance, reconciling these seemingly incompatible results for sex-contingent face processing and effects of self-resemblance on perceptions of opposite-sex faces. Here we show that women's reported emotional closeness to their father, but not mother, is positively correlated with their preferences for self-resemblance in opposite-sex, but not same-sex, individuals. These findings implicate familial imprinting in preferences for self-resemblance in opposite-sex individuals and raise the possibility that familial imprinting and self-referential phenotype matching have context-specific effects on attitudes to self-resembling individuals.

A face appears normal when it approximates the average of a population. Consequently, exposure to faces biases perceptions of subsequently viewed faces such that faces similar to those recently seen are perceived as more normal. Simultaneously inducing such aftereffects in opposite directions for two groups of faces indicates somewhat discrete representations for those groups. Here we examine how labelling influences the perception of category in faces differing in colour. We show category-contingent aftereffects following exposure to faces differing in eye spacing (wide versus narrow) for blue versus red faces when such groups are consistently labelled with socially meaningful labels (Extravert versus Introvert; Soldier versus Builder). Category-contingent aftereffects were not seen using identical methodology when labels were not meaningful or were absent. These data suggest that human representations of faces can be rapidly tuned to code for meaningful social categories and that such tuning requires both a label and an associated visual difference. Results highlight the flexibility of the cognitive visual system to discriminate categories even in adulthood.

Masculine facial characteristics are associated with indices of men's dominance. Previous research found that shorter men were more likely to attribute high dominance to masculine men, suggesting that dominant men are less sensitive to cues of dominance in other men than relatively subordinate men are. In the current study, we tested for novel evidence for this hypothesis. We observed a negative correlation between men's own dominance, assessed using the dominance subscale of the international personality items pool, and the extent to which they attributed dominance to masculine male, but not female, faces. Such variation in dominance perception supports the proposal that less dominant men are more sensitive to cues of dominance in other men and may be adaptive if less dominant men incur greater costs if they incorrectly perceive the dominance of male rivals.

Previous studies demonstrate that the extent to which individuals display exaggerated sex-typical physical characteristics is positively correlated with the extent to which they prefer sexually dimorphic physical characteristics in opposite-sex individuals. It is unclear, however, whether individual differences in sex-typical psychological traits predict variation in mate preferences in a similar manner. To investigate this issue, we examined the relationship between the sex-typical psychological traits empathizing and systemizing and the strength of participants’ preferences for sexually dimorphic shape cues in own- and opposite-sex faces. Women’s empathizing scores were positively correlated with the strength of their preferences for masculine men and men’s systemizing scores were positively correlated with the strength of their preferences for feminine women. By contrast with these findings for opposite-sex faces, neither empathizing nor systemizing scores predicted men’s or women’s preferences for sexually dimorphic cues in own-sex faces. Collectively, these findings suggest that sex-typical psychological traits have effects on attractiveness judgments that are strikingly similar to those previously reported for sex-typical physical characteristics and, potentially, implicate individual differences in empathizing and systemizing in variation in mate preferences.

Although researchers have suggested that adult women who experienced early puberty may demonstrate particularly strong preferences for masculine men, evidence for such an association is equivocal. Here we show that adult women’s preferences for masculinized male voices (i.e., male voices with lowered pitch) are negatively associated with the age at which they experienced first menses (i.e., age at menarche). Moreover, this relationship was independent of women’s stated preference for long- versus short-term relationships, suggesting that the relationship does not necessarily reflect individual differences in women’s preferred type of relationship. We discuss alternative mechanisms for the relationship between early puberty and women’s masculinity preferences, focusing on the possibility that girls who experience early puberty might learn to associate masculinity with desirable mates because of exposure to particularly masculine males during adolescence.

Women's preferences for masculine characteristics in men's voices and men's preferences for feminine characteristics in women's voices are thought to reflect adaptations that identify high-quality (e.g. healthy) mates. Consistent with this proposal, we found that men had stronger preferences than women for women's voices with raised pitch (i.e. feminized female voices) and that women had stronger preferences than men for men's voices with lowered pitch (i.e. masculinized male voices). Importantly, however, no such opposite-sex bias was evident for attributions of dominance to voices with raised and lowered pitch; men's and women's voices with lowered pitch were perceived to be more dominant than those with raised pitch and these effects were equivalent for male and female listeners. Collectively, our findings suggest that preferences for voice pitch may function, at least in part, to identify high-quality mates and show that opposite-sex biases in preferences for voice pitch cannot be explained simply by greater general sensitivity to manipulated pitch in opposite-sex voices than in own-sex voices.

Exposure to a particular population of faces can increase ratings of the normality and attractiveness of similar-looking faces. Such exposure can also refine the perceived boundaries of that face population, such that other faces are more readily perceived as dissimilar. We predicted that relatively less exposure to opposite-sex faces, as experienced by children at single-sex compared with mixed-sex schools, would decrease ratings of the attractiveness of sexual dimorphism in opposite-sex faces (that is, boys at single-sex schools would show a decreased preference for feminised faces, and girls at single-sex schools would show a decreased preference for masculinised faces). Consistent with this prediction, girls at single-sex compared with mixed-sex schools demonstrated significantly stronger preferences for facial femininity in both male and female faces. Boys at single-sex compared with mixed-sex schools demonstrated marginally stronger preferences for facial masculinity in male faces, but did not differ in their ratings of female faces. These effects were attenuated among some single-sex school pupils by the presence of adolescent opposite-sex siblings. These data add to the evidence that long-term exposure to a particular face population can influence judgements of other faces, and contribute to our understanding of the factors leading to individual differences in face preferences.

Recent studies show that subtle cues of observation affect cooperation even when anonymity is explicitly assured. For instance, recent studies have shown that the presence of eyes increases cooperation on social economic tasks. Here, we tested the effects of cues of observation on trusting behavior in a two-player Trust game and the extent to which these effects are qualified by participants' own attractiveness. Although explicit cues of being observed (i.e., when participants were informed that the other player would see their face) tended to increase trusting behavior, this effect was qualified by the participants' other-rated attractiveness (estimated from third-party ratings of face photographs). Participants' own physical attractiveness was positively correlated with the extent to which they trusted others more when they believed they could be seen than when they believed they could not be seen. This interaction between cues of observation and own attractiveness suggests context dependence of trusting behavior that is sensitive to whether and how others react to one's physical appearance.

Studies show that attractive women demonstrate stronger preferences for masculine men than relatively unattractive women do. Such condition-dependent preferences may occur because attractive women can more easily offset the costs associated with choosing a masculine partner, such as lack of commitment and less interest in parenting. Alternatively, if masculine men display negative characteristics less to attractive women than to unattractive women, attractive women may perceive masculine men to have more positive personality traits than relatively unattractive women do. We examined how two indices of women’s attractiveness, body mass index (BMI) and waist–hip ratio (WHR), relate to perceptions of both the attractiveness and trustworthiness of masculinized versus feminized male faces. Consistent with previous studies, women with a low (attractive) WHR had stronger preferences for masculine male faces than did women with a relatively high (unattractive) WHR. This relationship remained significant when controlling for possible effects of BMI. Neither WHR nor BMI predicted perceptions of trustworthiness. These findings present converging evidence for condition-dependent mate preferences in women and suggest that such preferences do not reflect individual differences in the extent to which pro-social traits are ascribed to feminine versus masculine men.

Many studies have shown that women's judgments of men's attractiveness are affected by changes in levels of sex hormones. However, no studies have tested for associations between changes in levels of sex hormones and men's judgments of women's attractiveness. To investigate this issue, we compared men's attractiveness judgments of feminized and masculinized women's and men's faces in test sessions where salivary testosterone was high and test sessions where salivary testosterone was relatively low. Men reported stronger attraction to femininity in women's faces in test sessions where salivary testosterone was high than in test sessions where salivary testosterone was low. This effect was found to be specific to judgments of opposite-sex faces. The strength of men's reported attraction to femininity in men's faces did not differ between high and low testosterone test sessions, suggesting that the effect of testosterone that we observed for judgments of women's faces was not due to a general response bias. Collectively, these findings suggest that changes in testosterone levels contribute to the strength of men's reported attraction to femininity in women's faces and complement previous findings showing that testosterone modulates men's interest in sexual stimuli.

Masculine physical traits may signal men’s underlying health and are associated with indices of men’s reproductive fitness. Here we show that preferences for low (i.e. masculine) pitch in men’s voices are positively related to self-rated attractiveness among women who are not using hormonal contraceptives. This relationship between masculinity preferences and self-rated attractiveness was evident when women judged the attractiveness of men’s voices that were played forward, but was not present when women judged the attractiveness of men’s voices that had been reversed. This variation in women’s preferences for masculinized men’s voices complements previous studies showing positive relationships between preferences for masculinity in men’s faces and women’s self-rated attractiveness and may be adaptive if attractive women are better able to attract and/or retain masculine mates. Interestingly, we observed no significant relationships between preferences for masculinized men’s voices and self-rated attractiveness among women using hormonal contraceptives. These latter null findings are consistent with previous studies in which potentially adaptive variation in masculinity preferences were also absent among women using hormonal contraceptives.

Previous studies have reported variation in women's preferences for masculinity in men's faces and voices. Women show consistent preferences for vocal masculinity, but highly variable preferences for facial masculinity. Within individuals, men with attractive voices tend to have attractive faces, suggesting common information may be conveyed by these cues. Here we tested whether men and women with particularly strong preferences for male vocal masculinity also have stronger preferences for male facial masculinity. We found that masculinity preferences were positively correlated across modalities. We also investigated potential influences on these relationships between face and voice preferences. Women using oral contraceptives showed weaker facial and vocal masculinity preferences and weaker associations between masculinity preferences across modalities than women not using oral contraceptives. Collectively, these results suggest that men's faces and voices may reveal common information about the masculinity of the sender, and that these multiple quality cues could be used in conjunction by the perceiver in order to determine the overall quality of individuals.

In nonhuman animals, mate-choice copying has received much attention, with studies demonstrating that females tend to copy the choices of other females for specific males. Here we show, for both men and women, that pairing with an attractive partner increases the attractiveness of opposite-sex faces for long-term relationship decisions but not short-term decisions. Our study therefore shows social transmission of face preference in humans, which may have important consequences for the evolution of human traits. Our study also highlights the flexibility of human mate choice and suggests that, for humans, learning about nonphysical traits that are important to pair-bonding drives copying-like behavior.

Exposure to faces biases perceptions of subsequently viewed faces such that normality judgments of similar faces are increased. Simultaneously inducing such an aftereffect in opposite directions for two groups of faces might indicate discrete responding of the neural populations coding for those groups. Here we show such "category contingent" aftereffects following exposure to faces differing in eye-spacing (wide versus narrow) for European versus African faces, adult versus infant faces, and human versus monkey faces. As aftereffects reflect changes in responses of neural populations that code faces, our results may then suggest that functionally distinct neural populations code faces of different ages, races and species and that the human brain potentially contains discrete representations of these categories.

Relatedness is a cornerstone of the evolution of social behavior. In the human lineage, the existence of cooperative kin networks was likely a critical stepping stone in the evolution of modern social complexity. Here we report the results of the first experimental manipulation of a putative cue of human kinship (facial self-resemblance) among ostensible players in a variant of the “tragedy of the commons,” the one-shot public goods game, in which group-level cooperation—via contributions made to the public good and the punishment of free riders—is supported at a personal cost. In accordance with theoretical predictions, contributions increased as a function of the “kin density” of the group. Moreover, the distribution of punishment was not contingent on kin density level. Our findings indicate that the presence of a subtle cue of genealogical relatedness facilitates group cooperation, supporting the hypothesis that the mechanisms fostering contemporary sociality took root in extended family networks.

Reported sex drive was recently found to be positively associated with heterosexual women's attraction to both men and women (Lippa, 2006). This finding was interpreted as evidence that sex drive is a generalized energizer of women's sexual behaviors and responses, rather than energizing behavior and responses towards potential mates only. Here we show that reported sex drive is positively associated with heterosexual women's preferences for sexual dimorphism in both men's and women's faces (Studies 1 and 2). These findings complement those reported by Lippa (2006), since our own studies and Lippa's show that sex drive is positively associated with heterosexual women's judgments of both men and women. Our findings for associations between reported sex drive and women's preferences for sexual dimorphism implicate sex drive as a possible source of individual differences in women's face preferences and present novel converging evidence that sex drive is a generalized energizer of women's sexual behaviors and responses.

Findings from previous studies suggest that only men who are in good physical condition can afford to pursue high-risk activities and that men who engage in high-risk activities are considered particularly attractive by women. Here, we show that men's interest in high-sensation activities, a personality trait that is known to increase the likelihood of those individuals engaging in high-risk behaviors, is positively related to the strength of their preferences for femininity in women's faces (Studies 1–3) but is not related to the strength of their preferences for femininity in men's faces (Study 2). We discuss these findings as evidence for potentially adaptive condition-dependent mate preferences, whereby men who exhibit signals of high quality demonstrate particularly strong preferences for facial cues of reproductive and medical health in potential mates because they are more likely than lower-quality men to succeed in acquiring such partners.

Although previous studies of individual differences in preferences for masculinity in male faces have typically emphasized the importance of factors such as changes in levels of sex hormones during the menstrual cycle, other research has demonstrated that recent visual experience with faces also influences preferences for sexual dimorphism in faces. Adaptation to either masculine or feminine faces increases preferences for novel faces that are similar to those that were recently seen. Here, we replicate this effect and demonstrate that adaptation to masculine or feminine faces also influences the extent to which masculine faces are perceived as trustworthy. These adaptation effects may reflect a proximate mechanism that contributes to the development of face preferences within individuals, underpins phenomena such as imprinting-like effects and condition-dependent face preferences, and shapes personality attributions to faces that play an important role in romantic partner and associate choices. Furthermore, our findings also support the proposal that visual exposure alone cannot explain the context specificity of attitudes to self-resemblance in faces.

Previous studies of changes in women's behavior during the menstrual cycle have offered insight into the motivations underpinning women's preferences for social cues associated with possible direct benefits (e.g., investment, low risk of infection) and indirect benefits (e.g., offspring viability). Here we sought to extend this work by testing for systematic variation in women's preferences for male and female faces and in their attitudes to their romantic relationship during the menstrual cycle. In Study 1, we found partnered women's reported commitment to their romantic relationship and preferences for femininity in male and female faces were strongest on days of the menstrual cycle when progesterone levels are increased (and fertility is low). Happiness in relationships did not change across the cycle. In Study 2, we found that the effect of cycle phase on women's preference for feminine faces was independent of increased attraction to apparent health in faces during the luteal phase. Collectively, these findings are further evidence that women's preferences for social cues associated with possible direct benefits and commitment to relationships are strongest during conditions characterized by raised progesterone level, while attraction to men displaying cues associated with possible indirect benefits is strongest when women are most fertile.

The attractiveness of women's faces, voices, bodies, and odors appear to be interrelated, suggesting that they reflect a common trait such as femininity. We invoked novel approaches to test the interrelationships between female vocal and facial attractiveness and femininity. In Study 1, we examined the relationship between facial-metric femininity and voice pitch in two female populations. In both populations, facial-metric femininity correlated positively with pitch of voice. In Study 2, we constructed facial averages from two populations of women with low- and high-pitched voices and determined men's preferences for resulting prototypes. Men preferred averaged faces of women from both populations with higher pitched voices to those with lower pitched voices. In Study 3, we tested whether the findings from Study 2 also extended to the natural faces that made up the prototypes. Indeed, men and women preferred real faces of women with high-pitched voices to those with low-pitched voices. Because multiple cues to femininity are related, and feminine women may have greater reproductive fitness than do relatively masculine women, male preferences for multiple cues to femininity are potentially adaptive.

Two lines of reasoning predict that women's preferences for people exhibiting cues to kinship will be lower in the follicular phase than in the luteal phase of the menstrual cycle. Women may avoid kinship cues during the follicular phase when they are most fertile due to the costs of inbreeding. Alternatively, women may seek kinship cues during the luteal phase as a byproduct of the benefits of associating with kin during pregnancy, which is also characterized by high progesterone. We find that preferences for facial resemblance, a putative kinship cue, follow this predicted pattern and are positively correlated with estimated progesterone levels based on cycle day. Neither estimated estrogen levels nor conception risk predicted preferences for self-resemblance, and the cyclic shift was stronger for preferences for female faces than male faces. These findings lead to the possibility that this cyclic change in preference for self-resemblance may be a byproduct of a hormonal mechanism for increasing affiliative behavior toward kin during pregnancy rather than a mechanism for preventing inbreeding during fertile periods.

Platek et al. [Evol. Hum. Behav. 23 (2002) 159; 24 (2003) 81] reported that facial resemblance between self and a child increases professed willingness to invest in that child, and does so much more for men than for women. Because facial resemblance is a possible cue of kinship, and men, unlike women, can be mistaken about parenthood, Platek et al. predicted and interpreted this sex difference as an adaptation whereby men allocate parental investment in proportion to cues of the likelihood of paternity. Extending their approach using a more realistic technique for manipulating facial resemblance and eliminating some of the confounds in their methodology, In the current study, I found that facial resemblance increased attractiveness judgments and hypothetical investment decisions, although the published sex difference was not found. This could not be explained by differences in resemblance between the participants and the morphed images because a separate group of participants could match the original adult images to the new morphs with slightly (but not significantly) greater accuracy than to morphs made using Platek et al.'s method. In addition, composite scores indicating positive regard toward an image were correlated with resemblance as judged by independent observers.

Extraversion is positively associated with various indices of women’s mate quality (e.g., facial symmetry and attractiveness). Since such indices are thought to predict variation in women’s preferences for masculine men, we investigated the relationships between each of the ‘Big 5’ personality factors and women’s preferences for facial masculinity. Extraversion, but not the other four personality factors, was positively correlated with women’s preferences for masculinity in men’s, but not women’s, faces. Additionally, extraversion mediated the positive relationship between women’s self-rated attractiveness and their preferences for masculinity in men’s faces, suggesting that extraversion may play a role in condition-dependent mate preferences. Unexpectedly, openness to experience was associated with women’s preferences for femininity in faces of both sexes and this association was independent of that between extraversion and women’s preferences for masculine men. This is the first study that we know of to implicate personality traits in individual differences in women’s preferences for masculine men.