Are attractive men's faces masculine or feminine? The importance of controlling confounds in face stimuli

Women's preferences for male masculinity are highly variable. Although many researchers explain this variability as reflecting systematic individual differences in how women resolve the tradeoff between the costs and benefits of choosing a masculine partner, others suggest that methodological differences between studies are responsible. A recent study found general femininity preferences for judgments of faces that were manipulated in sexual dimorphism of shape but general masculinity preferences for judgments of faces that were based on perceived masculinity. Using the original stimuli, we replicated these previous results but found equivalent general femininity preferences for both types of faces when nonface confounds in the stimuli (e.g. hairstyle) were eliminated through masking. We conclude that care must be taken to control potential confounds in stimuli and that the influence of nonface cues on preferences for facial masculinity deserves further study.

Correlated male preferences for femininity in female faces and voices

Sexually dimorphic physical traits are important for mate choice and mate preference in many species, including humans. Several previous studies have observed that women's preferences for physical cues of male masculinity in different domains (e.g., visual and vocal) are correlated. These correlations demonstrate systematic, rather than arbitrary, variation in women's preferences for masculine men and are consistent with the proposal that sexually dimorphic cues in different domains reflect a common underlying aspect of male quality. Here we present evidence for a similar correlation between men's preferences for different cues of femininity in women; although men generally preferred feminized to masculinized versions of both women's faces and voices, the strength of men's preferences for feminized versions of female faces was positively and significantly correlated with the strength of their preferences for feminized versions of women's voices. In a second study, this correlation occurred when men judged women's attractiveness as long-term, but not short-term, mates, which is consistent with previous research. Collectively, these findings (1) present novel evidence for systematic variation in men's preferences for feminine women, (2) present converging evidence for concordant preferences for sexually dimorphic traits in different domains, and (3) complement findings of correlations between women's facial and vocal femininity.

Correlated Male Preferences for Femininity in Female Faces and Voices

Sexually dimorphic physical traits are important for mate choice and mate preference in many species, including humans. Several previous studies have observed that women's preferences for physical cues of male masculinity in different domains (e.g., visual and vocal) are correlated. These correlations demonstrate systematic, rather than arbitrary, variation in women's preferences for masculine men and are consistent with the proposal that sexually dimorphic cues in different domains reflect a common underlying aspect of male quality. Here we present evidence for a similar correlation between men's preferences for different cues of femininity in women; although men generally preferred feminized to masculinized versions of both women's faces and voices, the strength of men's preferences for feminized versions of female faces was positively and significantly correlated with the strength of their preferences for feminized versions of women's voices. In a second study, this correlation occurred when men judged women's attractiveness as long-term, but not short-term, mates, which is consistent with previous research. Collectively, these findings (1) present novel evidence for systematic variation in men's preferences for feminine women, (2) present converging evidence for concordant preferences for sexually dimorphic traits in different domains, and (3) complement findings of correlations between women's facial and vocal femininity.

Women's preferences for masculinity in male faces are highest during reproductive age range and lower around puberty and post-menopause

Masculinity in male faces is thought to be a sign of mate quality and is associated with measures of long-term health. Previous studies have demonstrated that women's masculinity preferences change across the menstrual cycle with women preferring more masculine men during phases of the menstrual cycle where fertility is highest (i.e. the late follicular phase). Given the hormonal correlates of such preferences and that these hormones change across the life span, we tested for differences in female masculinity preferences at different ages. We compared the masculinity preferences of peri-pubescent girls and young adult women (Study 1), circum-menopausal women reporting to either be pre- or post-menopause (Study 2), and a large sample of women across a wide range of ages (Study 3). In all three studies, preferences for masculinity in male faces were highest in women who were at a reproductively active age. Preferences for masculinity were lower when females were peri-pubescent, post-menopausal, or at ages corresponding to these groups. These data support the notion that masculinity in male faces is an important trait for reproductively relevant mate choice decisions. These data also highlight a shift in female visual preferences for men that is associated with important stages of the lifespan. Visual preferences appear to track important hormonal changes associated with age; as women pass puberty their preferences shift towards facial traits associated with mate quality and as women undergo menopause their preferences for such facial traits decrease. Overall, these results demonstrate the important role of reproductive status and support the notion that preferences for male faces are tied to reproductively relevant hormones.

Integrating gaze direction and sexual dimorphism of face shape when perceiving the dominance of others

Although gaze direction and face shape have each been shown to affect perceptions of the dominance of others, the question whether gaze direction and face shape have independent main effects on perceptions of dominance, and whether these effects interact, has not yet been studied. To investigate this issue, we compared dominance ratings of faces with masculinised shapes and direct gaze, masculinised shapes and averted gaze, feminised shapes and direct gaze, and feminised shapes and averted gaze. While faces with direct gaze were generally rated as more dominant than those with averted gaze, this effect of gaze direction was greater when judging faces with masculinised shapes than when judging faces with feminised shapes. Additionally, faces with masculinised shapes were rated as more dominant than those with feminised shapes when faces were presented with direct gaze, but not when faces were presented with averted gaze. Collectively, these findings reveal an interaction between the effects of gaze direction and sexually dimorphic facial cues on judgments of the dominance of others, presenting novel evidence for the existence of complex integrative processes that underpin social perception of faces. Integrating information from face shape and gaze cues may increase the efficiency with which we perceive the dominance of others.

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.

Effects of ethanol and ecstasy on conditioned place preference in the rat

The club drug ecstasy (3,4-methylenedioxymethylamphetamine or MDMA) is often taken recreationally with ethanol (EtOH). We have shown previously that EtOH potentiates the psychomotor effects of MDMA in rats. More recently, we demonstrated in striatal slices that MDMA produced preferential release of serotonin, but when combined with EtOH, the preferential release shifted to dopamine, raising the possibility that administration of EtOH may increase the reward effect of MDMA. To address this possibility, adult male Long-Evans rats were tested for conditioned place preference following treatment with saline, EtOH (0.75 g/kg), MDMA (6.6 mg/kg) or the combination. The only condition that produced a preference for the compartment associated with the drug was that of the drug combination. The current data are in line with anecdotal reports and one study in humans, indicating that EtOH alters the pharmacological effects of MDMA including self reports of enhanced or prolonged euphoria. Thus, administration of EtOH might increase the risk for compulsive use of MDMA, an issue that warrants further study.

Interactions among the Effects of Head Orientation, Emotional Expression, and Physical Attractiveness on Face Preferences

Previous studies have shown that preferences for direct versus averted gaze are modulated by emotional expressions and physical attractiveness. For example, preferences for direct gaze are stronger when judging happy or physically attractive faces than when judging disgusted or physically unattractive faces. Here we show that preferences for front versus three-quarter views of faces, in which gaze direction was always congruent with head orientation, are also modulated by emotional expressions and physical attractiveness; participants demonstrated preferences for front views of faces over three-quarter views of faces when judging the attractiveness of happy, physically attractive individuals, but not when judging the attractiveness of relatively unattractive individuals or those with disgusted expressions. Moreover, further analyses indicated that these interactions did not simply reflect differential perceptions of the intensity of the emotional expressions shown in each condition. Collectively, these findings present novel evidence that the effect of the direction of the attention of others on attractiveness judgments is modulated by cues to the physical attractiveness and emotional state of the depicted individual, potentially reflecting psychological adaptations for efficient allocation of social effort. These data also present the first behavioural evidence that the effect of the direction of the attention of others on attractiveness judgments reflects viewer-referenced, rather than face-referenced, coding and/or processing of gaze direction.

Facial cues of dominance modulate the short-term gaze-cuing effect in human observers

Responding appropriately to gaze cues is essential for fluent social interaction, playing a crucial role in social learning, collaboration, threat assessment and understanding others' intentions. Previous research has shown that responses to gaze cues can be studied by investigating the gaze-cuing effect (i.e. the tendency for observers to respond more quickly to targets in locations that were cued by others' gaze than to uncued targets). A recent study demonstrating that macaques demonstrate larger gaze-cuing effects when viewing dominant conspecifics than when viewing subordinate conspecifics suggests that cues of dominance modulate the gaze-cuing effect in at least one primate species. Here, we show a similar effect of facial cues associated with dominance on gaze cuing in human observers: at short viewing times, observers demonstrated a greater cuing effect for gaze cues from masculinized (i.e. dominant) faces than from feminized (i.e. subordinate) faces. Moreover, this effect of facial masculinity on gaze cuing decreased as viewing time was increased, suggesting that the effect is driven by involuntary responses. Our findings suggest that the mechanisms that underpin reflexive gaze cuing evolved to be sensitive to facial cues of others' dominance, potentially because such differential gaze cuing promoted desirable outcomes from encounters with dominant individuals.

Sexual dimorphism of male face shape, partnership status and the temporal context of relationship sought modulate women's preferences for direct gaze

Most previous studies of face preferences have investigated the physical cues that influence face preferences. Far fewer studies have investigated the effects of cues to the direction of others' social interest (i.e. gaze direction) on face preferences. Here we found that unpartnered women demonstrated stronger preferences for direct gaze (indicating social interest) from feminine male faces than from masculine male faces when judging men's attractiveness for long-term relationships, but not when judging men's attractiveness for short-term relationships. Moreover, unpartnered women's preferences for direct gaze from feminine men were stronger for long-term than short-term relationships, but there was no comparable effect for judgements of masculine men. No such effects were evident among women with romantic partners, potentially reflecting different motivations underlying partnered and unpartnered women's judgements of men's attractiveness. Collectively these findings (1) complement previous findings whereby women demonstrated stronger preferences for feminine men as long-term than short-term partners, (2) demonstrate context-sensitivity in the integration of physical and social cues in face preferences, and (3) suggest that gaze preferences may function, at least in part, to facilitate efficient allocation of mating effort.

Circum-menopausal effects on women's judgements of facial attractiveness

The marked change in a woman's hormonal profile that happens at menopause affects many aspects of behaviour. We investigated circum-menopausal women's preferences for femininity in the faces of young adult men and women. Post-menopausal women demonstrated stronger preferences for femininity in same-sex faces than pre-menopausal women did. This effect was independent of possible effects of participant's age and suggests that dislike of feminine (i.e. attractive) same-sex competitors decreases as fertility decreases. No significant difference between pre- and post-menopausal women was observed for men's faces, potentially because circum-menopausal women do not necessarily view young adult men as potential mates. To our knowledge, this is the first study to demonstrate circum-menopausal changes in women's face preferences.

View-Contingent Aftereffects Suggest Joint Coding of Face Shape and View

While it is well established that different neural populations code different face views, behavioural evidence that these neurons also code other aspects of face shape is equivocal. For example, previous studies have interpreted the partial transfer of face aftereffects across different viewpoints as evidence for either view-specific coding of face shape or that the locus of adaptation is in face-coding mechanisms that are relatively robust to changes in face view. Here we show that it is possible to simultaneously induce aftereffects in opposite directions for 3/4 and front views of upright faces with manipulated mouth position (experiment 1). For example, simultaneous adaptation to 3/4 views with raised mouth position and front views with lowered mouth position caused raised mouth position to appear more normal for 3/4 views of novel faces, but less normal for front views. View-contingent adaptation did not occur for inverted faces, however (experiment 2). Dissociable aftereffects for different views of upright faces, but not for different views of inverted faces, suggest that neurons that code face view can also code other aspects of face shape.

Of mice and men, periodic limb movements and iron: how the human genome informs the mouse genome

The gene, BTBD9, was recently linked to restless legs syndrome, periodic limb movements and iron status in humans. In a homologous region in mouse, an area containing btbd9 was also identified as being related to iron homeostasis. This finding is important as iron status in brain has been implicated in restless legs syndrome.

Men report stronger attraction to femininity in women's faces when their testosterone levels are high

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.