MHC-assortative facial preferences in humans

Individuals tend to choose mates who are sufficiently genetically dissimilar to avoid inbreeding. As facial attractiveness is a key factor in human mate preference, we investigated whether facial preferences were related to genetic dissimilarity. We asked female volunteers to rate the attractiveness of men from photographs and compared these results with individual genotypes at the major histocompatibility complex (MHC). In contrast to previously reported preferences based on odour, we found a non-significant tendency for women to rate MHC-similar faces as more attractive, suggesting a preference for cues to a self-similar MHC in faces. Further analysis revealed that male faces received higher attractiveness scores when rated by women who were MHC-similar than by MHC-dissimilar women. Although unexpected, this MHC-similar facial preference is consistent with other studies documenting assortative preferences in humans, including for facial phenotype.     

Second to fourth digit ratio, testosterone and perceived male dominance

Previous studies have shown that male faces with extreme features associated with testosterone are perceived as dominant and masculine. Women have been reported to prefer more masculinized male faces as they may consider testosterone markers to be an 'honest' indication of good health, and such considerations may underlie their aesthetic preferences. However, pronounced testosterone facial markers are also associated with dominance, and several negative personality traits. This suggests that female aesthetic preferences may be an adaptive compromise between positive attributes associated with higher than average testosterone, and negative attributes associated with more extreme masculinization. This current study attempts to clarify the role of hormone markers in female perceptions of dominance, masculinity and attractiveness, in male facial images. Recent evidence suggests that the relative length of the 2nd to 4th finger (2D : 4D ratio) is a pointer to prenatal testosterone levels and may thus serve as a window to the prenatal hormonal environment. We measured 2D : 4D in a sample of male college students and took salivary samples to analyse circulating levels of testosterone. Women rated facial images of these males for dominance, masculinity and attractiveness. Our results show that male 2D : 4D was significantly negatively related to perceived dominance and masculinity but not attractiveness. Circulating testosterone levels were not related to dominance, masculinity or attractiveness. These findings suggest that: (i) high prenatal levels of testosterone serve to 'organize' male facial features to subsequently reflect dominance and masculine characteristics presumably activated during puberty; and (ii) attractiveness is not directly related to testosterone levels. We conclude that facial dominance and masculinity reflect a male's perceived status rather than his physical attraction to women.     

Cross-Cultural Agreement in Facial Attractiveness Preferences: The Role of Ethnicity and Gender

Previous work showed high agreement in facial attractiveness preferences within and across cultures. The aims of the current study were twofold. First, we tested cross-cultural agreement in the attractiveness judgements of White Scottish and Black South African students for own- and other-ethnicity faces. Results showed significant agreement between White Scottish and Black South African observers'' attractiveness judgements, providing further evidence of strong cross-cultural agreement in facial attractiveness preferences. Second, we tested whether cross-cultural agreement is influenced by the ethnicity and/or the gender of the target group. White Scottish and Black South African observers showed significantly higher agreement for Scottish than for African faces, presumably because both groups are familiar with White European facial features, but the Scottish group are less familiar with Black African facial features. Further work investigating this discordance in cross-cultural attractiveness preferences for African faces show that Black South African observers rely more heavily on colour cues when judging African female faces for attractiveness, while White Scottish observers rely more heavily on shape cues. Results also show higher cross-cultural agreement for female, compared to male faces, albeit not significantly higher. The findings shed new light on the factors that influence cross-cultural agreement in attractiveness preferences.     

African Perceptions of Female Attractiveness

Little is known about mate choice preferences outside Western, educated, industrialised, rich and democratic societies, even though these Western populations may be particularly unrepresentative of human populations. To our knowledge, this is the first study to test which facial cues contribute to African perceptions of African female attractiveness and also the first study to test the combined role of facial adiposity, skin colour (lightness, yellowness and redness), skin homogeneity and youthfulness in the facial attractiveness preferences of any population. Results show that youthfulness, skin colour, skin homogeneity and facial adiposity significantly and independently predict attractiveness in female African faces. Younger, thinner women with a lighter, yellower skin colour and a more homogenous skin tone are considered more attractive. These findings provide a more global perspective on human mate choice and point to a universal role for these four facial cues in female facial attractiveness.     

Facial attractiveness judgements reflect learning of parental age characteristics

Mate preferences are shaped by infant experience of parental characteristics in a wide variety of species. Similar processes in humans may lead to physical similarity between parents and mates, yet this possibility has received little attention. The age of parents is one salient physical characteristic that offspring may attend to. The current study used computer-graphic faces to examine how preferences for age in faces were influenced by parental age. We found that women born to 'old' parents (over 30) were less impressed by youth, and more attracted to age cues in male faces than women with 'young' parents (under 30). For men, preferences for female faces were influenced by their mother's age and not their father's age, but only for long-term relationships. These data indicate that judgements of facial attractiveness in humans reflect the learning of parental characteristics.     

African and European perception of African female attractiveness

Majority of research on attractiveness is restricted to faces of European origin. The perception of attractiveness may, however, vary across communities due to variations in both facial morphology and local standards of beauty. We investigated the relative contribution of four facial markers of attractiveness based on 101 female facial portraits (standardized, non-manipulated) from Cameroon and Namibia, which were assessed by local male raters and by raters from a distant European population, the Czech Republic. Images from Cameroon include only women of Bantu origin, while Namibians are represented by women of both Bantu (Owambo/Herero) and Nama origin. While controlling for age and BMI, we explored the relationship between female attractiveness and a set of facial traits: fluctuating asymmetry, averageness, shape sexual dimorphism, and skin color (rated and measured in CIELab color space).In the Cameroonian sample, local male raters favored lighter-skinned female faces with morphology closer to average. The attractiveness of Nama women as rated by Nama men positively correlated with lighter complexion, but this did not extend to rating by Cameroonian men. The attractiveness of Namibian Owambo/Herero women was positively associated with facial femininity and lighter complexion when judged by both Cameroonian and Nama male raters. In all samples, the attractiveness as rated by Czech men was predicted by age and BMI, but not by skin color. We found no significant association between attractiveness and fluctuating asymmetry in any of the tested samples. When controlling for age, the effect of skin color on attractiveness turned to be non-significant in the Owambo/Herrero and Nama sample, but remained significant in the Cameroonian sample. Variations in skin color thus represent an important factor of African female attractiveness within the African context, but they do not seem to affect judgements made by European raters. Sensitivity to some facial markers of female attractiveness thus seems to be restricted to regional populations and/or constrained by shared ethnicity.     

Facial movement varies by sex and is related to attractiveness

Facial movement has received little attention in studies of human attractiveness, yet dynamic displays are an important aspect of courtship in many species. This experiment investigated whether facial movement could be used to identify sex, and whether the ease of identification was associated with attractiveness. We removed shape cues to sex by applying movement from individual faces to a standardised facial model. Participants were able to distinguish between male and female animations of this model at levels above chance. Furthermore, there was a positive association between ease of sex identification and attractiveness for female, but not male, faces. Analysis of facial movement suggested several behaviours that are more frequent in women than men (blinking, tilting, nodding, shaking, and amount of movement). Although some of these behaviours may be cues to sex identification, none alone was directly linked to attractiveness. Our findings suggest that feminine motion is attractive in female faces, but sexually recognisable movement has no clear influence on male attractiveness, in agreement with work on static faces employing composite images.     

Populational differences in attractiveness judgements of male and female faces: Comparing British and Jamaican samples

In the UK and Japan, both men and women prefer somewhat feminised opposite-sex faces, especially when choosing a long-term partner. Such faces are perceived as more honest, caring, and sensitive; traits that may be associated with successful male parental investment. By contrast, women prefer less feminised faces for short-term relationships and when they are near ovulation. As genetic quality may be associated with facial masculinity, women may ‘trade-off’ cues between genetic quality and paternal investment in potential partners. No analogous trade-off has been suggested to influence men's preferences, as both attributions of prosociality and potential cues to biological quality are associated with facial femininity in female faces. Ecological and cultural factors may influence the balance of trade-offs leading to populational differences in preferences. We predicted that Jamaican women would prefer more masculine faces than British women do because parasite load is higher in Jamaica, medical care less common (historically and currently), and male parental investment less pronounced. Male preferences, however, were predicted to vary less cross-culturally, as no trade-off has been identified in female facial characteristics. We constructed masculinised and feminised digital male and female face stimuli of three populations (Jamaican, Japanese, and British) and presented them to men and women in Jamaica and in Britain. The results demonstrated that Jamaican women preferred more masculine male faces than their British counterparts did. Jamaican men tended to prefer more masculine female faces than did British men did, but this effect was complicated by an interaction suggesting that more feminised faces were preferred within culture.     

Genetic diversity revealed in human faces

From an evolutionary perspective, human facial attractiveness is proposed to signal mate quality. Using a novel approach to the study of the genetic basis of human preferences for facial features, we investigated whether attractiveness signals mate quality in terms of genetic diversity. Genetic diversity in general has been linked to fitness and reproductive success, and genetic diversity within the major histocompatibility complex (MHC) has been linked to immunocompetence and mate preferences. We asked whether any preference for genetic diversity is specific to MHC diversity or reflects a more general preference for overall genetic diversity. We photographed and genotyped 160 participants using microsatellite markers situated within and outside the MHC, and calculated two measures of genetic diversity: mean heterozygosity and standardized mean d(2). Our results suggest a special role for the MHC in female preferences for male faces. MHC heterozygosity positively predicted male attractiveness, and specifically facial averageness, with averageness mediating the MHC-attractiveness relationship. For females, standardized mean d(2) at non-MHC loci predicted facial symmetry. Thus, attractive facial characteristics appear to provide visual cues to genetic quality in both males and females, supporting the view that face preferences have been shaped by selection pressures to identify high-quality mates.     

Female Preferences for Male Vocal and Facial Masculinity in Videos

Vocal and facial masculinity are cues to underlying testosterone in men and influence women’s mate preferences. Consistent with the proposal that facial and vocal masculinity signal common information about men, prior work has revealed correlated female preferences for male facial and vocal masculinity. Previous studies have assessed women’s preferences for male facial and vocal masculinity by presenting faces and voices independently and using static face stimuli. By contrast, here we presented women with short video clips in which male faces and voices were simultaneously manipulated in masculinity. We found that women who preferred masculine faces also preferred masculine voices. Furthermore, women whose faces were rated as relatively more attractive preferred both facial and vocal masculinity more than did women whose faces were rated as less attractive. These findings complement other evidence for cross‐modal masculinity preferences among women and demonstrate that preferences observed in studies using still images and/or independently presented vocal stimuli are also observed when dynamic faces and voices are displayed simultaneously in video format.     

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.     

Facial correlates of sociosexuality

Previous studies have documented variation in sexual behaviour between individuals leading to the notion of ‘restricted’ individuals (i.e., people who prefer long-term relationships) and ‘unrestricted’ individuals (i.e., people who are open to short-term relationships). This distinction is often referred to as sociosexual orientation. Observers have been previously found to distinguish sociosexuality from video footage of individuals, although the specific cues used have not been identified. Here we assessed the ability of observers to judge sexual strategy based specifically on cues in both facial composites and real faces. We also assessed how observers' perceptions of the masculinity/femininity and attractiveness of faces relate to the sociosexual orientation of the pictured individuals. Observers were generally able to identify restricted vs. unrestricted individuals from cues in both composites and real faces. Unrestricted sociosexuality was generally associated with greater attractiveness in female composites and real female faces and greater masculinity in male composites. Although male observers did not generally associate sociosexuality with male attractiveness, female observers generally preferred more restricted males' faces (i.e., those with relatively strong preferences for long-term relationships). Collectively, our results support previous findings that androgenisation in men is related to less restricted sexual behaviour and suggest that women are averse to unrestricted men.     

Preferences for symmetry in human faces in two cultures: data from the UK and the Hadza, an isolated group of hunter-gatherers

Many studies show agreement within and between cultures for general judgements of facial attractiveness. Few studies, however, have examined the attractiveness of specific traits and few have examined preferences in hunter-gatherers. The current study examined preferences for symmetry in both the UK and the Hadza, a hunter-gatherer society of Tanzania. We found that symmetry was more attractive than asymmetry across both the cultures and was more strongly preferred by the Hadza than in the UK. The different ecological conditions may play a role in generating this difference. Such variation in preference may be adaptive if it reflects adaptation to local conditions. Symmetry is thought to indicate genetic quality, which may be more important among the Hadza with much higher mortality rates from birth onwards. Hadza men who were more often named as good hunters placed a greater value on symmetry in female faces. These results suggest that high quality Hadza men are more discriminating in their choice of faces. Hadza women had increased preferences for symmetry in men's faces when they were pregnant or nursing, perhaps due to their increased discrimination and sensitivity to foods and disease harmful to a foetus or nursing infant. These results imply that symmetry is an evolutionarily relevant trait and that variation in symmetry preference appears strategic both between cultures and within individuals of a single culture.     

Face perception is modulated by sexual preference

Face perception is mediated by a distributed neural system in the human brain . The response to faces is modulated by cognitive factors such as attention, visual imagery, and emotion ; however, the effects of gender and sexual orientation are currently unknown. We used fMRI to test whether subjects would respond more to their sexually preferred faces and predicted such modulation in the reward circuitry. Forty heterosexual and homosexual men and women viewed photographs of male and female faces and assessed facial attractiveness. Regardless of their gender and sexual orientation, all subjects similarly rated the attractiveness of both male and female faces. Within multiple, bilateral face-selective regions in the visual cortex, limbic system, and prefrontal cortex, similar patterns of activation were found in all subjects in response to both male and female faces. Consistent with our hypothesis, we found a significant interaction between stimulus gender and the sexual preference of the subject in the thalamus and medial orbitofrontal cortex, where heterosexual men and homosexual women responded more to female faces and heterosexual women and homosexual men responded more to male faces. Our findings suggest that sexual preference modulates face-evoked activation in the reward circuitry.     

Body Shape Preferences: Associations with Rater Body Shape and Sociosexuality

There is accumulating evidence of condition-dependent mate choice in many species, that is, individual preferences varying in strength according to the condition of the chooser. In humans, for example, people with more attractive faces/bodies, and who are higher in sociosexuality, exhibit stronger preferences for attractive traits in opposite-sex faces/bodies. However, previous studies have tended to use only relatively simple, isolated measures of rater attractiveness. Here we use 3D body scanning technology to examine associations between strength of rater preferences for attractive traits in opposite-sex bodies, and raters’ body shape, self-perceived attractiveness, and sociosexuality. For 118 raters and 80 stimuli models, we used a 3D scanner to extract body measurements associated with attractiveness (male waist-chest ratio [WCR], female waist-hip ratio [WHR], and volume-height index [VHI] in both sexes) and also measured rater self-perceived attractiveness and sociosexuality. As expected, WHR and VHI were important predictors of female body attractiveness, while WCR and VHI were important predictors of male body attractiveness. Results indicated that male rater sociosexuality scores were positively associated with strength of preference for attractive (low) VHI and attractive (low) WHR in female bodies. Moreover, male rater self-perceived attractiveness was positively associated with strength of preference for low VHI in female bodies. The only evidence of condition-dependent preferences in females was a positive association between attractive VHI in female raters and preferences for attractive (low) WCR in male bodies. No other significant associations were observed in either sex between aspects of rater body shape and strength of preferences for attractive opposite-sex body traits. These results suggest that among male raters, rater self-perceived attractiveness and sociosexuality are important predictors of preference strength for attractive opposite-sex body shapes, and that rater body traits –with the exception of VHI in female raters– may not be good predictors of these preferences in either sex.     

Exposure to visual cues of pathogen contagion changes preferences for masculinity and symmetry in opposite-sex faces

Evolutionary approaches to human attractiveness have documented several traits that are proposed to be attractive across individuals and cultures, although both cross-individual and cross-cultural variations are also often found. Previous studies show that parasite prevalence and mortality/health are related to cultural variation in preferences for attractive traits. Visual experience of pathogen cues may mediate such variable preferences. Here we showed individuals slideshows of images with cues to low and high pathogen prevalence and measured their visual preferences for face traits. We found that both men and women moderated their preferences for facial masculinity and symmetry according to recent experience of visual cues to environmental pathogens. Change in preferences was seen mainly for opposite-sex faces, with women preferring more masculine and more symmetric male faces and men preferring more feminine and more symmetric female faces after exposure to pathogen cues than when not exposed to such cues. Cues to environmental pathogens had no significant effects on preferences for same-sex faces. These data complement studies of cross-cultural differences in preferences by suggesting a mechanism for variation in mate preferences. Similar visual experience could lead to within-cultural agreement and differing visual experience could lead to cross-cultural variation. Overall, our data demonstrate that preferences can be strategically flexible according to recent visual experience with pathogen cues. Given that cues to pathogens may signal an increase in contagion/mortality risk, it may be adaptive to shift visual preferences in favour of proposed good-gene markers in environments where such cues are more evident.     

Attractiveness of men's faces in relation to women's phase of menstrual cycle

In between-subjects studies on two groups of women of the same age, we show that women assess male's facial attractiveness differently in the follicular (F) and luteal (L) phases. In the high conception risk phase (F), women tended to give higher scores to male faces than when they were in the luteal phase. During the five first days of the cycle, i.e. when the estrogen level is still low, women assessed men's facial attractiveness relatively highly. We suggest that it is progesterone in the luteal phase that is responsible for lower attractiveness assigned then to male faces. We also tested which anthropometric facial traits or indices influence male attractiveness. We found that assessments of attractiveness were correlated only with mouth height (positively) and the angle between the middle of the mouth and the middle of the eyes (negatively). The results are compared with those from other studies and discussed in the light of evolutionary biology.     

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.     

Men's Preferences for Women's Femininity in Dynamic Cross-Modal Stimuli

Men generally prefer feminine women''s faces and voices over masculine women''s faces and voices, and these cross-modal preferences are positively correlated. Men''s preferences for female facial and vocal femininity have typically been investigated independently by presenting soundless still images separately from audio-only vocal recordings. For the first time ever, we presented men with short video clips in which dynamic faces and voices were simultaneously manipulated in femininity/masculinity. Men preferred feminine men''s faces over masculine men''s faces, and preferred masculine men''s voices over feminine men''s voices. We found that men preferred feminine women''s faces and voices over masculine women''s faces and voices. Men''s attractiveness ratings of both feminine and masculine faces were increased by the addition of vocal femininity. Also, men''s attractiveness ratings of feminine and masculine voices were increased by the addition of facial femininity present in the video. Men''s preferences for vocal and facial femininity were significantly and positively correlated when stimuli were female, but not when they were male. Our findings complement other evidence for cross-modal femininity preferences among male raters, and show that preferences observed in studies using still images and/or independently presented vocal stimuli are also observed when dynamic faces and voices are displayed simultaneously in video format.     

Face and voice attractiveness judgments change during adolescence

Attractiveness judgments are thought to underpin adaptive mate choice decisions. We investigated how these judgments change during adolescence when mate choice is becoming relevant. Adolescents aged 11–15 evaluated faces and voices manipulated along dimensions that affect adults' judgments of attractiveness and that are thought to cue mate value. Facial stimuli consisted of pairs of faces that were more or less average, more or less feminine, or more or less symmetric. The adolescents selected the more average, symmetric, and feminine faces as more attractive more often than chance, but judgments of some facial traits differed significantly with rater age and sex, indicating a role of development in judgments of facial cues. Vocal stimuli consisted of pairs of voices manipulated to raise or lower perceived pitch. The older but not younger girls selected the lower-pitched male voices as more attractive at rates above chance, while the younger but not older boys selected the higher-pitched female voices as more attractive. Controlling for rater age, increased pubertal development was associated with increased selection of lower-pitched boys' voices by girls and decreased selection of feminized male faces by boys. Our results are the first to demonstrate that adolescents show somewhat similar attractiveness judgments to adults in age-matched stimuli and that age, sex, and pubertal development have measurable effects on adolescents' attractiveness judgments. They suggest that attractiveness judgments in humans, at least for some traits, are facultatively calibrated to the individual's life stage, only reaching adult values upon sexual maturity when mate choice decisions become relevant.