A new viewpoint on the evolution of sexually dimorphic human faces

Human faces show marked sexual shape dimorphism, and this affects their attractiveness. Humans also show marked height dimorphism, which means that men typically view women's faces from slightly above and women typically view men's faces from slightly below. We tested the idea that this perspective difference may be the evolutionary origin of the face shape dimorphism by having males and females rate the masculinity/femininity and attractiveness of male and female faces that had been manipulated in pitch (forward or backward tilt), simulating viewing the face from slightly above or below. As predicted, tilting female faces upwards decreased their perceived femininity and attractiveness, whereas tilting them downwards increased their perceived femininity and attractiveness. Male faces tilted up were judged to be more masculine, and tilted down judged to be less masculine. This suggests that sexual selection may have embodied this viewpoint difference into the actual facial proportions of men and women.     

男性化与女性化对面孔偏好的影响—— 基于图像处理技术和眼动的检验

采用图像处理技术和眼动探讨了性别二态线索对面孔偏好的影响。实验1发现非面孔线索未掩蔽和掩蔽时, 感知男性化技术与原始照片条件下女性化的男性面孔更有吸引力和信任度; 性别二态技术条件下, 非面孔线索未掩蔽时男性化的男性面孔更有吸引力和信任度。实验2表明被试对男性面孔的平均瞳孔大小和注视次数均大于和多于女性面孔, 首次注视时间短于女性面孔; 被试对男性化面孔的首次注视时间和首次注视持续时间均长于女性化面孔。     

The role of facial attractiveness and facial masculinity/femininity in sex classification of faces

We tested whether adults (experiment 1) and 4 - 5-year-old children (experiment 2) identify the sex of highly attractive faces faster and more accurately than not very attractive faces in a reaction-time task. We also assessed whether facial masculinity/femininity facilitated identification of sex. Results showed that attractiveness facilitated adults' sex classification of both female and male faces and children's sex classification of female, but not male, faces. Moreover, attractiveness affected the speed and accuracy of sex classification independently of masculinity/femininity. High masculinity in male faces, but not high femininity in female faces, also facilitated sex classification for both adults and children. These findings provide important new data on how the facial cues of attractiveness and masculinity/femininity contribute to the task of sex classification and provide evidence for developmental differences in how adults and children use these cues. Additionally, these findings provide support for Langlois and Roggman's (1990 Psychological Science 1 115 121) averageness theory of attractiveness.     

The role of symmetry in attraction to average faces

Although many studies have demonstrated that average faces tend to be attractive, few studies have examined the extent to which symmetry contributes to the attractiveness of average faces. Such studies are potentially important, however, because average faces are highly symmetric and increasing the symmetry of face images increases their attractiveness. Here we demonstrate that increasing averageness of 2-D face shape independently of symmetry is sufficient to increase attractiveness, indicating that preferences for symmetry cannot solely explain the attractiveness of average faces. Additionally, we show that averageness preferences are significantly weaker when the effects of symmetry are controlled for using computer graphic methods than when the effects of symmetry are not controlled for, suggesting that symmetry contributes to the attractiveness of average faces. Importantly, this latter finding was not explained by the greater perceived similarity between versions offaces that varied in averageness, but not symmetry, than between versions of faces that varied in both averageness and symmetry.     

A statistical model of facial attractiveness

Previous research has identified facial averageness and sexual dimorphism as important factors in facial attractiveness. The averageness and sexual dimorphism accounts provide important first steps in understanding what makes faces attractive, and should be valued for their parsimony. However, we show that they explain relatively little of the variance in facial attractiveness, particularly for male faces. As an alternative to these accounts, we built a regression model that defines attractiveness as a function of a face's position in a multidimensional face space. The model provides much more predictive power than the averageness and sexual dimorphism accounts and reveals previously unreported components of attractiveness. The model shows that averageness is attractive in some dimensions but not in others and resolves previous contradictory reports about the effects of sexual dimorphism on the attractiveness of male faces.     

Adolescents’ preferences for sexual dimorphism are influenced by relative exposure to male and female faces

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.     

Adolescents’ preferences for sexual dimorphism are influenced by relative exposure to male and female faces

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.     

Age,puberty and attractiveness judgments in adolescents

Previous work has suggested that judgments of the attractiveness of some facial and vocal features change during adolescence. Here, over 70 Czech adolescents aged 12–14 made forced-choice attractiveness judgments on adolescent faces manipulated in symmetry, averageness and femininity, and on adolescent opposite-sex voices manipulated in fundamental frequency (perceived as pitch), and completed questionnaires on pubertal development. Consistent with typical adult judgments, adolescents selected the symmetric, average and feminine male and female faces as more attractive significantly more often than the asymmetric, non-average and masculine faces respectively. Moreover, preferences for symmetric faces were positively associated with adolescents’ age and stage of pubertal development. Unexpectedly, voice pitch did not significantly influence adolescents’ attractiveness judgments. Collectively, these findings present new evidence using refined methodology that adolescent development is related to variation in attractiveness judgments.     

Extraversion predicts individual differences in women’s face preferences

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.     

性别二态线索对男性面孔吸引力影响的方法差异之争

性别二态线索(男性化-女性化线索)对男性面孔吸引力的影响一直存在不一致的结果,研究者主要从方法差异对此不一致性进行解释.本文首先对操作男性化面孔刺激的不同计算机图像处理技术进行了阐述,主要包括性别二态技术、感知男性化技术和青春期发展技术,并进一步梳理了以往采用不同技术进行比较的相关研究,最后对未来研究提出了展望.     

Attractiveness of facial averageness and symmetry in non-western cultures: in search of biologically based standards of beauty.

Averageness and symmetry are attractive in Western faces and are good candidates for biologically based standards of beauty. A hallmark of such standards is that they are shared across cultures. We examined whether facial averageness and symmetry are attractive in non-Western cultures. Increasing the averageness of individual faces, by warping those faces towards an averaged composite of the same race and sex, increased the attractiveness of both Chinese (experiment 1) and Japanese (experiment 2) faces, for Chinese and Japanese participants, respectively. Decreasing averageness by moving the faces away from an average shape decreased attractiveness. We also manipulated the symmetry of Japanese faces by blending each original face with its mirror image to create perfectly symmetric versions. Japanese raters preferred the perfectly symmetric versions to the original faces (experiment 2). These findings show that preferences for facial averageness and symmetry are not restricted to Western cultures, consistent with the view that they are biologically based. Interestingly, it made little difference whether averageness was manipulated by using own-race or other-race averaged composites and there was no preference for own-race averaged composites over other-race or mixed-race composites (experiment 1). We discuss the implications of these results for understanding what makes average faces attractive. We also discuss some limitations of our studies, and consider other lines of converging evidence that may help determine whether preferences for average and symmetric faces are biologically based.     

Extraversion predicts individual differences in women’s face preferences

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.     

Dissociating averageness and attractiveness: attractive faces are not always average

Although the averageness hypothesis of facial attractiveness proposes that the attractiveness of faces is mostly a consequence of their averageness, 1 study has shown that caricaturing highly attractive faces makes them mathematically less average but more attractive. Here the authors systematically test the averageness hypothesis in 5 experiments using both rating and visual adaptation paradigms. Visual adaptation has previously been shown to increase both preferences for previously viewed face types (i.e., attractiveness) and their perceived normality (i.e., averageness). The authors used a visual adaptation procedure to test whether facial attractiveness is dependent upon faces' proximity to average (averageness hypothesis) or their location relative to average along an attractiveness dimension in face space (contrast hypothesis). While the typical pattern of change due to visual adaptation was found for judgments of normality, judgments of attractiveness resulted in a very different pattern. The results of these 5 experiments conclusively support the proposal that there are specific nonaverage characteristics that are particularly attractive. The authors discuss important implications for the interpretation of studies using a visual adaptation paradigm to investigate attractiveness.     

Female condition influences preferences for sexual dimorphism in faces of male humans (Homo sapiens)

In some species, female condition correlates positively with preferences for male secondary sexual traits. Women's preferences for sexually dimorphic characteristics in male faces (facial masculinity) have recently been reported to covary with self-reported attractiveness. As women's attractiveness has been proposed to signal reproductive condition, the findings in human (Homo sapiens) and other species may reflect similar processes. The current study investigated whether the covariation between condition and preferences for masculinity would generalize to 2 further measures of female attractiveness: other-rated facial attractiveness and waist-to-hip ratio (WHR). Women with high (unattractive) WHR and/or relatively low other-rated facial attractiveness preferred more "feminine" male faces when choosing faces for a long-term relationship than when choosing for a short-term relationship, possibly reflecting diverse tactics in female mate choice.     

Lip colour affects perceived sex typicality and attractiveness of human faces

The luminance contrast between facial features and facial skin is greater in women than in men, and women's use of make-up enhances this contrast. In black-and-white photographs, increased luminance contrast enhances femininity and attractiveness in women's faces, but reduces masculinity and attractiveness in men's faces. In Caucasians, much of the contrast between the lips and facial skin is in redness. Red lips have been considered attractive in women in geographically and temporally diverse cultures, possibly because they mimic vasodilation associated with sexual arousal. Here, we investigate the effects of lip luminance and colour contrast on the attractiveness and sex typicality (masculinity/femininity) of human faces. In a Caucasian sample, we allowed participants to manipulate the colour of the lips in colour-calibrated face photographs along CIELab L* (light--dark), a* (red--green), and b* (yellow--blue) axes to enhance apparent attractiveness and sex typicality. Participants increased redness contrast to enhance femininity and attractiveness of female faces, but reduced redness contrast to enhance masculinity of men's faces. Lip blueness was reduced more in female than male faces. Increased lightness contrast enhanced the attractiveness of both sexes, and had little effect on perceptions of sex typicality. The association between lip colour contrast and attractiveness in women's faces may be attributable to its association with oxygenated blood perfusion indicating oestrogen levels, sexual arousal, and cardiac and respiratory health.     

The processing of spatial information in short-term memory: Insights from eye tracking the path length effect

Effects of averageness and symmetry on the judgment of facial attractiveness were investigated using a generalized Procrustes method and multiple regression analyses. Participants (n = 114) rated attractiveness of 96 photographs of faces with neutral expressions. Through a generalized Procrustes method, the faces and their mirror-reversed versions were represented as points on a hyperplane. Both averageness and symmetry of each individual were defined as distances on the plane. A multiple regression analysis was performed to examine the effect of symmetry and averageness for each gender. For male faces, both symmetry and averageness affected attractiveness ratings positively , and there was no difference between the effects of averageness and symmetry. On the other hand, for female faces only averageness affected attractiveness, whereas symmetry did not. However, these effects were not large.     

Why are average faces attractive? The effect of view and averageness on the attractiveness of female faces

Images of faces manipulated to make their shapes closer to the average are perceived as more attractive. The influences of symmetry and averageness are often confounded in studies based on full-face views of faces. Two experiments are reported that compared the effect of manipulating the averageness of female faces in profile and full-face views. Use of a profile view allows a face to be ”morphed“ toward an average shape without creating an image that becomes more symmetrical. Faces morphed toward the average were perceived as more attractive in both views, but the effect was significantly stronger for full-face views. Both full-face and profile views morphed away from the average shape were perceived as less attractive. It is concluded that the effect of averageness is independent of any effect of symmetry on the perceived attractiveness of female faces.     

Sexual dimorphism and attractiveness in Asian and White faces

Marriages between White men and Asian women are over twice as frequent as those between White women and Asian men. Recent research has proposed that this imbalance may be explained by the finding that, on average, White men are perceived as more attractive than Asian men, and Asian women are perceived as more attractive than White women, possibly because Asian faces are perceived as more feminine than White faces. Here, we explore whether Asian faces are perceived as more feminine than White faces. Thirty-five Malaysian Chinese (20 male) and 30 Australian White (12 male) participants manipulated 100 face photographs (50 Asian; 50 White; half male) on a masculinity/femininity axis to optimize attractive appearance. As predicted, White women’s faces were increased more in femininity than Asian women’s faces, and White men’s faces were feminized more than Asian men’s faces to optimize attractiveness. These findings suggest that White faces are perceived as more masculine than Asian faces.     

The role of femininity and averageness of voice pitch in aesthetic judgments of women's voices

Although averageness is preferred in auditory stimuli (eg music) and non-face objects (eg wristwatches), exaggerated feminine characteristics are preferred to averageness in female faces. To establish whether or not men prefer femininity in female voices to average characteristics, we conducted a correlational study (study 1) to assess the relationship between voice pitch and attractiveness ratings. We found a positive linear relationship between voice pitch and attractiveness ratings. In study 2 we manipulated pitch in women's voices with low (lower than average), average, and high (higher than average) starting pitches and gauged men's preferences. Men preferred women's voices with raised pitch for all levels of starting pitch. These findings suggest that men prefer high voice pitch to average voice pitch in women's voices.     

Infant's visual preferences for facial traits associated with adult attractiveness judgements: Data from eye-tracking

Human preferences for facial attractiveness appear to emerge at an early stage during infant development. A number of studies have demonstrated that infants display a robust preference for facial attractiveness, preferring to look at physically attractive faces versus less attractive faces as judged by adults. However, to-date, relatively little is known about which traits of the face infants use to base these preferences upon. In contrast, a large number of studies conducted with human adults have identified that preference for attractive faces can be attributed to a number of specific facial traits. The purpose of the experiments here was to measure and assess infant's visual preference via eye-tracker technology for faces manipulated for one of three traits known to effect attractiveness judgments in adult preference tests: symmetry, averageness, and sexually dimorphic traits. Sixty-four infants (28 female and 36 male) aged between 12 and 24 months old each completed a visual paired comparison (VPC) task for one of the three facial dimensions investigated. Data indicated that infants displayed a significant visual preference for facial symmetry analogous to those preferences displayed by adults. Infants also displayed a significant visual preference for feminine versions of faces, in line with some studies of adult preferences. Visual preferences for facial non-averageness, or distinctiveness were also seen, a pattern opposite to that seen in adults. These findings demonstrate that infant's appreciation for facial attractiveness in adult images between the ages of 12 and 24 months of age is based on some, but not all, traits that adults find attractive.