Preferences for sexual dimorphism on attractiveness levels: An eye-tracking study

Previous studies on sexual dimorphism showed feminine preferences in female faces and mixed findings in male faces by choosing which is more attractive in a pair of a masculine face and a feminine face. However, very little is known about how people make fine-grained visual assessments of such images and the attractiveness levels of faces are not received much attention. Recently a large number of androgynous stars appear in the media, which triggers a hot phenomenon of imitating them. Here we examine the influence of androgynous stars on people’s facial preferences for sexual dimorphism in male and female faces on different attractiveness levels using eye-tracking techniques. In male faces we found both male and female participants preferred masculine faces to androgynous faces in high attractiveness, but mixed results in low attractiveness. In female faces we found both male and female participants preferred feminine faces to androgynous faces in high attractiveness, but no preferences in low attractiveness. Results suggest that attractiveness levels of faces might be a factor causing inconsistency in sexual dimorphism preference for male faces and that androgynous faces are not preferred, which reveals that androgynous phenomenon might not be caused by facial attractiveness.     

Evolutionary Psychology of Facial Attractiveness

The human face communicates an impressive number of visual signals. Although adults' ratings of facial attractiveness are consistent across studies, even cross-culturally, there has been considerable controversy surrounding attempts to identify the facial features that cause faces to be judged attractive or unattractive. Studies of physical attractiveness have attempted to identify the features that contribute to attractiveness by studying the relationships between attractiveness and (a) symmetry, (b) averageness, and (c) nonaverage sexually dimorphic features (hormone markers). Evolutionary psychology proposes that these characteristics all pertain to health, suggesting that humans have evolved to view certain features as attractive because they were displayed by healthy individuals. However, the question remains how single features that are considered attractive relate to each other, and if they form a single ornament that signals mate quality. Moreover, some researchers have recently explained attractiveness preferences in terms of individual differences that are predictable. This article briefly describes what is currently known from attractiveness research, reviews some recent advances, and suggests areas for future researchers' attention.     

Are average and symmetric faces attractive to infants? Discrimination and looking preferences

Young infants prefer to look at faces that adults find attractive, suggesting a biological basis for some face preferences. However, the basis for infant preferences is not known. Adults find average and symmetric faces attractive. We examined whether 5-8-month-old infants discriminate between different levels of averageness and symmetry in faces, and whether they prefer to look at faces with higher levels of these traits. Each infant saw 24 pairs of female faces. Each pair consisted of two versions of the same face differing either in averageness (12 pairs) or symmetry (12 pairs). Data from the mothers confirmed that adults preferred the more average and more symmetric versions in each pair. The infants were sensitive to differences in both averageness and symmetry, but showed no looking preference for the more average or more symmetric versions. On the contrary, longest looks were significantly longer for the less average versions, and both longest looks and first looks were marginally longer for the less symmetric versions. Mean looking times were also longer for the less average and less symmetric versions, but those differences were not significant. We suggest that the infant looking behaviour may reflect a novelty preference rather than an aesthetic preference.     

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.     

The role of facial orientation in newborn infants’ preference for attractive faces

Several previous experiments have found that newborn and young infants will spend more time looking at attractive faces when these are shown paired with faces judged by adults to be unattractive. Two experimental conditions are described whose aim was to find whether the ‘attractiveness effect’ is affected by the orientation of the facial stimuli. Pairs of attractive and less attractive faces (as judged by adults) were shown to newborn infants (mean age 2 days 20.5 hours), where each pair was presented both upright and inverted through 180°. In the former (upright) condition, but not the latter (inverted) condition, the infants looked longer at the attractive faces, and the difference in attractiveness preference between the conditions was statistically significant. These findings are clear evidence that infants’ early representation of faces contains information about faces that is orientation‐specific. The results are discussed in terms of innate facial representations and rapid learning about faces in the hours from birth.     

Have you got the look? Gaze direction affects judgements of facial attractiveness

Much is known about the attractiveness of physical attributes, such as symmetry and averageness. Here we examine the effect of a social cue, eye-gaze direction, on facial attractiveness. Given that direct gaze signals social engagement, we predicted that faces showing direct gaze would be preferred to faces showing averted gaze. Thirty-two males completed two tasks designed to assess preferences for female faces displaying a neutral expression. Participants were more likely to select the face with direct gaze, when choosing the more attractive face from direct- and averted-gaze versions of the same face. This direct-gaze preference was stronger for high-attractive than low-attractive face sets, but was present for both. Attractiveness ratings were also higher for faces with direct than averted gaze. Interestingly, stimulus inversion weakened the preference for inverted faces, which suggests the preference does not simply reflect a bilateral symmetry bias.     

Facial symmetry and the perception of beauty

Evolutionary, as well as cultural, pressures may contribute to our perceptions of facial attractiveness. Biologists predict that facial symmetry should be attractive, because it may signal mate quality. We tested the prediction that facial symmetry is attractive by manipulating the symmetry of individual faces and observing the effect on attractiveness, and by examining whether natural variations in symmetry (between faces) correlated with perceived attractiveness. Attractiveness increased when we increased symmetry, and decreased when we reduced symmetry, in individual faces (Experiment 1), and natural variations in symmetry correlated significantly with attractiveness (Experiments 1 and 1A). Perfectly symmetric versions, made by blending the normal and mirror images of each face, were preferred to less symmetric versions of the same faces (even when those versions were also blends) (Experiments 1 and 2). Similar results were found when subjects judged the faces on appeal as a potential life partner, suggesting that facial symmetry may affect human mate choice. We conclude that facial symmetry is attractive and discuss the possibility that this preference for symmetry may be biologically based.     

Heterosexual romantic couples mate assortatively for facial symmetry, but not masculinity

Preferences for partners with symmetric and sex-typical faces are well documented and considered evidence for the good-genes theory of mate choice. However, it is unclear whether preferences for these traits drive the real-world selection of mates. In two samples of young heterosexual couples from the United Kingdom (Study 1) and the United States (Study 2), the authors found assortment for facial symmetry but not for sex typicality or independently rated attractiveness. Within-couple similarity in these traits did not predict relationship duration or quality, although female attractiveness and relationship duration were negatively correlated among couples in which the woman was the more attractive partner. The authors conclude that humans may mate assortatively on facial symmetry, but this remains just one of the many physical and nonphysical traits to which people likely attend when forming romantic partnerships. This is also the first evidence that preferences for symmetry transfer from the laboratory to a real-world setting.     

Origins of a stereotype: categorization of facial attractiveness by 6-month-old infants

Like adults, young infants prefer attractive to unattractive faces (e.g. Langlois, Roggman, Casey, Ritter, Rieser‐Danner & Jenkins, 1987 ; Slater, von der Schulenburg, Brown, Badenoch, Butterworth, Parsons & Samuels, 1998 ). Older children and adults stereotype based on facial attractiveness ( Eagly, Ashmore, Makhijani & Longo, 1991 ; Langlois, Kalakanis, Rubenstein, Larson, Hallam & Smooth, 2000 ). How do preferences for attractive faces develop into stereotypes? Several theories of stereotyping posit that categorization of groups is necessary before positive and negative traits can become linked to the groups (e.g. Tajfel, Billig, Bundy & Flament, 1971 ; Zebrowitz‐McArthur, 1982 ). We investigated whether or not 6‐month‐old infants can categorize faces as attractive or unattractive. In Experiment 1, we familiarized infants to unattractive female faces; in Experiment 2, we familiarized infants to attractive female faces and tested both groups of infants on novel faces from the familiar or novel attractiveness category. Results showed that 6‐month‐olds categorized attractive and unattractive female faces into two different groups of faces. Experiments 3 and 4 confirmed that infants could discriminate among the faces used in Experiments 1 and 2, and therefore categorized the faces based on their similarities in attractiveness rather than because they could not differentiate among the faces. These findings suggest that categorization of facial attractiveness may underlie the development of the ‘beauty is good’ stereotype.     

Effects of the beholder's age on the perception of facial attractiveness

Children have been shown to prefer faces rated as highly attractive by adults over faces rated as quite unattractive. We investigated to what extent this agreement holds not only for the general direction of preferences but for preference strengths as well. In a choice experiment, we presented 40 nine-year-old girls and their mothers and 40 twelve-year-old girls and their mothers with pairs of women's and girls' faces and asked the subjects to pick the face that appeared prettier to them. Preference frequencies and simple attractiveness scales derived from these preference frequencies by fitting the Bradley-Terry-Luce rule (Luce, D. R. (1959). Individual choice behavior: a theoretical analysis. New York: Wiley) were compared across subject groups. For the women's faces, we found no difference in preferences between nine-year-olds, twelve-year-olds, and adults, neither in direction nor in strength. For the girls' faces, we also found no major differences in preference direction, however, we did find reliable differences in preference strengths. To a considerable part these differences were due to the fact that the children showed less pronounced preferences between face stimuli than the adults. These results suggest a role of developmental factors in the perception of facial attractiveness.     

When facial attractiveness is only skin deep

Whilst the relationship between aspects of facial shape and attractiveness has been extensively studied, few studies have investigated which characteristics of the surface of faces positively influence attractiveness judgments. As many researchers have proposed a link between attractiveness and traits that appear healthy, apparent health of facial skin might be a property of the surface of faces that positively influences attractiveness judgments. In experiment 1 we tested for a positive correlation between ratings of the apparent health of small skin patches (extracted from the left and right cheeks of digital face images) and ratings of the attractiveness of male faces. By using computer-graphics faces, in experiment 2 we aimed to establish if apparent health of skin influences male facial attractiveness independently of shape information. Results suggest that apparent health of facial skin is correlated both with ratings of male facial attractiveness (experiment 1) and with being a visual cue for judgments of the attractiveness of male faces (experiment 2). These findings underline the importance of controlling for the influence of visible skin condition in studies of facial attractiveness and are consistent with the proposal that attractive physical traits are those that positively influence others' perceptions of an individual's health.     

Infant preferences for attractive faces: a cognitive explanation.

Research on infant face perception has shown that infants' preferences for attractive faces exist well before socialization from parents, peers, and the media can affect these preferences. Four studies assessed a cognitive explanation for the development of attractiveness preferences: cognitive averaging and infant preferences for mathematically averaged faces, or prototypes. Studies 1 and 2 demonstrated that both adults and 6-month-old infants prefer prototypical, mathematically averaged faces. Studies 3 and 4 demonstrated that 6-month-olds can abstract the central tendency from a group of naturalistic faces. Taken together, the studies suggest that infants' preferences for attractive faces can be explained by general information-processing mechanisms.     

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.     

The impact of face skin tone on perceived facial attractiveness: A study realized with an innovative methodology

This study aimed to assess the impact of target faces’ skin tone and perceivers’ skin tone on the participants’ attractiveness judgment regarding a symmetrical representative range of target faces as stimuli. Presented with a set of facial features, 240 Mozambican adults rated their attractiveness along a continuous scale. ANOVA and Chi-square were used to analyze the data. The results revealed that the skin tone of the target faces had an impact on the participants’ attractiveness judgment. Overall, participants preferred light-skinned faces over dark-skinned ones. This finding is not only consistent with previous results on skin tone preferences, but it is even more powerful because it demonstrates that the light skin tone preference occurs regardless of the symmetry and baseline attractiveness of the stimuli.     

Perceived health contributes to the attractiveness of facial symmetry, averageness, and sexual dimorphism

Symmetry, averageness, and sexual dimorphism (femininity in female faces, masculinity in male faces) are attractive in faces. Many have suggested that preferences for these traits may be adaptations for identifying healthy mates. If they are, then the traits should be honest indicators of health and their attractiveness should result from their healthy appearance. Much research has focused on whether these traits honestly signal health. Here we focused on whether the appeal of these traits results from their healthy appearance. Specifically, we tested whether the attractiveness of symmetry, averageness, and sexual dimorphism is reduced or eliminated when perceived health is controlled, in two large samples of Western faces and a large sample of Japanese faces. The appeal of symmetric faces was largely due to their healthy appearance, with most associations between symmetry and attractiveness eliminated when perceived health was controlled. A healthy appearance also contributed to the appeal of averageness and femininity in female faces and masculinity in male faces, although it did not fully explain their appeal. These results show that perceptions of attractiveness are sensitive to a healthy appearance, and are consistent with the hypothesis that preferences may be adaptations for mate choice.     

Integrating gaze direction and expression in preferences for attractive faces

Few studies have investigated how physical and social facial cues are integrated in the formation of face preferences. Here we show that expression differentially qualifies the strength of attractiveness preferences for faces with direct and averted gaze. For judgments of faces with direct gaze, attractiveness preferences were stronger for smiling faces than for faces with neutral expressions. By contrast, for judgments of faces with averted gaze, attractiveness preferences were stronger for faces with neutral expressions than for smiling faces. Because expressions can differ in meaning depending on whether they are directed toward or away from oneself, it is only by integrating gaze direction, facial expression, and physical attractiveness that one can unambiguously identify the most attractive individuals who are likely to reciprocate one's own social interest.     

Unattractive infant faces elicit negative affect from adults

We examined the relationship between infant attractiveness and adult affect by investigating whether differing levels of infant facial attractiveness elicit facial muscle movement correlated with positive and negative affect from adults (N = 87) using electromyography. Unattractive infant faces evoked significantly more corrugator supercilii and levator labii superioris movement (physiological correlates of negative affect) than attractive infant faces. These results suggest that unattractive infants may be at risk for negative affective responses from adults, though the relationship between those responses and caregiving behavior remains elusive.     

Dark traits: Sometimes hot,and sometimes not? Female preferences for Dark Triad faces depend on sociosexuality and contraceptive use

Although the Dark Triad personality (i.e., Machiavellianism, narcissism, and psychopathy) has been researched widely, only few studies have investigated women's preferences for men who present high and low Dark Triad features. With an on-line two-alternative forced choice questionnaire we investigated the interaction between preferences of 1962 Finnish women for facial stimuli that differed in the intensity of the Dark Triad traits, accounting for mating context, contraceptive use, and sexual openness (sociosexuality). Among non-contraceptive-using women, unrestricted sociosexuality was positively correlated with preference for high narcissistic male faces, whereas in contraceptive-using women, sociosexuality correlated negatively with preference for high Machiavellian male faces. We suggest that i) facial cues to Dark Triad traits are detectable by women, but ii) their effect on the judgments of attractiveness may vary depending on sociosexuality and contraceptive use, and that iii) preference for narcissism follows similar variation trends as masculinity preference, depending on sociosexuality and the use of hormonal contraception.     

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.     

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.