Dimorphism In Faces Research Articles

Asexual individuals report high preferences for femininity in male and female faces

ABSTRACT Preferences for sexual dimorphism in male and female faces can vary based on the viewers’ gender, sexual orientation, and intensity of sexual desire. Asexual individuals, who experience little to no sexual attraction, may display different preferences for sexual dimorphism than has been observed in allosexual samples. Researchers have hypothesised that gender conformity may likewise impact preferences for sexual dimorphism. Participants (N = 182) recruited from an online asexual community provided demographic information and responded to measures of romantic attraction, sexual attraction, and conformity with male and female gender norms before they indicated their preference for male and female faces that were digitally altered to be more or less sexually dimorphic. Regardless of gender, asexual participants displayed a high preference for femininity in male and female faces. Preferences for sexual dimorphism displayed complex, and inconsistent associations with reported romantic and sexual attraction, and with conformity to feminine gender norms. This is the first report of preferences for facial sexual dimorphism and assessment of the role of gender conformity in an asexual population. This research adds to our understanding of the role of sexual attraction in predicting preferences for sexual dimorphism in faces.

The Autumn Years: Age Differences in Preferences for Sexually Dimorphic Faces.

Life history theory proposes that it is adaptive for older people to shift investment away from reproductive effort (such as mating) to survivorship. However, it remains unclear whether the shift is also present at the psychological level. We investigated this question by comparing preferences for mate choice-relevant cues, sexually dimorphic facial images, between older (60years and older, n = 92) and younger adults (18-40years, n = 86). Results showed that older adults had significantly smaller preferences for sexually dimorphic faces of both sexes than young adults. Specifically, both older men and women showed no significant preferences for sexually dimorphic traits when judging opposite-sex faces, and smaller preferences for masculine male faces and feminine female faces when judging same-sex faces. Young adults generally showed strong preferences for masculine male faces and feminine female faces. In Study 2, we confirmed that the absent/reduced preferences in older adults for sexually dimorphic faces did not result from poor visual ability. The smaller preferences for sexually dimorphic facial cues in older adults compared to young adults suggest that older adults may shift away from mating-oriented psychology as they become less fertile.

Heightened condition dependent expression of structural coloration in the faces, but not wings, of male and female flies.

Structurally colored sexual signals are a conspicuous and widespread class of ornament used in mate choice, though the extent to which they encode information on the quality of their bearers is not fully resolved. Theory predicts that signaling traits under strong sexual selection as honest indicators should evolve to be more developmentally integrated and exaggerated than nonsexual traits, thereby leading to heightened condition dependence. Here, we test this prediction through examination of the sexually dimorphic faces and wings of the cursorial fly Lispe cana. Males and females possess structural UV-white and golden faces, respectively, and males present their faces and wings to females during close-range, ground-based courtship displays, thereby creating the opportunity for mutual inspection. Across a field-collected sample of individuals, we found that the appearance of the faces of both sexes scaled positively with individual condition, though along separate axes. Males in better condition expressed brighter faces as modeled according to conspecific flies, whereas condition scaled with facial saturation in females. We found no such relationships for their wing interference pattern nor abdomens, with the latter included as a nonsexual control. Our results suggest that the structurally colored faces, but not the iridescent wings, of male and female L. cana are reliable guides to individual quality and support the broader potential for structural colors as honest signals. They also highlight the potential for mutual mate choice in this system, while arguing for 1 of several alternate signaling roles for wing interferences patterns among the myriad taxa which bear them.

Women\u2019s Preferences for Sexual Dimorphism in Faces: Data from a Sample of Arab Women

Many previous studies have investigated the effects of manipulating sexually dimorphic shape characteristics in face images on attractiveness judgments. However, results have been mixed and show considerable cross-cultural variability, particularly for women’s judgments of men’s facial attractiveness. Because very little research has investigated face preferences in Arab samples, we assessed Arab women’s preferences for sexually dimorphic face shapes (study 1) and the effect of sexually dimorphic face shapes on Arab women’s dominance perceptions (study 2). Analyses showed that Arab women preferred feminized versions of both women’s and men’s faces over masculinized versions (study 1, N = 272) and that masculinizing face shape had a positive effect on Arab women’s perceptions of the dominance of men, but not women (study 2, N = 270). These image manipulations did not have a significant effect on perceptions of trustworthiness, however (study 3, N = 434). Collectively, these results suggest that Arab women prefer relatively feminine face shapes in potential mates that they perceive as being low dominance. We discuss some directions for future research on the ultimate function of Arab women’s preferences for sexual dimorphism in faces

Immune function during early adolescence positively predicts adult facial sexual dimorphism in both men and women

Evolutionary theories suggest that humans prefer sexual dimorphism in faces because masculinity in men and femininity in women may be an indicator of immune function during development. In particular, the immunocompetence handicap hypothesis proposes that sexual dimorphism indicates good immune function during development because the sex hormones, particularly testosterone in men, required for the development of sexually dimorphic facial features also taxes the immune system. Therefore, only healthy males can afford the high level of testosterone for the development of sexually dimorphic traits without compromising their survival. Researchers have suggested that a similar mechanism via the effects of oestrogen might also explain male preferences for female femininity. Despite the prominence of the immunocompetence handicap hypothesis, no studies have tested whether immune function during development predicts adult facial sexual dimorphism. Here, using data from a longitudinal public health dataset, the Western Australian Pregnancy Cohort (Raine) Study (Generation 2), we show that some aspects of immune function during early adolescence (14 years) positively predict sexually dimorphic 3D face shape in both men and women. Our results support a fundamental assumption that facial sexual dimorphism is an indicator of immune function during the development of facial sexual dimorphism.

Androstadienone resulted in a rightward shift of women's preference for sexually dimorphic male faces across the continuum of femininity-masculinity

As a derivative of testosterone, androstadienone (AND) can influence human psychological and physiological states. To explore the influence of AND on women's preferences for male sexual dimorphic faces in a mate-choice context, we asked 52 females in the luteal phase to choose one from four sexual dimorphic male faces in a long-term and short-term context while inhaling 250 μm of AND or a placebo odor on two consecutive days. Results revealed that participants had a greater and lesser preference for the +30% masculinized and 60% feminized faces, respectively, while inhaling AND, as compared to when inhaling the placebo. The AND intervention resulted in a rightward shift of the women's preference for male sexual dimorphic faces across the continuum of femininity-masculinity. The current findings highlight that AND may influence women's preference for male sexually dimorphic faces in a mate-choice context.

Individual differences in preferences for sexual dimorphism in faces among Chinese adolescents in single-sex and mixed-sex environments

Research indicates that people often show a preference for familiar faces, and frequent exposure to a particular type of face can lead to the development of a preference for faces with similar features. Adolescents in single-sex environments are more likely to be exposed to same-sex faces and less likely to view faces of the opposite sex. This study aimed to examine whether the effects of gendered environments on facial feature preferences exist in a Chinese cultural context. We examined individual differences in preferences for sexual dimorphism in faces among Chinese adolescents in single-sex and mixed-sex environments (N = 1431 mean age = 18.1). We found that male students in single-sex environments preferred more masculinized female faces than their peers in mixed-sex environments. Furthermore, female students in single-sex environments preferred more feminized male faces than their peers in mixed-sex environments. There were no significant differences in preferences for same-sex faces between participants in single-sex and mixed-sex environments for both male and female students. These results provide cross-cultural evidence that frequent exposure to certain types of faces can influence people's preferences regarding sexual dimorphism in facial features. The findings indicated the effect of gendered environments on mating preferences in older adolescents.

Relationships between disgust sensitivity and trait preferences in gay men in China

Disgust can be thought of as a disease-avoidance mechanism. Previous studies indicated that pathogen disgust is correlated to preferences for sexual dimorphism in faces and voices in heterosexual women and men, as well as in gay men. In this study, we examined the associations between disgust sensitivity and preferences for five potential traits of romantic partners among gay men in China. Participants (N = 590) completed the three domains of Disgust Scale and rated their preferences for five partner-related traits: attractiveness, warmth, health, success, and masculinity. Pathogen disgust was positively correlated with stronger preferences for all traits. A moral disgust was positively correlated with stronger preferences for attractiveness, warmth, and health. Sexual disgust was negatively correlated with preferences for attractiveness, but was positively correlated with stronger preferences for masculinity. The results indicated the broad associations between disgust and mate/partner preference, including faces, voices, beardedness, and personality traits. The pattern of results was consistent with disease-avoidance hypothesis of disgust.

Effects of Sexually Dimorphic Shape Cues on Neurophysiological Correlates of Women’s Face Processing

Sexual dimorphism (i.e., masculinity in males and femininity in females) is known to affect social perceptions that are important for both mate choice and intrasexual competition, such as attractiveness and dominance. Little is known, however, about the neurophysiological underpinnings mediating sexual dimorphism’s effects on face processing. Here we investigate the neurological correlates of processing sexually dimorphic faces using event-related potentials (ERPs). We employed image transformation techniques to enhance and reduce the sexually dimorphic shape features of male and female faces viewed by women performing a sex categorization task. Sexual dimorphism modulated superior-central N250 magnitude and the peak latency of the N170 and P200. The sex of the face further modulated the amplitude of the P200. These findings extend prior work linking the superior-central N250 to social categorization processes triggered by face shape, and strengthen its functional interpretation in terms of coarse- versus fine-grained categorical judgements. We conclude that ERPs can illuminate the cognitive mechanisms (i.e., mental processes) underlying behavioral responses to sexual dimorphism.

Sexual dimorphism of facial width-to-height ratio in human skulls and faces: A meta-analytical approach

Facial width-to-height ratio (FWHR), defined as the width of the face divided by the upper facial height, is a cue to behaviour. Explanations for this link often involve the idea that FWHR is sexually dimorphic, resulting from intersexual selection pressures. However, few studies have considered sexual dimorphism in skulls since the original paper on this topic, and it is possible that different explanations may be required if faces show sex differences but skulls do not. Here, meta-analyses of skulls found that men did have larger FWHR than women, although this effect was small. However, after categorising samples by ethnicity and geographical origin, meta-analyses only found evidence of sex differences in East Asians, and again, this effect was small. A re-analysis of previous studies after excluding skull samples found little evidence of sexual dimorphism in faces. Again, considering ethnicities separately, I found no differences for White samples but a medium-sized effect with East Asians, although this was not statistically significant with only three samples. Taken together, I found no reason to consider FWHR as a sexually dimorphic measure in skulls or faces, at least not universally, and so accounts based upon this assumption need rethinking if researchers are to explain the relationship between FWHR and behaviour.

Variation in Women’s Preferences Regarding Male Facial Masculinity Is Better Explained by Genetic Differences Than by Previously Identified Context-Dependent Effects

Women’s preferences for masculine versus feminine male faces are highly variable. According to a dominant theory in evolutionary psychology, this variability results from adaptations that optimize preferences by calibrating them to certain contextual factors, including women’s self-perceived attractiveness, short- versus long-term relationship orientation, pathogen disgust sensitivity, and stage of the menstrual cycle. The theory does not account for the possible contribution of genetic variation on women’s facial masculinity preference. Using a large sample (N = 2,160) of identical and nonidentical female Finnish twins and their siblings, we showed that the proportion of variation in women’s preferences regarding male facial masculinity that was attributable to genetic variation (38%) dwarfed the variation due to the combined effect of contextual factors (< 1%). These findings cast doubt on the importance of these context-dependent effects and may suggest a need for refocusing in the field toward understanding the wide genetic variation in these preferences and how this variation relates to the evolution of sexual dimorphism in faces.

Sociosexuality and Relationship Status Interact to Predict Facial Symmetry Preferences

Past research demonstrates that the relationship between sociosexual orientation and “good genes” face preferences is moderated by participants’ own relationship status. Specifically, those women who are relatively sexually unrestricted demonstrate a greater preference for sexual dimorphism in faces, but only when unpartnered; for partnered women, sociosexuality does not predict preferences for sexual dimorphism. The current study extended these findings by assessing whether sociosexuality and relationship status interact to influence preferences for a different phenotypic cue, facial symmetry, in both male and female targets. A secondary hypothesis assessed whether this pattern of face preferences was moderated by either participant or target sex. Men and women completed a symmetry preference task, the sociosexual orientation inventory, and were asked to report their relationship status. Unrestricted sociosexual orientation predicted a heightened preference for facial symmetry in both male and female faces, but only in unpartnered participants. This effect was not qualified by participant gender. These findings provide additional evidence that an important moderating variable when assessing the association between mating personality (i.e., sociosexual orientation) and “good genes” face preferences is an individual’s own relationship status.

Similarities in Human Visual and Declared Measures of Preference for Opposite-Sex Faces

Facial appearance in humans is associated with attraction and mate choice. Numerous studies have identified that adults display directional preferences for certain facial traits including symmetry, averageness, and sexually dimorphic traits. Typically, studies measuring human preference for these traits examine declared (e.g., choice or ratings of attractiveness) or visual preferences (e.g., looking time) of participants. However, the extent to which visual and declared preferences correspond remains relatively untested. In order to evaluate the relationship between these measures we examined visual and declared preferences displayed by men and women for opposite-sex faces manipulated across three dimensions (symmetry, averageness, and masculinity) and compared preferences from each method. Results indicated that participants displayed significant visual and declared preferences for symmetrical, average, and appropriately sexually dimorphic faces. We also found that declared and visual preferences correlated weakly but significantly. These data indicate that visual and declared preferences for manipulated facial stimuli produce similar directional preferences across participants and are also correlated with one another within participants. Both methods therefore may be considered appropriate to measure human preferences. However, while both methods appear likely to generate similar patterns of preference at the sample level, the weak nature of the correlation between visual and declared preferences in our data suggests some caution in assuming visual preferences are the same as declared preferences at the individual level. Because there are positive and negative factors in both methods for measuring preference, we suggest that a combined approach is most useful in outlining population level preferences for traits.

Gender identity rather than sexual orientation impacts on facial preferences.

Differences in facial preferences between heterosexual men and women are well documented. It is still a matter of debate, however, how variations in sexual identity/sexual orientation may modify the facial preferences. This study aims to investigate the facial preferences of male-to-female (MtF) individuals with gender dysphoria (GD) and the influence of short-term/long-term relationships on facial preference, in comparison with healthy subjects. Eighteen untreated MtF subjects, 30 heterosexual males, 64 heterosexual females, and 42 homosexual males from university students/staff, at gay events, and in Gender Clinics were shown a composite male or female face. The sexual dimorphism of these pictures was stressed or reduced in a continuous fashion through an open-source morphing program with a sequence of 21 pictures of the same face warped from a feminized to a masculinized shape. An open-source morphing program (gtkmorph) based on the X-Morph algorithm. MtF GD subjects and heterosexual females showed the same pattern of preferences: a clear preference for less dimorphic (more feminized) faces for both short- and long-term relationships. Conversely, both heterosexual and homosexual men selected significantly much more dimorphic faces, showing a preference for hyperfeminized and hypermasculinized faces, respectively. These data show that the facial preferences of MtF GD individuals mirror those of the sex congruent with their gender identity. Conversely, heterosexual males trace the facial preferences of homosexual men, indicating that changes in sexual orientation do not substantially affect preference for the most attractive faces.

Human preferences for sexually dimorphic faces may be evolutionarily novel.

A large literature proposes that preferences for exaggerated sex typicality in human faces (masculinity/femininity) reflect a long evolutionary history of sexual and social selection. This proposal implies that dimorphism was important to judgments of attractiveness and personality in ancestral environments. It is difficult to evaluate, however, because most available data come from large-scale, industrialized, urban populations. Here, we report the results for 12 populations with very diverse levels of economic development. Surprisingly, preferences for exaggerated sex-specific traits are only found in the novel, highly developed environments. Similarly, perceptions that masculine males look aggressive increase strongly with development and, specifically, urbanization. These data challenge the hypothesis that facial dimorphism was an important ancestral signal of heritable mate value. One possibility is that highly developed environments provide novel opportunities to discern relationships between facial traits and behavior by exposing individuals to large numbers of unfamiliar faces, revealing patterns too subtle to detect with smaller samples.

Women's hormone levels modulate the motivational salience of facial attractiveness and sexual dimorphism.

The physical attractiveness of faces is positively correlated with both behavioral and neural measures of their motivational salience. Although previous work suggests that hormone levels modulate women's perceptions of others' facial attractiveness, studies have not yet investigated whether hormone levels also modulate the motivational salience of facial characteristics. To address this issue, we investigated the relationships between within-subject changes in women's salivary hormone levels (estradiol, progesterone, testosterone, and estradiol-to-progesterone ratio) and within-subject changes in the motivational salience of attractiveness and sexual dimorphism in male and female faces. The motivational salience of physically attractive faces in general and feminine female faces, but not masculine male faces, was greater in test sessions where women had high testosterone levels. Additionally, the reward value of sexually dimorphic faces in general and attractive female faces, but not attractive male faces, was greater in test sessions where women had high estradiol-to-progesterone ratios. These results provide the first evidence that the motivational salience of facial attractiveness and sexual dimorphism is modulated by within-woman changes in hormone levels.

Perceptions of Human Attractiveness Comprising Face and Voice Cues

In human mate choice, sexually dimorphic faces and voices comprise hormone-mediated cues that purportedly develop as an indicator of mate quality or the ability to compete with same-sex rivals. If preferences for faces communicate the same biologically relevant information as do voices, then ratings of these cues should correlate. Sixty participants (30 male and 30 female) rated a series of opposite-sex faces, voices, and faces together with voices for attractiveness in a repeated measures computer-based experiment. The effects of face and voice attractiveness on face-voice compound stimuli were analyzed using a multilevel model. Faces contributed proportionally more than voices to ratings of face-voice compound attractiveness. Faces and voices positively and independently contributed to the attractiveness of male compound stimuli although there was no significant correlation between their rated attractiveness. A positive interaction and correlation between attractiveness was shown for faces and voices in relation to the attractiveness of female compound stimuli. Rather than providing a better estimate of a single characteristic, male faces and voices may instead communicate independent information that, in turn, provides a female with a better assessment of overall mate quality. Conversely, female faces and voices together provide males with a more accurate assessment of a single dimension of mate quality.

Sex-Dimorphic Face Shape Preference in Heterosexual and Homosexual Men and Women

Studies have used manipulated faces to test the preferences of heterosexual individuals for sexually dimorphic facial cues. In contrast to previous studies, which have generally excluded homosexual participants, we directly compared homosexual and heterosexual male and female preferences for manipulated sexual dimorphism in faces (homosexual males: n=311; heterosexual males: n=215; homosexual females: n=159; heterosexual females: n=218). Prior studies on sexual orientation and preferences for faces that were paired with masculine and feminine behavioral descriptors suggest that homosexual men prefer more masculine men and that homosexual women demonstrate no preference for either masculinity or femininity in women. In our study, we tested for similarities and differences among heterosexual and homosexual males and females with regard to their preferences for a more specific aspect of faces: sexual dimorphism of face shape. Homosexual men demonstrated stronger preferences for masculinity in male faces than did all of the other groups. Homosexual women demonstrated stronger preferences for masculinity in female faces than did heterosexual women. These results suggest attractiveness judgments of same-sex faces made by homosexual individuals are not a mirror image of those made by heterosexual individuals of the opposite sex. Our data suggest that face preferences of homosexual individuals reflect a system of biologically and socially guided preferences at least as complex as those found among heterosexual individuals.

Short Article: Are Attractive Facial Characteristics Peculiar to the Sex of a Face?

Preferences for faces are thought to be the result of either general adaptations for mate selection, and thus influenced by sexual dimorphism, or mechanisms of general information processing and thus nonspecific to faces. If mate choice determines face preference then it should follow that the sex of a face should affect attractiveness judgements. To test this idea we used image morphing to generate three versions of face images: original, opposite sex, and antiface. First we established that the sex of the face was identifiable in our images. We then collected attractiveness ratings for the three face types. We found that attractiveness ratings to the original faces were correlated with, and did not differ significantly between, ratings to the opposite-sex faces. However, ratings for either the original or opposite face types were not correlated with and were significantly lower than ratings to the antifaces. Our findings failed to support the idea that attractiveness is related to sexual dimorphism in faces alone but suggest instead that other more generic factors influence preferences for all faces.

Symmetry Is Related to Sexual Dimorphism in Faces: Data Across Culture and Species

BackgroundMany animals both display and assess multiple signals. Two prominently studied traits are symmetry and sexual dimorphism, which, for many animals, are proposed cues to heritable fitness benefits. These traits are associated with other potential benefits, such as fertility. In humans, the face has been extensively studied in terms of attractiveness. Faces have the potential to be advertisements of mate quality and both symmetry and sexual dimorphism have been linked to the attractiveness of human face shape.Methodology/Principal FindingsHere we show that measurements of symmetry and sexual dimorphism from faces are related in humans, both in Europeans and African hunter-gatherers, and in a non-human primate. Using human judges, symmetry measurements were also related to perceived sexual dimorphism. In all samples, symmetric males had more masculine facial proportions and symmetric females had more feminine facial proportions.Conclusions/SignificanceOur findings support the claim that sexual dimorphism and symmetry in faces are signals advertising quality by providing evidence that there must be a biological mechanism linking the two traits during development. Such data also suggests that the signalling properties of faces are universal across human populations and are potentially phylogenetically old in primates.