Testosterone-mediated sex differences in the face shape during adolescence: subjective impressions and objective features

Gender-Affirming Facial Surgery: Lower Third of the Face

This article is intended to give the reader an overview of facial gender-affirming procedures applicable to the lower face and neck. A review of facial analysis in the context of masculine versus feminine facial features and the contributions of both soft tissue and bone to this anatomy is provided. The use of systematic facial evaluation and patient-driven concerns as a guide for presurgical planning is reviewed. Detailed descriptions of the unique surgical interventions to feminize the soft tissues and the skeletal framework of the lower face and neck are provided.

Testosterone suppression impacts craniofacial growth structures during puberty : An animal study

AIM

Hormones play a crucial role in growth development; however, the impact of testosterone suppression (TS) on craniofacial growth during puberty remains inconclusive. This study aimed to evaluate the impact of TS during puberty on cephalometric measurements and histological characteristics of facial growth centers.

MATERIALS AND METHODS

Thirty-six heterogenic Wistar male rats were randomly allocated into experimental orchiectomy (ORX) and control (sham) groups. At an age of 23 days (prepubertal stage), orchiectomy and placebo surgery were performed. Cephalometric measurements were performed via lateral cephalograms during and after puberty. The animals were euthanized at an age of 45 days (pubertal stage) and 73 days (postpubertal stage). Histological slices of the growth centers (condyle, premaxilla, and median palatine suture) were stained with hematoxylin and eosin, and sirius red. Student's t or Mann-Whitney U tests were used to compare linear and angular cephalometric measurements across groups (α error = 5%).

RESULTS

Linear and angular measurements were statistically different in ORX animals (cranial bones, maxilla, and mandible) at 45 days and 73 days. Condylar histology showed a decrease in prechondroblast differentiation and a delay of mineralization in ORX animals. Vascularization of the medium palatine suture was lower in the ORX group at 45 days. Type I and III collagen fiber synthesis was lower in the ORX groups. In the premaxillary suture, collagen fibers were better organized in the sham groups.

CONCLUSIONS

Our results suggest that testosterone suppression affects craniofacial growth during puberty.

Congruence in European and Asian perception of Vietnamese facial attractiveness, averageness, symmetry and sexual dimorphism

Attractiveness is a proposed universal cue to overall biological quality. Nonetheless, local raters and raters of the same ethnicity may be more accurate in assessing the cues for attractiveness than distant and unfamiliar raters. Shared ethnicity and shared environment may both affect rating accuracy: our aim was to compare their relative influence. Therefore, we photographed young Vietnamese participants (N = 93, 33 women) from Hanoi, Vietnam. The photographs were rated by Czechs, Asian Vietnamese, and Czech Vietnamese (raters of Vietnamese origin who lived in Czechia for all or most of their life). Using geometric morphometrics, we measured facial shape cues to biological quality: averageness, asymmetry, and sexual dimorphism. We expected that Vietnamese raters residing in Czechia and Vietnam would agree on perceived attractiveness and use shape-related facial cues to biological quality better than Czech European raters, who are less familiar with East Asians. Surprisingly, mixed-effect models and post hoc comparisons identified no major cross-group differences in attributed attractiveness and path analyses revealed that the three groups based their rating on shape-related characteristics in a similar way. However, despite the considerable cross-cultural agreement regarding perceived attractiveness, Czech European raters associated attractiveness with facial shape averageness significantly more than Vietnamese raters.

Does the primate face cue personality?

When looking at others, primates primarily focus on the face - detecting the face first and looking at it longer than other parts of the body. This is because primate faces, even without expression, convey trait information crucial for navigating social relationships. Recent studies on primates, including humans, have linked facial features, specifically facial width-to-height ratio (fWHR), to rank and Dominance-related personality traits, suggesting these links' potential role in social decisions. However, studies on the association between dominance and fWHR report contradictory results in humans and variable patterns in nonhuman primates. It is also not clear whether and how nonhuman primates perceive different facial cues to personality traits and whether these may have evolved as social signals. This review summarises the variable facial-personality links, their underlying proximate and evolutionary mechanisms and their perception across primates. We emphasise the importance of employing comparative research, including various primate species and human populations, to disentangle phylogeny from socio-ecological drivers and to understand the selection pressures driving the facial-personality links in humans. Finally, we encourage researchers to move away from single facial measures and towards holistic measures and to complement perception studies using neuroscientific methods.

Influence of the nutritional status on facial morphology in young Japanese women

Evidence regarding the possible influence of nutritional status on the facial morphology has thus far been insufficient. We examined whether or not the physical body compositions and dietary behaviors were correlated with any morphological characteristics of the face. One hundred and fifteen young Japanese women participated. Variables representing the dietary behaviors were extracted from self-reported survey data, and corresponding three-dimensional (3D) facial images and body compositions were examined. Multivariate analyses identified significant relationships between the nutritional status and facial topography (p < 0.05). The clustering method revealed the existence of three dietary condition patterns ("balanced diet", "high-calorie-diet" with obesity tendency, and "imbalanced low-calorie-diet" with sarcopenic obesity tendency). Among these three patterns, a round face (increased facial width; analysis of variance [ANOVA], p < 0.05) was observed in the high-calorie-diet pattern, while the imbalanced low-calorie-diet pattern showed a more masculine face (increased face height, decreased eye height, increased non-allometric sexual shape differences; ANOVA, p < 0.05), thus suggesting the possibility of sex-hormonal influences. In summary, the body composition and dietary behaviors were found to influence the facial morphology, and potential biological influences were discussed.

Demographic and sociocultural predictors of face image satisfaction: The U.S. Body Project I

Despite substantial literature surrounding how people process and perceive faces, there is very little research investigating how people evaluate their own faces. We examined how gender, body mass, race, age, and sexual orientation were linked to people's satisfaction with the appearance of their eyes, nose, facial shape, and face overall among 11,620 adults recruited via Mechanical Turk. Most people mostly or definitely agreed they were happy with their facial appearance. There were notable racial differences, with Asian participants tending to report greater dissatisfaction. For example, only 66% of Asian women and 60% of Asian men mostly or definitely agreed that they were happy with the appearance of their eyes, which was lower than other racial groups. BMI and age were not strongly associated with face satisfaction. Sexual minority men were less satisfied than heterosexual men. About one in four gay and bisexual men, compared to only one in seven heterosexual men, reported dissatisfaction with their overall facial appearance. Men and women with poorer face image engaged in more appearance surveillance, more strongly internalized the thin-ideal, and perceived stronger sociocultural pressures from peers, parents, and media. The current study highlights important sociocultural and demographic factors tied to poorer face image.

Africans and Europeans differ in their facial perception of dominance and sex-typicality: a multidimensional Bayesian approach

Biosocial impact of facial dominance and sex-typicality is well-evidenced in various human groups. It remains unclear, though, whether perceived sex-typicality and dominance can be consistently predicted from sexually dimorphic facial features across populations. Using a combination of multidimensional Bayesian approach and geometric morphometrics, we explored associations between perceived dominance, perceived sex-typicality, measured sexual shape dimorphism, and skin colour in a European and an African population. Unlike previous studies, we investigated the effect of facial variation due to shape separately from variation due to visual cues not related to shape in natural nonmanipulated stimuli. In men, perceived masculinity was associated with perceived dominance in both populations. In European women higher perceived femininity was, surprisingly, likewise positively associated with perceived dominance. Both shape and non-shape components participate in the constitution of facial sex-typicality and dominance. Skin colour predicted perceived sex-typicality in Africans but not in Europeans. Members of each population probably use different cues to assess sex-typicality and dominance. Using our methods, we found no universal sexually dimorphic scale predicting human perception of sex-typicality and dominance. Unidimensional understanding of sex-typicality thus seems problematic and should be applied with cautions when studying perceived sex-typicality and its correlates.

Facial width-to-height ratio predicts fighting success: A direct replication and extension of Zilioli et al. (2014)

Zilioli et al. (2014) were the first to show an association between male facial width‐to‐height ratio (fWHR) and physical aggression and fighting ability in professional mixed‐martial‐arts fighters. Here, we re‐examined this relationship by replicating (using all original measures) and extending (using 23 new variables related to fighting performance) Zilioli et al. (2014) in a statistically well‐powered sample of 520 fighters using automatic and manual measures of the fWHR involving both eyelid and eyebrow landmarks, used interchangeably in previous reports (Studies 1–2). Most importantly, we successfully replicated Zilioli et al.'s (2014) central finding that fighters' fWHR, when manually calculated using the eyebrow landmark, predicted their fighting success (p = .004, controlling for body mass index and total fights). Consistent with past criticisms of using fight rather than fighter data to examine fighting success, which have argued that individual fights can be suddenly and unexpectedly determined and do not capture an individual's overall ability to succeed, Study 3 (N = 1367 fights) found no association between fWHR and singular victories. Studies 1–3 showed continual evidence that larger fWHRs were associated with grappling abilities, even after controlling for demographic and allometric factors. Strikingly, Study 3 discovered associations between all fWHR measures and grappling skill that remained robust before and after controlling for 17 different control variables. We discuss that grappling, or the act of taking down an opponent, involves a more aggressive, close‐combat approach than does striking. Combined, these results offer additional support for the argument that fWHR may have been shaped by sexual selection.

ESSM Position Statement "Sexual Wellbeing After Gender Affirming Surgery"

Introduction

Much has been published on the surgical and functional results following Gender Affirming Surgery (‘GAS’) in trans individuals. Comprehensive results regarding sexual wellbeing following GAS, however, are generally lacking.

Aim

To review the impact of various GAS on sexual wellbeing in treatment seeking trans individuals, and provide a comprehensive list of clinical recommendations regarding the various surgical options of GAS on behalf of the European Society for Sexual Medicine.

Methods

The Medline, Cochrane Library and Embase databases were reviewed on the results of sexual wellbeing after GAS.

Main Outcomes Measure

The task force established consensus statements regarding the somatic and general requirements before GAS and of GAS: orchiectomy-only, vaginoplasty, breast augmentation, vocal feminization surgery, facial feminization surgery, mastectomy, removal of the female sexual organs, metaidoioplasty, and phalloplasty. Outcomes pertaining to sexual wellbeing- sexual satisfaction, sexual relationship, sexual response, sexual activity, enacted sexual script, sexuality, sexual function, genital function, quality of sex life and sexual pleasure- are provided for each statement separately.

Results

The present position paper provides clinicians with statements and recommendations for clinical practice, regarding GAS and their effects on sexual wellbeing in trans individuals. These data, are limited and may not be sufficient to make evidence-based recommendations for every surgical option. Findings regarding sexual wellbeing following GAS were mainly positive. There was no data on sexual wellbeing following orchiectomy-only, vocal feminization surgery, facial feminization surgery or the removal of the female sexual organs. The choice for GAS is dependent on patient preference, anatomy and health status, and the surgeon's skills. Trans individuals may benefit from studies focusing exclusively on the effects of GAS on sexual wellbeing.

Conclusion

The available evidence suggests positive results regarding sexual wellbeing following GAS. We advise more studies that underline the evidence regarding sexual wellbeing following GAS. This position statement may aid both clinicians and patients in decision-making process regarding the choice for GAS. Özer M, Toulabi SP, Fisher AD, et al. ESSM Position Statement “Sexual Wellbeing After Gender Affirming Surgery”. Sex Med 2022;10:100471.

The Association Between Facial Width-to-Height Ratio (fWHR) and Sporting Performances: Evidence From Professional Basketball Players in Japan

Previous research in evolutionary psychology has highlighted the potential role of facial structures in explaining human behavior. The facial width-to-height ratio (fWHR) was found to be associated with testosterone-driven behavioral tendencies like achievement drive, aggression, and sporting success. The current study aimed to replicate such relationships using real-world data (i.e., professional basketball players; N = 482). Achievement drive, aggression, and sporting success were operationalized as field-goal attempts (FGA), the number of fouls committed (Foul), and player performance rating (EFF), respectively. The results indicated that fWHR was significantly associated with FGA and EFF, controlling for minutes of play and body-mass-index. The same results were obtained for separate analyses focusing on outsider players. However, analyses of inside players demonstrated that fWHR was associated only with EFF. The current research further provides empirical evidence supporting the effects of fWHR on achievement drive and sporting successes, although the effect sizes are notably small.

Masculinity and Lying

Dishonesty in communication has important economic implications. The standing literature has shown that lying is less pervasive than predicted by standard economic theory. We explore whether biology can help to explain this behavior. In a sample of men, we study whether masculine traits are related to (dis)honesty in a sender-receiver game. We study three masculine physical traits: the second-to-fourth digit ratio, facial morphometric masculinity and the facial width-to-height ratio. These biomarkers display significant associations with lying and deception in the game. We also explore the extent to which these effects operate through social preferences or through beliefs about the behavior of receivers.

Facial attractiveness and preference of sexual dimorphism: A comparison across five populations

Despite intensive research, evolutionary psychology has not yet reached a consensus regarding the association between sexual dimorphism and attractiveness. This study examines associations between perceived and morphological facial sexual dimorphism and perceived attractiveness in samples from five distant countries (Cameroon, Colombia, Czechia, Iran and Turkey). We also examined possible moderating effects of skin lightness, averageness, age, body mass and facial width. Our results suggest that in all samples, women's perceived femininity was positively related to their perceived attractiveness. Women found perceived masculinity in men attractive only in Czechia and Colombia, two distant populations. The association between perceived sexual dimorphism and attractiveness is thus potentially universal only for women. Across populations, morphological sexual dimorphism and averageness are not universally associated with either perceived facial sexual dimorphism or attractiveness. With our exploratory approach, results highlight the need for control of which measure of sexual dimorphism is used (perceived or measured) because they affect perceived attractiveness differently. Morphological averageness and sexual dimorphism are not good predictors of perceived attractiveness. It is noted that future studies should use samples from multiple populations to allow for identification of specific effects of local environmental and socioeconomic conditions on preferred traits in unmanipulated local facial stimuli.

Was facial width-to-height ratio subject to sexual selection pressures? A life course approach

Sexual selection researchers have traditionally focused on adult sex differences; however, the schedule and pattern of sex-specific ontogeny can provide insights unobtainable from an exclusive focus on adults. Recently, it has been debated whether facial width-to-height ratio (fWHR; bi-zygomatic breadth divided by midface height) is a human secondary sexual characteristic (SSC). Here, we review current evidence, then address this debate using ontogenetic evidence, which has been under-explored in fWHR research. Facial measurements were collected from 3D surface images of males and females aged 3 to 40 (Study 1; US European-descent, n = 2449), and from 2D photographs of males and females aged 7 to 21 (Study 2; Bolivian Tsimane, n = 179), which were used to calculate three fWHR variants (which we call fWHRnasion, fWHRstomion, and fWHRbrow) and two other common facial masculinity ratios (facial width-to-lower-face-height ratio, fWHRlower, and cheekbone prominence). We test whether the observed pattern of facial development exhibits patterns indicative of SSCs, i.e., differential adolescent growth in either male or female facial morphology leading to an adult sex difference. Results showed that only fWHRlower exhibited both adult sex differences as well as the classic pattern of ontogeny for SSCs-greater lower-face growth in male adolescents relative to females. fWHRbrow was significantly wider among both pre- and post-pubertal males in the Bolivian Tsimane sample; post-hoc analyses revealed that the effect was driven by large sex differences in brow height, with females having higher placed brows than males across ages. In both samples, all fWHR measures were inversely associated with age; that is, human facial growth is characterized by greater relative elongation in the mid-face and lower face relative to facial width. This trend continues even into middle adulthood. BMI was also a positive predictor of most of the ratios across ages, with greater BMI associated with wider faces. Researchers collecting data on fWHR should target fWHRlower and fWHRbrow and should control for both age and BMI. Researchers should also compare ratio approaches with multivariate techniques, such as geometric morphometrics, to examine whether the latter have greater utility for understanding the evolution of facial sexual dimorphism.

Assessment of Facial Morphologic Features in Patients With Congenital Adrenal Hyperplasia Using Deep Learning

IMPORTANCE

Congenital adrenal hyperplasia (CAH) is the most common primary adrenal insufficiency in children, involving excess androgens secondary to disrupted steroidogenesis as early as the seventh gestational week of life. Although structural brain abnormalities are seen in CAH, little is known about facial morphology.

OBJECTIVE

To investigate differences in facial morphologic features between patients with CAH and control individuals with use of machine learning.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study was performed at a pediatric tertiary center in Southern California, from November 2017 to December 2019. Patients younger than 30 years with a biochemical diagnosis of classical CAH due to 21-hydroxylase deficiency and otherwise healthy controls were recruited from the clinic, and face images were acquired. Additional controls were selected from public face image data sets.

MAIN OUTCOMES AND MEASURES

The main outcome was prediction of CAH, as performed by machine learning (linear discriminant analysis, random forests, deep neural networks). Handcrafted features and learned representations were studied for CAH score prediction, and deformation analysis of facial landmarks and regionwise analyses were performed. A 6-fold cross-validation strategy was used to avoid overfitting and bias.

RESULTS

The study included 102 patients with CAH (62 [60.8%] female; mean [SD] age, 11.6 [7.1] years) and 59 controls (30 [50.8%] female; mean [SD] age, 9.0 [5.2] years) from the clinic and 85 controls (48 [60%] female; age, <29 years) from face databases. With use of deep neural networks, a mean (SD) AUC of 92% (3%) was found for accurately predicting CAH over 6 folds. With use of classical machine learning and handcrafted facial features, mean (SD) AUCs of 86% (5%) in linear discriminant analysis and 83% (3%) in random forests were obtained for predicting CAH over 6 folds. There was a deviation of facial features between groups using deformation fields generated from facial landmark templates. Regionwise analysis and class activation maps (deep learning of regions) revealed that the nose and upper face were most contributory (mean [SD] AUC: 69% [17%] and 71% [13%], respectively).

CONCLUSIONS AND RELEVANCE

The findings suggest that facial morphologic features in patients with CAH is distinct and that deep learning can discover subtle facial features to predict CAH. Longitudinal study of facial morphology as a phenotypic biomarker may help expand understanding of adverse lifespan outcomes for patients with CAH.

Mating Strategies and the Masculinity Paradox: How Relationship Context, Relationship Status, and Sociosexuality Shape Women's Preferences for Facial Masculinity and Beardedness

According to the dual mating strategy model, in short-term mating contexts women should forego paternal investment qualities in favor of mates with well-developed secondary sexual characteristics and dominant behavioral displays. We tested whether this model explains variation in women's preferences for facial masculinity and beardedness in male faces. Computer-generated composites that had been morphed to appear ± 50% masculine were rated by 671 heterosexual women (M age = 31.72 years, SD = 6.43) for attractiveness when considering them as a short-term partner, long-term partner, a co-parent, or a friend. They then completed the Revised Sociosexual Inventory (SOI-R) to determine their sexual openness on dimensions of desire, behavior, and attitudes. Results showed that women's preferences were strongest for average facial masculinity, followed by masculinized faces, with feminized faces being least attractive. In contrast to past research, facial masculinity preferences were stronger when judging for co-parenting partners than for short-term mates. Facial masculinity preferences were also positively associated with behavioral SOI, negatively with desire, and were unrelated to global or attitudinal SOI. Women gave higher ratings for full beards than clean-shaven faces. Preferences for beards were higher for co-parenting and long-term relationships than short-term relationships, although these differences were not statistically significant. Preferences for facial hair were positively associated with global and attitudinal SOI, but were unrelated to behavioral SOI and desire. Although further replication is necessary, our findings indicate that sexual openness is associated with women's preferences for men's facial hair and suggest variation in the association between sociosexuality and women's facial masculinity preferences.

Physiological and perceptual correlates of masculinity in children's voices

Low frequency components (i.e. a low pitch (F0) and low formant spacing (ΔF)) signal high salivary testosterone and height in adult male voices and are associated with high masculinity attributions by unfamiliar listeners (in both men and women). However, the relation between the physiological, acoustic and perceptual dimensions of speakers' masculinity prior to puberty remains unknown. In this study, 110 pre-pubertal children (58 girls), aged 3 to 10, were recorded as they described a cartoon picture. 315 adults (182 women) rated children's perceived masculinity from the voice only after listening to the speakers' audio recordings. On the basis of their voices alone, boys who had higher salivary testosterone levels were rated as more masculine and the relation between testosterone and perceived masculinity was partially mediated by F0. The voices of taller boys were also rated as more masculine, but the relation between height and perceived masculinity was not mediated by the considered acoustic parameters, indicating that acoustic cues other than F0 and ΔF may signal stature. Both boys and girls who had lower F0, were also rated as more masculine, while ΔF did not affect ratings. These findings highlight the interdependence of physiological, acoustic and perceptual dimensions, and suggest that inter-individual variation in male voices, particularly F0, may advertise hormonal masculinity from a very early age.

A multivariate analysis of women's mating strategies and sexual selection on men's facial morphology

The strength and direction of sexual selection via female choice on masculine facial traits in men is a paradox in human mate choice research. While masculinity may communicate benefits to women and offspring directly (i.e. resources) or indirectly (i.e. health), masculine men may be costly as long-term partners owing to lower paternal investment. Mating strategy theory suggests women's preferences for masculine traits are strongest when the costs associated with masculinity are reduced. This study takes a multivariate approach to testing whether women's mate preferences are context-dependent. Women (n = 919) rated attractiveness when considering long-term and short-term relationships for male faces varying in beardedness (clean-shaven and full beards) and facial masculinity (30% and 60% feminized, unmanipulated, 30% and 60% masculinized). Participants then completed scales measuring pathogen, sexual and moral disgust, disgust towards ectoparasites, reproductive ambition, self-perceived mate value and the facial hair in partners and fathers. In contrast to past research, we found no associations between pathogen disgust, self-perceived mate value or reproductive ambition and facial masculinity preferences. However, we found a significant positive association between moral disgust and preferences for masculine faces and bearded faces. Preferences for beards were lower among women with higher ectoparasite disgust, providing evidence for ectoparasite avoidance hypothesis. However, women reporting higher pathogen disgust gave higher attractiveness ratings for bearded faces than women reporting lower pathogen disgust, providing support for parasite-stress theories of sexual selection and mate choice. Preferences for beards were also highest among single and married women with the strongest reproductive ambition. Overall, our results reflect mixed associations between individual differences in mating strategies and women's mate preferences for masculine facial traits.

Morphometric traits predict educational attainment independently of socioeconomic background

Background

Aim of this study is to describe the relationship between anthropometric traits and educational attainment among Estonian schoolchildren born between 1937 and 1962. We asked whether height, cranial volume and face width (a testosterone-dependent trait), measured in childhood predict later educational attainment independently of each other, family socioeconomic position (SEP) and sex. Associations between morphometric traits and education and their interactions with biosocial variables are of scholarly importance because higher education is nearly universally associated with low fertility in women, and often with high fertility in men. Hence, morphometric traits associated with educational attainment are targeted by natural selection and describing the exact nature of these associations is relevant for understanding the current patterns of evolution of human body size.

Methods

Data on morphometric measurements and family background of 11,032 Estonian schoolchildren measured between seven and 19 years of age were obtained from the study performed by Juhan Aul between 1956 and 1969. Ordinal logistic regression was used for testing the effects of morphometric traits, biosocial variables and their interaction on the cumulative probability of obtaining education beyond primary level.

Results

Of biosocial variables, family SEP was the most important determinant of educational attainment, followed by the sex, rural vs urban origin and the number of siblings. No significant interactions with morphometric traits were detected, i.e., within each category of SEP, rural vs urban origin and sex, taller children and those with larger heads and relatively narrower faces were more likely to proceed to secondary and/or tertiary education. The effect of height on education was independent of cranial volume, indicating that taller children did not obtain more educations because their brains were larger than those of shorter children; height per se was important.

Conclusions

Our main finding – that adjusting for other morphometric traits and biosocial variables, morphometric traits still robustly predicted educational attainment, is relevant for understanding the current patterns of evolution of human body size. Our findings suggest that fecundity selection acting on educational attainment could be partly responsible for the concurrent selection for smaller stature and cranial volume in women and opposite trends in men.

Facial features and unethical behavior - Doped athletes show higher facial width-to-height ratios than non-doping sanctioned athletes

Past research has emphasized the role of facial structures in predicting social behavior. In particular the facial width-to-height ratio (fWHR) was found to be a reliable predictor for antisocial and unethical behavior. The current study was aimed at examining this association in the field of sports: FWHRs of 146 doping sanctioned athletes in athletics (37 male/38 female) and weightlifting (44 male/27 female) were compared to the fWHRs of randomly chosen non-doping sanctioned athletes of the Top Ten at the World Championship 2017 and Olympic Games 2016 in both sports (146 athletes). The results showed that doping sanctioned athletes due to the use of anabolic steroids had larger fWHRs than non-doping sanctioned athletes. However, doping sanctioned athletes due to other doping rule violations than the use of anabolic steroids, did not show this effect. The study provides empirical evidence for the relation between fWHR and unethical behavior in a real-world setting and contributes to the discussion about fWHR’s biological origin, emphasizing the role of anabolic steroids. A mutual interaction between fWHR and doping behavior is discussed, at which a larger fWHR might signify a higher tendency to behave unethically, whereas the consequential intake of anabolic steroids might also shape individuals’ faces.

Honest Signals of Status: Facial and Bodily Dominance Are Related to Success in Physical but Not Nonphysical Competition

Recent studies suggest that both facial and bodily dominance promote high status positions and predict status-seeking behaviors such as aggression and social dominance. An evolutionarily relevant context in which associations between these dominance signals and status outcomes may be prevalent are face-to-face status contests. The present study examined whether facial and bodily dominance predicted success in dyadic competitions (one physical discipline, arm wrestling, and three nonphysical disciplines) in men (N = 125) in a controlled laboratory setting. Men's bodies and faces were independently rated for physical dominance, and associations of these ratings with contest outcomes as well as mediating and moderating variables (such as physical strength, body height, trait dominance, baseline and reactive testosterone) were examined. Both facial and bodily dominance positively predicted success in the physical discipline, mediated by physical strength, but not in the three nonphysical disciplines. Our findings demonstrate that facial and bodily physical dominance may be honest signals for men's formidability and hence status potential, at least in a physically competitive context.

Mothers are sensitive to men's beards as a potential cue of paternal investment

Mating strategy theories assert that women's preferences for androgen dependent traits in men are stronger when the costs of reduced paternal investment are lowest. Past research has shown that preferences for facial masculinity are stronger among nulliparous and non-pregnant women than pregnant or parous women. In two studies, we examine patterns in women's preferences for men's facial hair - likely the most visually conspicuous and sexually dimorphic of men's secondary sexual traits - when evaluating men's masculinity, dominance, age, fathering, and attractiveness. Two studies were conducted among heterosexual pregnant women, mothers, non-contractive and contraceptive users. Study 1 used a between-subjects sample (N = 2103) and found that mothers had significantly higher preferences for beards when judging fathering than all other women. Pregnant women and mothers also judged beards as more masculine and older, but less attractive, than non-contractive and contraceptive users. Parous women judged beards higher for age, masculinity and fathering, but lower for attractiveness, than nulliparous women. Irrespective of reproductive status, beards were judged as looking more dominant than clean-shaven faces. Study 2 used a within-subjects design (N = 53) among women surveyed during pregnancy and three months post-partum. Judgments of parenting skills were higher for bearded stimuli during pregnancy among women having their first baby, whereas among parous women parenting skills judgments for bearded stimuli were higher post-partum. Our results suggest that mothers are sensitive to beardedness as a masculine secondary sexual characteristic that may denote parental investment, providing evidence that women's mate preferences could reflect sexual selection for direct benefits.

The Influence of Body Composition Effects on Male Facial Masculinity and Attractiveness

Body mass index (BMI) and its facial correlates influence a range of perceptions including masculinity and attractiveness. BMI conflates body fat and muscle which are sexually dimorphic because men typically have more muscle but less fat than women. We therefore investigated the influence of facial correlates of body composition (fat mass and muscle mass) on the perception of masculinity in male faces. Women have been found to prefer more masculine looking men when considering short-term relationships compared with long-term relationships. We therefore conducted a second study of heterosexual women’s preferences for facial correlates of fat and muscle mass under long and short relationship contexts. We digitally transformed face shape simulating the effects of raised and lowered levels of body fat or muscle, controlling for each other, height and age. In Study 1, participants rated masculinity of shape-transformed male faces. The face shape correlates of muscle mass profoundly enhanced perceived masculinity but the face shape correlates of fat mass only affected the perception of masculinity in underweight to low normal weight men. In Study 2, we asked two groups of women to optimize male face images (by adjusting the shape correlates of fat and muscle) to most resemble someone they would prefer, either for a short-term sexual relationship or for a long-term relationship. The results were consistent across the two participant groups: women preferred the appearance of male faces associated with a higher muscle mass for short-term compared with long-term relationships. No difference was found in women’s preference for the face shape correlates of fat mass between the two relationship contexts. These findings suggest that the facial correlates of body fat and muscle have distinct impacts on the perception of male masculinity and on women’s preferences. The findings indicate that body composition needs to be taken into consideration in psychological studies involving body weight.

Facial masculinity does not appear to be a condition-dependent male ornament and does not reflect MHC heterozygosity in humans

Recent studies have called into question the idea that facial masculinity is a condition-dependent male ornament that indicates immunocompetence in humans. We add to this growing body of research by calculating an objective measure of facial masculinity/femininity using 3D images in a large sample (n = 1,233) of people of European ancestry. We show that facial masculinity is positively correlated with adult height in both males and females. However, facial masculinity scales with growth similarly in males and females, suggesting that facial masculinity is not exclusively a male ornament, as male ornaments are typically more sensitive to growth in males compared with females. Additionally, we measured immunocompetence via heterozygosity at the major histocompatibility complex (MHC), a widely-used genetic marker of immunity. We show that, while height is positively correlated with MHC heterozygosity, facial masculinity is not. Thus, facial masculinity does not reflect immunocompetence measured by MHC heterozygosity in humans. Overall, we find no support for the idea that facial masculinity is a condition-dependent male ornament that has evolved to indicate immunocompetence.

SNPs Associated With Testosterone Levels Influence Human Facial Morphology

Many factors influence human facial morphology, including genetics, age, nutrition, biomechanical forces, and endocrine factors. Moreover, facial features clearly differ between males and females, and these differences are driven primarily by the influence of sex hormones during growth and development. Specific genetic variants are known to influence circulating sex hormone levels in humans, which we hypothesize, in turn, affect facial features. In this study, we investigated the effects of testosterone-related genetic variants on facial morphology. We tested 32 genetic variants across 22 candidate genes related to levels of testosterone, sex hormone-binding globulin (SHGB) and dehydroepiandrosterone sulfate (DHEAS) in three cohorts of healthy individuals for which 3D facial surface images were available (Pittsburgh 3DFN, Penn State and ALSPAC cohorts; total n = 7418). Facial shape was described using a recently developed extension of the dense-surface correspondence approach, in which the 3D facial surface was partitioned into a set of 63 hierarchically organized modules. Each variant was tested against each of the facial surface modules in a multivariate genetic association-testing framework and meta-analyzed. Additionally, the association between these candidate SNPs and five facial ratios was investigated in the Pittsburgh 3DFN cohort. Two significant associations involving intronic variants of SHBG were found: both rs12150660 (p = 1.07E-07) and rs1799941 (p = 6.15E-06) showed an effect on mandible shape. Rs8023580 (an intronic variant of NR2F2-AS1) showed an association with the total and upper facial width to height ratios (p = 9.61E-04 and p = 7.35E-04, respectively). These results indicate that testosterone-related genetic variants affect normal-range facial morphology, and in particular, facial features known to exhibit strong sexual dimorphism in humans.

The role of mating context and fecundability in women's preferences for men's facial masculinity and beardedness

The ovulatory shift hypothesis proposes that women's preferences for masculine physical and behavioral traits are greater at the peri-ovulatory period than at other points of the menstrual cycle. However, many previous studies used self-reported menstrual cycle data to estimate fecundability rather than confirming the peri-ovulatory phase hormonally. Here we report two studies and three analyses revisiting the ovulatory shift hypothesis with respect to both facial masculinity and beardedness. In Study 1, a large sample of female participants (N = 2,161) self-reported their cycle phase and provided ratings for faces varying in beardedness (clean-shaven, light stubble, heavy stubble, full beards) and masculinity (-50%, -25%, natural, +25% and +50%) in a between-subjects design. In Study 2, 68 women provided the same ratings data, in a within-subjects design in which fertility was confirmed via luteinising hormone (LH) tests and analysed categorically. In Study 2, we also measured salivary estradiol (E) and progesterone (P) at the low and high fertility phases of the menstrual cycle among 36 of these women and tested whether shifts in E, P or E:P ratios predicted face preferences. Preferences for facial masculinity and beardedness did not vary as predicted with fecundability in Study 1, or with respect to fertility as confirmed via LH in Study 2. However, consistent with the ovulatory shift hypothesis, increasing E (associated with cyclical increases in fecundability) predicted increases in preferences for relatively more masculine faces; while high P (associated with cyclical decreases in fecundability) predicted increases in preferences for relatively more feminine faces. We also found an interaction between E and preferences for facial masculinity and beardedness, such that stubble was more attractive on un-manipulated than more masculine faces among women with high E. We consider discrepancies between our findings and those of other recent studies and suggest that closer scrutiny of the stimuli used to measure masculinity preferences across studies may help account for the many conflicting findings that have recently appeared regarding cycle phase preference shifts for facial masculinity.

Associations of physical strength with facial shape in an African pastoralist society, the Maasai of Northern Tanzania

OBJECTIVES

Previous research has documented associations of physical strength and facial morphology predominantly in men of Western societies. Faces of strong men tend to be more robust, are rounder and have a prominent jawline compared with faces of weak men. Here, we investigate whether the morphometric patterns of strength-face relationships reported for members of industrialized societies can also be found in members of an African pastoralist society, the Maasai of Northern Tanzania.

MATERIALS AND METHODS

Handgrip strength (HGS) measures and facial photographs were collected from a sample of 185 men and 120 women of the Maasai in the Ngorongoro Conservation Area. In young-adults (20-29 years; n = 95) and mid-adults (30-50 years; n = 114), we digitized 71 somatometric landmarks and semilandmarks to capture variation in facial morphology and performed shape regressions of landmark coordinates upon HGS. Results were visualized in the form of thin-plate plate spline deformation grids and geometric morphometric morphs.

RESULTS

Individuals with higher HGS tended to have wider faces with a lower and broader forehead, a wider distance between the medial canthi of the eyes, a wider nose, fuller lips, and a larger, squarer lower facial outline compared with weaker individuals of the same age-sex group. In mid-adult men, these associations were weaker than in the other age-sex groups.

DISCUSSION

We conclude that the patterns of HGS relationships with face shape in the Maasai are similar to those reported from related investigations in samples of industrialized societies. We discuss differences between the present and related studies with regard to knowledge about the causes for age- and sex-related facial shape variation and physical strength associations.

Procrustes-based geometric morphometrics on MRI images: An example of inter-operator bias in 3D landmarks and its impact on big datasets

Using 3D anatomical landmarks from adult human head MRIs, we assessed the magnitude of inter-operator differences in Procrustes-based geometric morphometric analyses. An in depth analysis of both absolute and relative error was performed in a subsample of individuals with replicated digitization by three different operators. The effect of inter-operator differences was also explored in a large sample of more than 900 individuals. Although absolute error was not unusual for MRI measurements, including bone landmarks, shape was particularly affected by differences among operators, with up to more than 30% of sample variation accounted for by this type of error. The magnitude of the bias was such that it dominated the main pattern of bone and total (all landmarks included) shape variation, largely surpassing the effect of sex differences between hundreds of men and women. In contrast, however, we found higher reproducibility in soft-tissue nasal landmarks, despite relatively larger errors in estimates of nasal size. Our study exemplifies the assessment of measurement error using geometric morphometrics on landmarks from MRIs and stresses the importance of relating it to total sample variance within the specific methodological framework being used. In summary, precise landmarks may not necessarily imply negligible errors, especially in shape data; indeed, size and shape may be differentially impacted by measurement error and different types of landmarks may have relatively larger or smaller errors. Importantly, and consistently with other recent studies using geometric morphometrics on digital images (which, however, were not specific to MRI data), this study showed that inter-operator biases can be a major source of error in the analysis of large samples, as those that are becoming increasingly common in the 'era of big data'.

A PCA-Based method for determining craniofacial relationship and sexual dimorphism of facial shapes

Previous studies have used principal component analysis (PCA) to investigate the craniofacial relationship, as well as sex determination using facial factors. However, few studies have investigated the extent to which the choice of principal components (PCs) affects the analysis of craniofacial relationship and sexual dimorphism. In this paper, we propose a PCA-based method for visual and quantitative analysis, using 140 samples of 3D heads (70 male and 70 female), produced from computed tomography (CT) images. There are two parts to the method. First, skull and facial landmarks are manually marked to guide the model's registration so that dense corresponding vertices occupy the same relative position in every sample. Statistical shape spaces of the skull and face in dense corresponding vertices are constructed using PCA. Variations in these vertices, captured in every principal component (PC), are visualized to observe shape variability. The correlations of skull- and face-based PC scores are analysed, and linear regression is used to fit the craniofacial relationship. We compute the PC coefficients of a face based on this craniofacial relationship and the PC scores of a skull, and apply the coefficients to estimate a 3D face for the skull. To evaluate the accuracy of the computed craniofacial relationship, the mean and standard deviation of every vertex between the two models are computed, where these models are reconstructed using real PC scores and coefficients. Second, each PC in facial space is analysed for sex determination, for which support vector machines (SVMs) are used. We examined the correlation between PCs and sex, and explored the extent to which the choice of PCs affects the expression of sexual dimorphism. Our results suggest that skull- and face-based PCs can be used to describe the craniofacial relationship and that the accuracy of the method can be improved by using an increased number of face-based PCs. The results show that the accuracy of the sex classification is related to the choice of PCs. The highest sex classification rate is 91.43% using our method.

Hypermasculinised facial morphology in boys and girls with Autism Spectrum Disorder and its association with symptomatology

Elevated prenatal testosterone exposure has been associated with Autism Spectrum Disorder (ASD) and facial masculinity. By employing three-dimensional (3D) photogrammetry, the current study investigated whether prepubescent boys and girls with ASD present increased facial masculinity compared to typically-developing controls. There were two phases to this research. 3D facial images were obtained from a normative sample of 48 boys and 53 girls (3.01-12.44 years old) to determine typical facial masculinity/femininity. The sexually dimorphic features were used to create a continuous 'gender score', indexing degree of facial masculinity. Gender scores based on 3D facial images were then compared for 54 autistic and 54 control boys (3.01-12.52 years old), and also for 20 autistic and 60 control girls (4.24-11.78 years). For each sex, increased facial masculinity was observed in the ASD group relative to control group. Further analyses revealed that increased facial masculinity in the ASD group correlated with more social-communication difficulties based on the Social Affect score derived from the Autism Diagnostic Observation Scale-Generic (ADOS-G). There was no association between facial masculinity and the derived Restricted and Repetitive Behaviours score. This is the first study demonstrating facial hypermasculinisation in ASD and its relationship to social-communication difficulties in prepubescent children.

Multiple regression analysis of the craniofacial region of Chinese Han people using linear and angular measurements based on MRI

The purpose of this study was to measure the craniofacial region of Chinese Han people in the linear and angular dimensions, and to analyse the effects on sex, age and body parameters (height and weight). All 250 individuals (86 males, 164 females) underwent a three-dimensional magnetic resonance imaging (MRI) scan, and the MRI data were imported into VG Studio MAX 2.2 software. Each linear and angular measurement in the craniofacial region was processed directly. Using SPSS 20.0 software, nine multiple regression equations were constructed, and all the adjusted R² values were statistically significant (0.031–0.311). Multiple regression analysis showed that most craniofacial measurements of Chinese people were significantly correlated with height, weight or age. The multiple regression equations constructed will be helpful in anthropometric analysis and forensic inference.

I Don't Like the Cut of your Jib: Perceived Facial Masculinity as a Cue to Criminality

Previous research has established that the appearance of criminal suspects and defendants can affect subsequent legal decisions. Specifically, researchers have proposed that (1) masculine suspects are believed to commit more stereotypically male crimes (e.g., burglary), (2) masculine suspects are believed to commit more violent crimes (e.g., assault), and (3) masculinity is a general cue for committing crime. The current study sought to test these competing hypotheses regarding masculine appearance and perceived criminality. Across three studies, participants read a brief crime scenario and were asked to select out of a lineup the suspect they believed had committed the crime. Suspect masculinity and type of crime were manipulated to determine whether the degree of masculinity influenced whether participants believed they had committed the crime. Results showed that participants consistently associated masculinity with committing violent crime and showed some evidence for the general criminality hypothesis on secondary measures. These findings have important implications regarding law enforcement, eyewitness and juror bias, and legal decisions.

Prenatal testosterone exposure is related to sexually dimorphic facial morphology in adulthood

Prenatal testosterone may have a powerful masculinizing effect on postnatal physical characteristics. However, no study has directly tested this hypothesis. Here, we report a 20-year follow-up study that measured testosterone concentrations from the umbilical cord blood of 97 male and 86 female newborns, and procured three-dimensional facial images on these participants in adulthood (range: 21-24 years). Twenty-three Euclidean and geodesic distances were measured from the facial images and an algorithm identified a set of six distances that most effectively distinguished adult males from females. From these distances, a 'gender score' was calculated for each face, indicating the degree of masculinity or femininity. Higher cord testosterone levels were associated with masculinized facial features when males and females were analysed together (n = 183; r = -0.59), as well as when males (n = 86; r = -0.55) and females (n = 97; r = -0.48) were examined separately (p-values < 0.001). The relationships remained significant and substantial after adjusting for potentially confounding variables. Adult circulating testosterone concentrations were available for males but showed no statistically significant relationship with gendered facial morphology (n = 85, r = 0.01, p = 0.93). This study provides the first direct evidence of a link between prenatal testosterone exposure and human facial structure.

Prenatal testosterone exposure is related to sexually dimorphic facial morphology in adulthood

Prenatal testosterone may have a powerful masculinizing effect on postnatal physical characteristics. However, no study has directly tested this hypothesis. Here, we report a 20-year follow-up study that measured testosterone concentrations from the umbilical cord blood of 97 male and 86 female newborns, and procured three-dimensional facial images on these participants in adulthood (range: 21-24 years). Twenty-three Euclidean and geodesic distances were measured from the facial images and an algorithm identified a set of six distances that most effectively distinguished adult males from females. From these distances, a 'gender score' was calculated for each face, indicating the degree of masculinity or femininity. Higher cord testosterone levels were associated with masculinized facial features when males and females were analysed together (n = 183; r = -0.59), as well as when males (n = 86; r = -0.55) and females (n = 97; r = -0.48) were examined separately (p-values < 0.001). The relationships remained significant and substantial after adjusting for potentially confounding variables. Adult circulating testosterone concentrations were available for males but showed no statistically significant relationship with gendered facial morphology (n = 85, r = 0.01, p = 0.93). This study provides the first direct evidence of a link between prenatal testosterone exposure and human facial structure.

The Curse of Curves: Sex Differences in the Associations Between Body Shape and Pain Expression

This study examines the associations between objective and subjective measurements and impressions of body shape and cold pressor pain reporting in healthy adults. On the basis of sexual selection theory (SST), we hypothesized that body characteristics that are universally preferred by the opposite sex-specifically, lower waist-to-hip ratios (WHR) in women and higher shoulder-to-hip ratios (SHR) in men-and characteristics (e.g., proportion of body fat in women) that infer attractiveness differently across cultures will correspond to higher experimental pain reporting in women and lower pain reporting in males. A convenience sample of young adults (n = 96, 58 females, 18-24 years; mean age = 19.4) was measured for body mass index (BMI), WHR, SHR, and subjective body impressions (SBI), along with cold pressor pain reporting. The findings showed that BMI was positively associated with WHR and less-positive SBI in both sexes. Consistent with SST, however, only BMI and WHR predicted variability in pain expression in women, whereas only SHR predicted variability in men. Subjective body impressions were positively associated with SHR among males and unrelated to WHR among females, yet only females showed a positive association between SBI and higher pain reporting. The findings suggest that sexually selected physical characteristics (WHR and SHR) and culturally influenced somatic (BMI) and psychological (SBI) indicators of attractiveness correspond with variability in pain reporting, potentially reflecting the general tendency for people to express clusters of sexually selected and culturally influenced traits that may include differential pain perception.

Development of facial sexual dimorphism in children aged between 12 and 15 years: a three-dimensional longitudinal study

OBJECTIVES

To evaluate sexual dimorphism of facial form and shape and to describe differences between the average female and male face from 12 to 15 years.

SETTING AND SAMPLE POPULATION

Overall 120 facial scans from healthy Caucasian children (17 boys, 13 girls) were longitudinally evaluated over a 4-year period between the ages of 12 and 15 years.

MATERIALS AND METHODS

Facial surface scans were obtained using a three-dimensional optical scanner Vectra-3D. Variation in facial shape and form was evaluated using geometric morphometric and statistical methods (DCA, PCA and permutation test). Average faces were superimposed, and the changes were evaluated using colour-coded maps.

RESULTS

There were no significant sex differences (p > 0.05) in shape in any age category and no differences in form in the 12- and 13-year-olds, as the female faces were within the area of male variability. From the age of 14, a slight separation occurred, which was statistically confirmed. The differences were mainly associated with size. Generally boys had more prominent eyebrow ridges, more deeply set eyes, a flatter cheek area, and a more prominent nose and chin area.

CONCLUSION

The development of facial sexual dimorphism during pubertal growth is connected with ontogenetic allometry.

Sexually dimorphic facial features vary according to level of autistic-like traits in the general population

BACKGROUND

In a recent study, Bejerot et al. observed that several physical features (including faces) of individuals with an autism spectrum disorder (ASD) were more androgynous than those of their typically developed counterparts, suggesting that ASD may be understood as a 'gender defiant' disorder. These findings are difficult to reconcile with the hypermasculinisation account, which proposes that ASD may be an exaggerated form of cognitive and biological masculinity. The current study extended these data by first identifying six facial features that best distinguished males and females from the general population and then examining these features in typically developing groups selected for high and low levels of autistic-like traits.

METHODS

In study 1, three-dimensional (3D) facial images were collected from 208 young adult males and females recruited from the general population. Twenty-three facial distances were measured from these images and a gender classification and scoring algorithm was employed to identify a set of six facial features that most effectively distinguished male from female faces. In study 2, measurements of these six features were compared for groups of young adults selected for high (n = 46) or low (n = 66) levels of autistic-like traits.

RESULTS

For each sex, four of the six sexually dimorphic facial distances significantly differentiated participants with high levels of autistic-like traits from those with low trait levels. All four features were less masculinised for high-trait males compared to low-trait males. Three of four features were less feminised for high-trait females compared to low-trait females. One feature was, however, not consistent with the general pattern of findings and was more feminised among females who reported more autistic-like traits. Based on the four significantly different facial distances for each sex, discriminant function analysis correctly classified 89.7% of the males and 88.9% of the females into their respective high- and low-trait groups.

CONCLUSIONS

The current data provide support for Bejerot et al.'s androgyny account since males and females with high levels of autistic-like traits generally showed less sex-typical facial features than individuals with low levels of autistic-like traits.

Saguenay Youth Study: a multi-generational approach to studying virtual trajectories of the brain and cardio-metabolic health

This paper provides an overview of the Saguenay Youth Study (SYS) and its parental arm. The overarching goal of this effort is to develop trans-generational models of developmental cascades contributing to the emergence of common chronic disorders, such as depression, addictions, dementia and cardio-metabolic diseases. Over the past 10 years, we have acquired detailed brain and cardio-metabolic phenotypes, and genome-wide genotypes, in 1029 adolescents recruited in a population with a known genetic founder effect. At present, we are extending this dataset to acquire comparable phenotypes and genotypes in the biological parents of these individuals. After providing conceptual background for this work (transactions across time, systems and organs), we describe briefly the tools employed in the adolescent arm of this cohort and highlight some of the initial accomplishments. We then outline in detail the phenotyping protocol used to acquire comparable data in the parents.

Modelling of facial growth in Czech children based on longitudinal data: Age progression from 12 to 15 years using 3D surface models

Dealing with the increasing number of long-term missing children and juveniles requires more precise and objective age progression techniques for the prediction of their current appearance. Our contribution includes detailed and real facial growth information used for modelling age progression during adolescence. This study was based on an evaluation of the overall 180 three-dimensional (3D) facial scans of Czech children (23 boys, 22 girls), which were longitudinally studied from 12 to 15 years of age and thus revealed the real growth-related changes. The boys underwent more marked changes compared with the girls, especially in the regions of the eyebrow ridges, nose and chin. Using modern geometric morphometric methods, together with their applications, we modelled the ageing and allometric trajectories for both sexes and simulated the age-progressed effects on facial scans. The facial parts that are important for facial recognition (eyes, nose, mouth and chin) all deviated less than 0.75mm, whereas the areas with the largest deviations were situated on the marginal parts of the face. The mean error between the predicted and real facial morphology obtained by modelling the children from 12 to 15 years of age was 1.92mm in girls and 1.86mm in boys. This study is beneficial for forensic artists as it reduces the subjectivity of age progression methods.

Identifying craniofacial features associated with prenatal exposure to androgens and testing their relationship with brain development

We used magnetic resonance (MR) images obtained in same-sex and opposite-sex dizygotic twins (n = 119, 8 years of age) to study possible effects of prenatal androgens on craniofacial features. Using a principal component analysis of 19 craniofacial landmarks placed on the MR images, we identified a principal component capturing craniofacial features that distinguished females with a presumed differential exposure to prenatal androgens by virtue of having a male (vs. a female) co-twin (Cohen's d = 0.76). Subsequently, we tested the possibility that this craniofacial "signature" of prenatal exposure to androgens predicts brain size, a known sexually dimorphic trait. In an independent sample of female adolescents (singletons; n = 462), we found that the facial signature predicts up to 8% of variance in brain size. These findings are consistent with the organizational effects of androgens on brain development and suggest that the facial signature derived in this study could complement other indirect measures of prenatal exposure to androgens.