Associations among facial masculinity, physical strength, fluctuating asymmetry and attractiveness in young men and women

Head poses and grimaces: Challenges for automated face identification algorithms?

In today's biometric and commercial settings, state-of-the-art image processing relies solely on artificial intelligence and machine learning which provides a high level of accuracy. However, these principles are deeply rooted in abstract, complex "black-box systems". When applied to forensic image identification, concerns about transparency and accountability emerge. This study explores the impact of two challenging factors in automated facial identification: facial expressions and head poses. The sample comprised 3D faces with nine prototype expressions, collected from 41 participants (13 males, 28 females) of European descent aged 19.96 to 50.89 years. Pre-processing involved converting 3D models to 2D color images (256 × 256 px). Probes included a set of 9 images per individual with head poses varying by 5° in both left-to-right (yaw) and up-and-down (pitch) directions for neutral expressions. A second set of 3,610 images per individual covered viewpoints in 5° increments from -45° to 45° for head movements and different facial expressions, forming the targets. Pair-wise comparisons using ArcFace, a state-of-the-art face identification algorithm yielded 54,615,690 dissimilarity scores. Results indicate that minor head deviations in probes have minimal impact. However, the performance diminished as targets deviated from the frontal position. Right-to-left movements were less influential than up and down, with downward pitch showing less impact than upward movements. The lowest accuracy was for upward pitch at 45°. Dissimilarity scores were consistently higher for males than for females across all studied factors. The performance particularly diverged in upward movements, starting at 15°. Among tested facial expressions, happiness and contempt performed best, while disgust exhibited the lowest AUC values.

Contextual modulation of the red-attractiveness effect: Differences in affiliation and competitive settings

Color is not just about aesthetics but also communicates specific information and has important implications for psychological functioning. It has been shown that the color red enhances perceived attractiveness when evaluating the opposite sex, which we call the red-attractiveness effect. However, few studies have attached importance to the social context in which attractiveness ratings are made, which means that the red-attractiveness effect is rarely explained by analyzing the role of social context. We conducted two experiments to test the red-attractiveness effect in Chinese culture and the influence of context (affiliation or competitive) on the red-attractiveness effect. Experiment 1 (160 Chinese college students, 80 males) showed that the opposite-sex target in red, compared to white, was rated more attractive, and the red-attractiveness effect was applicable to Chinese culture. Experiment 2 (480 Chinese college students, 240 males) found that perceived attractiveness was strengthened in the affiliation context and weakened in the competitive context, that is, the main effect of context was significant. We did not find any significant effect of the color red in either context, that is, the color main effect was not significant. However, the results indicate that red can enhance perceived attractiveness when evaluating the opposite sex. This study demonstrates that the red attractiveness effect may exist in different cultural backgrounds and contexts.

Facial Beauty and the Correlation of Associated Attributes: An Empirical Aesthetic Database Study

Background

The pursuit of understanding facial beauty has been the subject of scientific interest since time immemorial. How beauty is associated with other perceived attributes that affect human interaction remains elusive. This article aims to explore how facial attractiveness correlates with health, happiness, femininity, and perceived age. We review the existing literature and report an empirical study using expert raters.

Methods

A peer-reviewed database of 2870 aesthetic female faces with a global ethnic distribution was created. Twenty-one raters were asked to score frontal images on the attributes of health, happiness, femininity, perceived age, and attractiveness, on a Likert scale of 0-100.

Results

Pearson correlation coefficients ("r") were calculated to correlate attributes, with multiple regression analyses and P values calculated. Strong positive correlation was found between attractiveness and health (r = 0.61, P < 0.05), attractiveness and femininity (r = 0.7, P < 0.05), and health and femininity (r = 0.57, P < 0.05); medium positive correlation between health and happiness (r = 0.31, P < 0.05); and small positive correlation between happiness and femininity (r = 0.21, P < 0.05). A neutral relationship was observed between perceived age and happiness (0.01, P = 0.75), and medium negative correlation between perceived age and attractiveness (-0.32, P < 0.05), health (-0.36, P < 0.05), and femininity (-0.31, P < 0.05).

Conclusions

Our study illustrates a positive correlation between the positive attributes of health, happiness, femininity and attractiveness, with a negative correlation of all characteristics with increasing perceived age. This provides insight into the complexity of human interaction and provides a holistic view of attraction as being a gateway to the reflexive perception of other attributes. The implications encourage an aesthetic focus on facial reconstruction.

Facial cues to physical strength are not always associated with facial masculinity: Comparative study of Europeans and Southern Siberians

OBJECTIVES

The aim of our study was to compare morphometric patterns of facial sexual dimorphism with strength-face relationship in members of two distinct populations of European and Central Asian origin: Russians and Tuvans.

METHODS

Handgrip strength (HGS) measures and facial photographs were collected from Russian (n = 233) and Tuvan (n = 187) men and women. We digitized 70 landmarks and semilandmarks on full-face and 54 landmarks and semilandmarks on profile photos. This was done to capture variation in facial morphology. After that, we performed the shape regressions of landmarks' coordinates upon sex and HGS. Results were visualized in forms of thin-plate deformation grids and geometric morphometric morphs.

RESULTS

In both populations, HGS was associated significantly with male facial shape only. In Russian men, strength-related changes of facial shape were almost completely in direction of increase in male-typicality. This was especially evident for the relative lower facial width, which was higher in men compared to women, as well as in stronger men compared to weaker ones. On the contrary, in Tuvans the lower face was relatively narrower in men than in women. However, the facial shape of strong Tuvan men was also associated with relatively wider lower face. Our results indicate that the effect of strength on facial shape is relatively independent of facial sexual dimorphism.

CONCLUSIONS

Our findings clearly demonstrate that physical strength is associated with the shape of the lower part of male faces even in populations with a mismatched direction of lower face sexual dimorphism.

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.

Understanding the Impact of Aging on Attractiveness Using a Machine Learning Model of Facial Age Progression

Background: Advances in machine learning age progression technology offer the unique opportunity to better understand the public's perception on the aging face. Objective: To compare how observers perceive attractiveness and traditional gender traits in faces created with a machine learning model. Methods: Eight surveys were developed, each with 10 sets of photographs that were progressively aged with a machine learning model. Respondents rated attractiveness and masculinity or femininity of each photograph using a sliding scale (range: 0-100). Mean attractiveness scores were calculated and compared between men and women as well as between age groups. Results: A total of 315 respondents (51% men, 49% women) completed the survey. Accuracy of the facial age progression model was 85%. Females were considered significantly less attractive (-10.43, p < 0.01) and less feminine (-7.59, p < 0.01) per decade with the greatest drop over age 40 years. Male attractiveness and masculinity were relatively preserved until age 50 years where attractiveness scores were significantly lower (-5.45, p = 0.39). Conclusions: In this study, observers were found to perceive attractiveness at older ages differently between men and women.

Anthropometric fluctuating asymmetries in living humans through the eyes of an anthropologist

There are many environmental and genetic factors that disrupt the stable structure of development in organisms. Although the strength of these vary, they leave certain signs in the body structure. Fluctuating asymmetry is a widely used population-level index of developmental instability, developmental noise, and robustness. Many bilateral traits are used in fluctuating asymmetry studies in humans. These traits include dermatoglyphics, limb lengths and widths, bilateral facial characters, and teeth. In this review, I evaluate the measurement methods of many bilateral anthropometric characters, taken from the bodies of living individuals with classical digital calipers.

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.

Studying factors influencing facial developmental instability

BACKGROUND

Developmental instability is a component of non-genetic variation that results from random variation in developmental processes. It is considered a sensitive indicator of the physiological state of individuals. It is reflected in various ways, but in this study we focussed on its reflection in fluctuating asymmetry (FA) and morphological integration.

AIM

To assess how, if at all, variations of facial morphology mirror developmental instability across childhood with respect to sex, growth rate and socioeconomic/environmental factors.

SUBJECTS AND METHODS

A set of 210 three-dimensional facial models (of children aged between 6.3 and 14.3 years) originating from the FIDENTIS 3D Face Database was subjected to landmark-based methods of geometric morphometrics to quantify the degree of facial asymmetry and facial morphological integration. In addition, the association with age, sex, and socioeconomic factors was assessed.

RESULTS

Our results showed a nonlinear increase of FA with age up to the age of 14 years. The pattern of sex-related variants in facial FA differed in relation to age, as girls exhibited higher values of FA than boys up to the age of 9 years. We found that a signal of modularity based on functional demands and organisation of the face is of particular importance. Here, girls exhibited higher morphological covariation among modules. During more rapid adolescence-related growth, however, covariation among modules at the asymmetrical level decreased in both sexes.

CONCLUSION

We can conclude that facial morphology was shown to be strongly integrated, particularly until adolescence. This covariation can facilitate an increase of FA. In addition, the results of this study indicate there is a weak association between socioeconomic stress and facial asymmetries. In contrast, sex and growth rate are reflected in developmental instability.

Normality mediates the effect of symmetry on facial attractiveness

Although symmetry, averageness, and sexual dimorphism are usually considered important to facial attractiveness, there are mixed findings regarding whether and how symmetry influences facial attractiveness. The present study introduced "facial normality" to explain the inconsistency of previous research. We hypothesized that symmetry only increased facial attractiveness when it improved facial normality. We manipulated symmetry and normality simultaneously on sixteen Chinese male faces and asked participants to rate the perceived symmetry, perceived normality, and facial attractiveness. The results demonstrated an interactive effect of symmetry and normality on facial attractiveness. The structural equation model results showed two paths from symmetry to facial attractiveness: (1) Symmetry reduced facial attractiveness by decreasing perceived normality; (2) Symmetry increased facial attractiveness by increasing the perceived symmetry and then improving perceived normality. In other words, perceived normality acted as a mediator between symmetry and facial attractiveness. The present study provides a solution to the different effects of symmetry on facial attractiveness in previous studies and suggests that future studies on symmetry and facial attractiveness should consider the mediating role of normality.

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.

Perceived attractiveness of Czech faces across 10 cultures: Associations with sexual shape dimorphism, averageness, fluctuating asymmetry, and eye color

Research on the perception of faces typically assumes that there are some universal values of attractiveness which are shared across individuals and cultures. The perception of attractiveness may, however, vary across cultures due to local differences in both facial morphology and standards of beauty. To examine cross-cultural consensus in the ratings of attractiveness, we presented a set of 120 non-manipulated photographs of Czech faces to ten samples of raters from both European (Czech Republic, Estonia, Sweden, Romania, Turkey, Portugal) and non-European countries (Brazil, India, Cameroon, Namibia). We examined the relative contribution of three facial markers (sexual shape dimorphism, averageness, fluctuating asymmetry) to the perception of attractiveness as well as the possible influence of eye color, which is a locally specific trait. In general, we found that both male and female faces which were closer to the average and more feminine in shape were regarded as more attractive, while fluctuating asymmetry had no effect. Despite a high cross-cultural consensus on attractiveness standards, significant differences in the perception of attractiveness seem to be related to the level of socio-economic development (as measured by the Human Development Index, HDI). Attractiveness ratings by raters from low-HDI countries (India, Cameroon, Namibia) converged less with ratings from Czech Republic than ratings from high-HDI countries (European countries and Brazil). With respect to eye color, some local patterns emerged which we discuss as a consequence of negative frequency-dependent selection.

Change in grip strength in trans people and its association with lean body mass and bone density

OBJECTIVE

Gender-affirming hormonal treatment (HT) in trans people changes physical appearance. Muscle mass and strength are important aspects of physical appearance, but few data exist on the effect of HT on grip strength and muscle mass. This study aimed to investigate the change in grip strength in trans people during the first year of HT and to study the possible determinants of this change and the associations between changes in grip strength, lean body mass and bone mineral density (BMD).

DESIGN AND METHODS

A multicenter, prospective study was performed, including 249 transwomen and 278 transmen. Grip strength, lean body mass and BMD were measured at baseline and after 1 year.

RESULTS

After 1 year of HT, grip strength decreased with -1.8 kg (95% CI -2.6; -1.0) in transwomen and increased with +6.1 kg (95% CI +5.5; +6.7) in transmen. No differences in grip strength change was found between age groups, BMI groups, hormonal administration routes or hormone concentrations. In transmen, increase in grip strength was associated with increase in lean body mass (per kg increase in grip strength: +0.010 kg, 95% CI +0.003; +0.017), while this was not found in transwomen (per kg increase in grip strength: +0.004 kg, 95% CI -0.000; +0.009). Change in grip strength was not associated with change in BMD in transwomen and transmen.

CONCLUSIONS

After 1 year of HT, grip strength decreased in transwomen, and increased in transmen. In transmen only, change in grip strength was associated with change in lean body mass.

Facial masculinity is only weakly correlated with handgrip strength in young adult women

OBJECTIVES

Ancestrally, strength is likely to have played a critical role in determining the ability to obtain and retain resources and the allocation of social status among humans. Responses to facial cues of strength are therefore thought to play an important role in human social interaction. Although many researchers have proposed that sexually dimorphic facial morphology is reliably correlated with physical strength, evidence for this hypothesis is somewhat mixed. Moreover, to date, only one study has investigated the putative relationship between facial masculinity and physical strength in women. Consequently, we tested for correlations between handgrip strength and objective measures of face-shape masculinity.

METHODS

531 women took part in the study. We measured each participant's handgrip strength (dominant hand). Sexual dimorphism of face shape was objectively measured from each face photograph using two methods: discriminant analysis and vector analysis. These methods use shape components derived from principal component analyses of facial landmarks to measure the probability of the face being classified as male (discriminant analysis method) or to locate the face on a female-male continuum (vector analysis method).

RESULTS

Our analyses revealed that handgrip strength is, at best, only weakly correlated with facial masculinity in women. There was a weak significant association between handgrip strength and one measure of women's facial masculinity. The relationship between handgrip strength and our other measure of women's facial masculinity was not significant.

DISCUSSION

Together, these results do not support the hypothesis that face-shape masculinity is an important cue of physical strength, at least in women.

Body symmetry and reproductive hormone levels in women

Fluctuating asymmetry (FA), a morphological marker of developmental stability, may be related to an individual's biological condition, e.g., health or fertility. The aim of this study was to test if the level of a woman's FA was related to her fertility and reproductive potential as measured by reproductive hormone levels. Fifty-three healthy, non-pregnant, naturally cycling women (mean age = 23.42, SD = 1.85 years), participated in the study, conducted in Wrocław (Poland) in May 2015. Early-follicular phase serum levels of anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were measured. FA was calculated based on anthropometric measures of six bilateral body traits, and the composite FA index was used in statistical analyses. No relationship was observed between FA and the levels of FSH, LH, and AMH (p > .05), controlled for potential confounders. However, the level of E2 was positively correlated with FA (p < .05). Thus, in young women, FA was not related to hormones levels related to ovarian reserve, but more symmetrical women had lower E2 levels. As FA is an index of developmental stability, environmental, and genetic stress, the results of the study confirm previous research suggesting that developmental conditions may be related to women's endogenous estrogen levels.

Handgrip Strength as a Darwinian Fitness Indicator in Men

Handgrip strength (HGS) is a robust measure of overall muscular strength and function, and has long been predictive of a multitude of health factors and physical outcomes for both men and women. The fact that HGS represents such a ubiquitous measure of health and vitality may reflect the significance of this trait during human evolution. This trait is also highly sexually dimorphic due to influences of androgenic hormones and fat-free body mass, suggesting that it has been further elaborated through sexual selection. Consistent with this view, research within evolutionary psychology and related fields has documented distinct relationships between HGS and measures of social and sexual behavior, especially in men. Here, we review studies across different societies and cultural contexts showing that male HGS predicts measures of aggression and social dominance, perceived formidability, male-typical body morphology and movement, courtship display, physical attractiveness, and sexual behavior and reproductive fitness. These findings underscore the value of including HGS as an independent measure within studies examining human sexual selection, and corroborate existing research suggesting that specific features of physical strength have and continue to be under positive directional selection in men.

Facial Features: What Women Perceive as Attractive and What Men Consider Attractive

Attractiveness plays an important role in social exchange and in the ability to attract potential mates, especially for women. Several facial traits have been described as reliable indicators of attractiveness in women, but very few studies consider the influence of several measurements simultaneously. In addition, most studies consider just one of two assessments to directly measure attractiveness: either self-evaluation or men's ratings. We explored the relationship between these two estimators of attractiveness and a set of facial traits in a sample of 266 young Spanish women. These traits are: facial fluctuating asymmetry, facial averageness, facial sexual dimorphism, and facial maturity. We made use of the advantage of having recently developed methodologies that enabled us to measure these variables in real faces. We also controlled for three other widely used variables: age, body mass index and waist-to-hip ratio. The inclusion of many different variables allowed us to detect any possible interaction between the features described that could affect attractiveness perception. Our results show that facial fluctuating asymmetry is related both to self-perceived and male-rated attractiveness. Other facial traits are related only to one direct attractiveness measurement: facial averageness and facial maturity only affect men's ratings. Unmodified faces are closer to natural stimuli than are manipulated photographs, and therefore our results support the importance of employing unmodified faces to analyse the factors affecting attractiveness. We also discuss the relatively low equivalence between self-perceived and male-rated attractiveness and how various anthropometric traits are relevant to them in different ways. Finally, we highlight the need to perform integrated-variable studies to fully understand female attractiveness.