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Symmetry was calculated by taking left and right deviation from the midline, calculated from inter-pupillary distance, for points D1-D6 and then summing the absolute value of individual scores. Sexual dimorphism was measured by measuring distance between specific points and calculating four ratios based on these distances: Cheekbone Prominence (ChP, D3/D6), Jaw Height/Lower Face Height (JH/LFH, D9/D8), Lower Face Height/Face Height (LFH/FH, D8/D7), and Face Width/Lower Face Height (FW/LFH, D3/D8). All images were normalised on inter-pupillary distance.
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Many animals both display and assess multiple signals. Two prominently studied traits are symmetry and sexual dimorphism, which, for many animals, are proposed cues to heritable fitness benefits. These traits are associated with other potential benefits, such as fertility. In humans, the face has been extensively studied in terms of attractiveness....
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Citations
... This approach may not be ideal, however, since there is some evidence for interrelationships among symmetry, prototypicality, and sexual dimorphism. For example, several studies have reported that more masculine male and more feminine female faces tend to be more symmetric (Gangestad & Thornhill, 2003;Little et al., 2008; but see also Van Dongen et al., 2020) and other work has demonstrated that faces with more distinctive (i.e., the converse of prototypical) face shapes tend to be more asymmetric Lee et al., 2016). Such results suggest that it may be useful to compare findings for health ratings and symmetry, prototypicality, and sexual dimorphism when these physical characteristics are analysed individually and when these physical characteristics are entered simultaneously as predictors of health ratings. ...
... Some researchers have previously reported that facial symmetry and sexual dimorphism are positively correlated and suggested that this correlation occurs because both characteristics reflect a common underlying quality (i.e., good physical health or immune function, Gangestad & Thornhill, 2003;Little et al., 2008). By contrast with these findings, facial symmetry and sexual dimorphism were not significantly correlated in our study (see also Van Dongen et al., 2020). ...
Health perceptions are thought to play an important role in human mate preferences. Although many studies have investigated potential relationships between health ratings of faces and facial symmetry, prototypicality, and sexual dimorphism, findings have been mixed across studies. Consequently, we tested for potential relationships between health ratings of faces and the symmetry, prototypicality, and sexual dimorphism of those faces’ shapes. When these three shape characteristics were considered in separate regression models, we observed significant positive relationships between health ratings and both shape symmetry and prototypicality. By contrast, health ratings and sexual dimorphism were not significantly correlated in these analyses. However, in analyses in which symmetry, prototypicality, and sexual dimorphism were entered simultaneously as predictors in a single model, prototypicality, but not symmetry, was significantly correlated with health ratings. Moreover, sexual dimorphism predicted health ratings of female, but not male, faces in these analyses. Collectively, these results suggest that the relationship between symmetry and health ratings is, at least partly, driven by the effect of prototypicality on health perceptions and highlight the importance of considering multiple aspects of face shape when investigating factors that predict perceived health.
... Consistent with such theorizing, among rhesus macaques, symmetry is positively associated with greater sexual dimorphism and health (Little et al., 2008(Little et al., , 2012 and is preferred by opposite-sex conspeci cs (Waitt & Little, 2006). ...
Evolutionary social science is having a renaissance. This volume showcases the empirical and theoretical advancements produced by the evolutionary study of romantic relationships. The editors assembled an international collection of contributors to trace how evolved psychological mechanisms shape strategic computation and behavior across the life span of a romantic partnership. Each chapter provides an overview of historic and contemporary research on the psychological mechanisms and processes underlying the initiation, maintenance, and dissolution of romantic relationships. Contributors discuss popular and cutting-edge methods for data analysis and theory development, critically analyze the state of evolutionary relationship science, and provide discerning recommendations for future research. The handbook integrates a broad range of topics (e.g., partner preference and selection, competition and conflict, jealousy and mate guarding, parenting, partner loss and divorce, and post-relationship affiliation) that are discussed alongside major sources of strategic variation in mating behavior, such as sex and gender diversity, developmental life history, neuroendocrine processes, technological advancement, and culture. Its content promises to enrich students’ and established researchers’ views on the current state of the discipline and should challenge a diverse cross-section of relationship scholars and clinicians to incorporate evolutionary theorizing into their professional work.
... Samal A et al, and Little AC et al conducted study on morphometric analysis of facial features i.e. head, eyes, orbits, nose, lips, and mouth, and ears which showed statistical difference between adult males and females. This is in concurrence with our study that found the same [7,8]. ...
Background: Cheiloscopy is the study of lip prints. This field has proven that lip prints are unique to individuals and can be used as a tool for identification. However, lip morphology as an identifier needs to be probed further. Aim: The present study was formulated with an opinion to understand whether lip sizes can be used as gender identifiers. Methodology: The study involved a pool of 30 subjects who were equal in gender distribution. The sample was subjected to collection of lip prints and resulting data was analyzed in consultation with institutional statistician. Observations: The results showed that lip sizes showed a definitive variance between males and females in a manner which was statistically significant. Conclusion: The study concluded that in a comparative role, lip prints can be used to identify males and females but a larger study is needed to confirm the hypothesis.
... ese secondary characteristics make people appear more masculine or feminine. Many studies provide evidence that masculinity and femininity provide more depth to a person's beauty than symmetry [10,17,18]. Intrinsic features of the face, such as facial texture and skin color, can also affect the perception of beauty. ...
The beauty industry has seen rapid growth in multiple countries and due to its applications in entertainment, the analysis and assessment of facial attractiveness have received attention from scientists, physicians, and artists because of digital media, plastic surgery, and cosmetics. An analysis of techniques is used in the assessment of facial beauty that considers facial ratios and facial qualities as elements to predict facial beauty. Here, the facial landmarks are extracted to calculate facial ratios according to Golden Ratios and Symmetry Ratios, and an ablation study is performed to find the best performing feature set from extracted ratios. Subsequently, Gray Level Covariance Matrix (GLCM), Hu's Moments, and Color Histograms in the HSV space are extracted as texture, shape, and color features, respectively. Another ablation study is performed to find out which feature performs the best when concatenated with the facial landmarks. Experimental results show that the concatenation of primary facial characteristics with facial landmarks improved the prediction score of facial beauty. Four models are trained, K-Nearest Neighbors (KNN), Linear Regression (LR), Random Forest (RF), and Artificial Neural Network (ANN) on a dataset of 5500 frontal facial images, and amongst them, KNN performs the best for the concatenated features achieving a Pearson's Correlation Coefficient of 0.7836 and a Mean Squared Error of 0.0963. Our analysis also provides us with insights into how different machine learning models can understand the concept of facial beauty.
... We observe that conditioning by race yields slightly different conclusions than conditioning by sex. Whereas the set of facial features and skin tones used to predict the race of an individual can overlap, there is sexual dimorphism apparent in the labeling of human faces [51][52][53]. For example, we observe, on average, faces labeled as White, Middle Eastern, Latino, and Asian tend to have lighter skin, whereas Black and Indian tend to have darker skin tones. ...
The proliferation of automated facial recognition in various commercial and government sectors has caused significant privacy concerns for individuals. A recent and popular approach to address these privacy concerns is to employ evasion attacks against the metric embedding networks powering facial recognition systems. Face obfuscation systems generate imperceptible perturbations, when added to an image, cause the facial recognition system to misidentify the user. The key to these approaches is the generation of perturbations using a pre-trained metric embedding network followed by their application to an online system, whose model might be proprietary. This dependence of face obfuscation on metric embedding networks, which are known to be unfair in the context of facial recognition, surfaces the question of demographic fairness -- \textit{are there demographic disparities in the performance of face obfuscation systems?} To address this question, we perform an analytical and empirical exploration of the performance of recent face obfuscation systems that rely on deep embedding networks. We find that metric embedding networks are demographically aware; they cluster faces in the embedding space based on their demographic attributes. We observe that this effect carries through to the face obfuscation systems: faces belonging to minority groups incur reduced utility compared to those from majority groups. For example, the disparity in average obfuscation success rate on the online Face++ API can reach up to 20 percentage points. Further, for some demographic groups, the average perturbation size increases by up to 17\% when choosing a target identity belonging to a different demographic group versus the same demographic group. Finally, we present a simple analytical model to provide insights into these phenomena.
... Testosterone is believed to have a greater impact on immune function than estrogen, making sexually dimorphic features more costly for men in the ICHH context [34]. Therefore, if we assume that FA and masculinity both index underlying genetic quality, we expect a stronger correlation between FA and masculinity in men. ...
Background:
Fluctuating asymmetry is often used as an indicator of developmental instability, and is proposed as a signal of genetic quality. The display of prominent masculine phenotypic features, which are a direct result of high androgen levels, is also believed to be a sign of genetic quality, as these hormones may act as immunosuppressants. Fluctuating asymmetry and masculinity are therefore expected to covary. However, there is lack of strong evidence in the literature regarding this hypothesis.
Materials and methods:
In this study, we examined a large dataset of high-density 3D facial scans of 1260 adults (630 males and 630 females). We mapped a high-density 3D facial mask onto the facial scans in order to obtain a high number of quasi-landmarks on the faces. Multi-dimensional measures of fluctuating asymmetry were extracted from the landmarks using Principal Component Analysis, and masculinity/femininity scores were obtained for each face using Partial Least Squares. The possible correlation between these two qualities was then examined using Pearson's coefficient and Canonical Correlation Analysis.
Results:
We found no correlation between fluctuating asymmetry and masculinity in men. However, a weak but significant correlation was found between average fluctuating asymmetry and masculinity in women, in which feminine faces had higher levels of fluctuating asymmetry on average. This correlation could possibly point to genetic quality as an underlying mechanism for both asymmetry and masculinity; however, it might also be driven by other fitness or life history traits, such as fertility.
Conclusions:
Our results question the idea that fluctuating asymmetry and masculinity should be (more strongly) correlated in men, which is in line with the recent literature. Future studies should possibly focus more on the evolutionary relevance of the observed correlation in women.
... But, e.g., investigations in Reference [14] show that females of the rock lizard Lacerta monticola prefer more symmetrical males as potential mates, by which the bilateral symmetry is preserved. The sexual preference among Humans shows, correspondingly, that a high degree of symmetry in the human faces is attractive, and it is found to be masculine for men and to be feminine for females [15]; bilateral symmetry is, in general, aesthetically attractive [16]. ...
Most biological organisms exhibit different kinds of symmetry; an Animal (Metazoa), which is our Darwinist ancestor, has bilateral symmetry, and many plants exhibit rotational symmetry. It raises some questions: I. How can the evolution from an undifferentiated cell without bilateral symmetry to a complex biological organism with symmetry, which is based on asymmetric DNA and enzymes, lead to the bilateral symmetry? II. Is this evolution to an organism with bilateral symmetry obtained by other factors than DNA and enzymatic reactions? The existing literature about the evolution of the bilateral symmetry has been reviewed, and a new hypothesis has been formulated based on these reviews. The hypothesis is that the morphogenesis of biosystems is connected with the metabolism and that the oscillating kinetics in the Glycolysis have played a role in the polarity of the biological cells and in the establishment of the bilateral symmetry in Animals.
... The degree of sexual dimorphism in fWHR varies across populations, and in some cases significant differences are not observed [20,28,31,38,39]. However, despite the facts that generally sex differences in fWHR are weak, in overwhelming number of populations men have slightly higher values of this facial parameter than women (meta-analytic study involving data on 32 populations [32]), which is especially pronounced in Asians [27]. From this perspective, Buryats are of a special research interest, since according to recent findings, they demonstrate inversed sexual dimorphism in fWHR [41,42]. ...
... In addition to the assessment of the full facial shape, differences in partial morphological facial parameters were analyzed (Tab. 1) [2,32,45], which allowed localization of the differences according to specific facial areas. ...
The aim of the present experimental study was to investigate possible associations between indi - vidual cooperativeness and facial morphology. Participants of the study were Buryats of Southern Si - beria (males: N=98; females: N=89; mean age 20 ± 2y.). Individual cooperativeness was assessed in experimental economic game “Public Goods Game”, which was conducted “face-to-face”, in groups of 4 same-sex individuals, who were strangers to each other. The game involved real monetary pay-offs. In the course of the experiment such individual behavioral features as propensity for unconditional/conditional cooperation, selfishness, or free-riding were revealed. Facial shapes of participants were explored through anthropological photographs using geometric morphometrics, and via assessing standard facial indexes. As a result the relationship between facial shape and unconditional cooperation was identified and visualized. This relationship appeared only among males. The analysis of sex-specific facial traits of Buryats revealed that faces of male unconditional cooperators combined both male-specific, and female-specific facial features. This is the first study to investigate association between full facial shape and human cooperativeness.
... In the photographs, individuals posed with a neutral expression under standardised lighting conditions. For macaque monkey images, neutral front-on images were extracted from video recordings with variable lighting conditions see [45]. Human and monkey images were aligned on inter-pupillary distance to equate size. ...
Background: Visual symmetry is often found attractive. Symmetry may be preferred either due to a bias in the visual system or due to evolutionary selection pressures related to partner preference. Simple perceptual bias views predict that symmetry preferences should be similar across types of stimuli and unlikely to be related to factors such as age. Methods: The current study examined preferences for symmetry across age groups (pre-puberty vs post-puberty) and stimuli type (human face vs monkey face). Pairs of images manipulated for symmetry were presented and participants asked to choose the image they preferred. Participants repeated the task and were asked to detect symmetry. Results: Both age of observer and stimuli type were associated with symmetry preferences. Older observers had higher preferences for symmetry but preferred it most in human vs monkey stimuli. Across both age groups, symmetry preferences and detection abilities were weakly related. Conclusions: The study supports some ideas from an evolutionary advantage view of symmetry preference, whereby symmetry is expected be higher for potential partners (here human faces) and higher post-puberty when partner choice becomes more relevant. Such potentially motivational based preferences challenge perceptual bias explanations as a sole explanation for symmetry preferences but may occur alongside them.
...  ðàáîòå A. Ëèòòëà ñ ñîàâòîðàìè [Little et al., 2008] ðàçðàáîòàíà ìåòîäèêà îöåíêè ðàçìåðíûõ õàðàêòåðèñòèê ëèöà, ïîêàçûâàþùèõ ñòåïåíü ìàñêóëèííîñòè.  êà÷åñòâå òàêèõ õàðàêòåðèñòèê èñïîëüçîâàíî ñîîòíîøåíèå ñêóëîâîãî è íèaeíå÷åëþñòíîãî äèàìåòðîâ, à òàêaeå ïðèçíàêè ìàññèâíîñòè íèaeíåãî ýòàaeà ëèöà (îò ëèíèè ñìûêàíèÿ ãóá äî íèaeíåé òî÷êè ïîäáîðîäêà). ...
Introduction. The aim of the work is to search for possible associations between facial masculinity and 2D:4D ratio. It is supposed that sex steroids moderate the facial shape sexual differences. On the other hand digit ratio (2D:4D) is a proxy to prenatal testosterone. So suggests that there is a relationship between these two systems.
Material and methods. A sample of 203 individuals belonging to two geographical groups of Russians (99 males and 104 females) was studied. The age of the surveyed individuals is from 18 to 24 years. The lengths of the second and fourth fingers on the left and right hand are measured as well as the main dimensions of the face (in the photos). Correlation, regression and canonical analyses are used to find connections of 2D:4D ratio and face shape. The sexual differences and dissimilarity between two geographical samples were studied by discriminant analysis.
Results. The value of sexual dimorphism based on facial features was estimated by using Mahalanobis distances in each of the two geographical groups. The Moscow sample has more noticeable sexual differences of facial shape than the Gorno-Altaysk one. The characteristics that separate males and females in both regional groups are height of the face and signs of massiveness of the chin. None of the types of intragroup analysis detect correlations between facial masculinity and the 2D:4D ratio. Low associations were found by analysis of group’s means of 2D:4D ratio and chin’s height.
Discussion. It is possible that the significance of sexual differences in the 2D:4D index is greatly exaggerated. So, that suggests that prenatal and pubertal testosterone have differential effects on facial shape.
Conclusion. These relationships of the digit ratio and face shape are revealing only at the intergroup level and only as trends. In addition the territorial variability of these two morphological complexes overlaps and thus cut down the sexual differences.
