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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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... Additionally, subdividing 3D models into smaller sections based on specific landmark sets [61] could provide more granular insights into asymmetry indices. Future research will expand the sample to encompass a broader age range, including a more stratified representation across gender groups [62], given that facial asymmetries are more prevalent among older individuals and cisgender males. Furthermore, focusing on specific facial regions that are particularly prone to asymmetry and biometric analyses is a challenge that will allow us to evaluate the accuracy and reliability of the proposed methodology in these targeted patients. ...
Facial asymmetry presents a significant challenge for health practitioners, including physicians, dentists, and physical therapists. Manual measurements often lack the precision needed for accurate assessments, highlighting the appeal of imaging technologies like structured light scanners and photogrammetric systems. However, high-end commercial systems remain cost prohibitive, especially for public health services in developing countries. This study aims to evaluate cell-phone-based photogrammetric methods for generating 3D facial models to detect facial asymmetries. For this purpose, 15 patients had their faces scanned with the ACADEMIA 50 3D scanner, as well as with cell phone images and videos using photogrammetry and videogrammetry, resulting in 3D facial models. Each 3D model (coming from a 3D scanner, photogrammetry, and videogrammetry) was half-mirrored to analyze dissimilarities between the two ideally symmetric face sides using Hausdorff distances between the two half-meshes. These distances were statistically analyzed through various measures and hypothesis tests. The results indicate that, in most cases, both photogrammetric and videogrammetric approaches are as reliable as 3D scanning for detecting facial asymmetries. The benefits and limitations of using images, videos, and 3D scanning are also presented.
... This approach may be somewhat limited because it is not instructive about which of these face-shape characteristics independently predict attractiveness. Indeed, some studies have reported that averageness and symmetry 22,25 and symmetry and sexual dimorphism are positively correlated in face images 23,[26][27][28] . ...
Facial attractiveness influences important social outcomes and most studies investigating possible predictors of facial attractiveness have tested for effects of shape symmetry, averageness (i.e., the converse of distinctiveness), and sexual dimorphism (i.e., masculinity–femininity). These studies have typically either tested for these possible effects by experimentally manipulating shape characteristics in faces images or have tested only for bivariate correlations between shape characteristics and attractiveness judgments. However, these two approaches have been criticised for lacking ecological validity and providing little insight into the independent contributions of symmetry, averageness, and sexual dimorphism, respectively. Moreover, the few studies that have investigated the independent contributions of symmetry, averageness, and sexual dimorphism have reported mixed results. Here we measured shape symmetry, averageness, and sexual dimorphism from face images and assessed their independent contribution to attractiveness ratings. Linear mixed effects models showed that facial attractiveness was significantly predicted by averageness in male and female faces and femininity in female faces, but not by masculinity in male faces or symmetry. These results are consistent with other recent work suggesting that averageness and femininity, rather than symmetry and masculinity, predict facial attractiveness.
... Faces represent a socially relevant class of stimuli that have been a major topic in perception research [11]. People regularly and frequently extract important social information from faces, including perceptions of age, gender, health, and emotion [10,12,16,23]. Past work has shown that people are particularly sensitive to processing the color appearance of human faces [7,26,27], and that even small changes to facial color appearance can impact how other people evaluate them [1,25,28]. ...
... Pour maximiser les chances de survie de sa progéniture (et de ses gènes), les femelles sélectionneront par conséquent les individus offrant le train doté de la plus belle taille, couleur et symétrie. Chez l'espèce humaine, l'attirance sexuelle envers les individus présentant la meilleure symétrie faciale pourrait inconsciemment découler d'un mécanisme similaire (Little et al. 2008). ...
En biologie évolutive, l'approche fonctionnelle vise à comprendre comment des traits, qu'ils soient morphologiques ou comportementaux, évoluent pour s’ajuster aux exigences environnementales, afin d’optimiser la survie et la reproduction d'un organisme. L’écologie comportementale humaine propose d’utiliser cette approche pour appréhender les comportements de subsistance des chasseurs-cueilleurs actuels et passés. Les archéozoologues ont examiné plus spécifiquement les prédictions des modèles économétriques issus de la théorie de l’approvisionnement optimal (optimal foraging theory) pour appréhender les décisions et les stratégies liées à l’alimentation et plus globalement à l’économie de la matière première alimentaire. Bien que la dimension évolutionniste de cette démarche ait séduit plusieurs générations d’archéozoologues en Amérique du Nord, elle peine à obtenir une reconnaissance académique en Europe. Elle y est souvent perçue comme une approche réductrice et déshumanisante en raison de l’accent qu’elle met sur des données quantifiables et économiques des comportements de prédation, au détriment de dimensions plus sociales et culturelles. Ce jugement idéologique occulte malheureusement la puissance heuristique des modèles d’optimisations pour l’archéologie et j’ai souhaité, à travers ce manuscrit, démystifier et clarifier cette approche en déconstruisant avec pédagogie ses soubassements conceptuels et méthodologiques. Cet objectif m’a conduit à remonter l’histoire des grands piliers conceptuels de l’écologie comportementale pour mettre en évidence les spécificités de cette discipline vis-à-vis des autres sciences du comportement, actuelles et passées, en particulier l’éthologie et la sociobiologie. Par la suite, je me suis penché sur l’écologie comportementale humaine en examinant son évolution, les controverses qu’elle a suscitées aux États-Unis et en France, ainsi que la réception de cette discipline par l'archéologie. Les deux derniers chapitres se focalisent sur le principal modèle de l’optimal foraging theory utilisé en archéozoologie : le modèle de la sélection optimale des proies (prey choice model). Après avoir examiné en détail les concepts et le fonctionnement de ce modèle, je m’attarde sur la manière de l’opérationnaliser en archéologie et sur les limites méthodologiques associées à son application. Je termine par une mise en perspective de ses résultats, en mettant l'accent sur les variations de l'efficacité du foraging.
... 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.
... The research continued with evidence of additional factors -asymmetry in men is significantly linked to lifelong health handicaps (Møller, 1990) or lower fertility (Manning et al., 1998). Furthermore, the symmetry of organisms correlates with growth rate and survivability (Livshits & Kobyliansky, 1984;Little et al., 2008), potential fertility (Jasienska et al., 2006) as well as real and age-independent fecundity (Møller et al., 1995) in women. The importance of symmetry in ensuring health has also been proven by other studies. ...
Symmetry belongs to one of the basic principles of the beauty of human and non-human objects since antiquity. Even though its significance has been verified by numerous theories and research studies, there is a number of papers suggesting that this principle may be false. The study identifies five major evolutionary principles, in the context of new approaches and research ambiguities based mainly on neuroscience and evolutionary psychology, that support the thesis that highlights the significance of symmetry in the perception and assessment of attractiveness: 1. symmetry as an honest signal of various health characteristics; 2. symmetry as proof of developmental stability; 3. effectiveness; 4. comprehensibility; 5. predictability. In the context of the mechanisms described above it also seeks possible explanations for the existence of contradictory research results related to the attractiveness of symmetry. The outcome of the study is the postulation of three hypotheses: 1. the naturalness hypothesis (symmetry is only attractive to the same degree that it naturally occurs in the subject); 2. the accent hypothesis (minor asymmetries do not disprove the principles of symmetry, they make them more visible); 3. the ecology hypothesis (the attractiveness of symmetry is conditioned by the situation and depends on the type of subject assessed) that allow us to integrate both past and contemporary (and putatively contradictory) research findings. The paper also provides proposals for the verification of the postulated hypotheses.
... 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.
