Asymmetry and Symmetry in the Beauty of Human Faces

From Filters to Scalpels-Understanding Perceptions of Facial Asymmetry: An AAFPRS Survey

Facial asymmetries can significantly affect patient satisfaction post-surgery. Social media can impact a patient's perception of their asymmetries. To gather insights into the practices, perceptions, and approaches concerning facial asymmetry among facial plastic surgeons. The aim of this study was to understand the impact of social media on perceptions of facial asymmetry. This is an American Academy of Facial Plastic and Reconstructive Surgeons (AAFPRS) survey consisting of 46 questions that sought to understand facial plastic surgeons' perceptions of facial asymmetry, their consultation process, their patients' perspectives on their own facial asymmetries, and patient satisfaction. The survey was distributed to 1,269 members of AAFPRS across community hospitals, private practices, and academic hospitals. Sixty-seven members completed the survey. The survey revealed that 31% (21) of surgeons face challenges in managing patient expectations regarding facial asymmetry. In addition, 12% (8) of surgeons felt that patients did not initially recognize their own asymmetries. Eighty-seven percent (58) of surgeons emphasize the natural occurrence of asymmetry during consultations to set realistic expectations. This study emphasizes the need for thorough patient education during initial consultations to align expectations with achievable outcomes. Surgeons should explain the natural occurrence of asymmetry clearly and use digital imaging to show patients realistic previews of surgical results.

Two- and three-dimensional symmetry of maxillary incisors: A clinical study

OBJECTIVE

To assess the 2D and 3D natural symmetry of the maxillary incisors.

MATERIALS AND METHODS

Maxillary alginate impressions were taken of 59 young adult volunteers. Gender, orthodontic treatment history, and dominant hand were collected. For 2D analysis, a digital caliper was used for measurements on maxillary casts. For 3D analysis, the casts were scanned using a lab scanner, and the labial surface symmetry of contralateral incisors was evaluated. Mann-Whitney tests and Student's t-test were performed, α = 0.05.

RESULTS

Results indicated a lack of identical lengths among contralateral central or lateral incisors, with minimal occurrences of identical width measurements. 68% of central incisors and 73% of lateral incisors showed differences in length exceeding 0.2 mm. Central incisors showed more similarities than lateral incisors in width, with 61% central incisors and 47% lateral incisors having differences under 0.2 mm. The differences between highly asymmetrical contralateral teeth are situated at the transitional lines. The influence of sexual dimorphism, orthodontic factors, and the dominant hand on incisors' symmetry was not statistically significant.

CONCLUSIONS

2D and 3D symmetry of the natural maxillary incisors are rare. 3D symmetry remains consistent across orthodontic treatment status, gender, and dominant hand, suggesting its independence from such parameters.

CLINICAL SIGNIFICANCE

To achieve a natural and aesthetic smile rehabilitation, the symmetry of the maxillary incisors must be well understood. In our study, 2D and 3D symmetry of the maxillary incisors occurred rarely, but central incisors showed more similarities than lateral incisors in width, with differences under 0.2 mm. On the other hand, differences between highly asymmetrical contralateral teeth are situated at the transitional lines. These conclusions should be included in further computer-assisted three-dimensional smile designs.

Subjective and Objective Evaluation of the Symmetry of Maxillary Incisors among Residents of Southwest Poland

Dental aesthetics is an essential factor affecting people’s psychosocial wellbeing. One of the most critical components of an aesthetic smile is symmetry within the dentition. Dentists and orthodontists, unlike laypersons, are critical in assessing dental aesthetics. This study aimed to evaluate the accuracy of patients’ assessment of the symmetry of their maxillary incisors and some factors that influence it. The study was conducted on 83 participants aged from 11 to 39 years. First, the participants filled out a questionnaire to obtain patients’ opinions of the symmetry of their upper incisors. This stage was followed by an intraoral examination, during which we used a digital caliper to measure the width of four maxillary incisors. The data were entered into STATISTICA v. 13.3. The following conclusions were drawn from the study. First, the respondents were generally able to determine the asymmetry of the incisors. Second, among the maxillary incisors, the participants defined the symmetry of maxillary central incisors more accurately than the maxillary lateral incisors. The cut-off value for incisor asymmetry noticeable to a layperson is 0.2 mm for maxillary medial incisors and 0.55 for maxillary lateral incisors. Third, we found no dependence of the accuracy of the assessment of incisor asymmetry on the age of the subjects; however, in our study group, the age range (spread) was not significant, so further studies are recommended. Finally, results concerning the relationship with gender showed that males assess the level of symmetry of their maxillary incisors more accurately than females.

The Gospel’s Double Antisymmetry as the End-Point of the Development of Western Society

In this article, we addressed the question of whether the Gospel’s double antisymmetry can be found in reality as such and especially in Western society, which has obviously made developments in its history. Based on the conceptual analysis of language, we came to the conclusion that there are four layers of reality: the material world, lifeworld, material life and personal life. Through the analysis of individual layers of reality, we have come to the realization that they are characterized by the double antisymmetry (horizontal and vertical) spoken of in the Gospel. While the world (material and lived) is characterized by the primacy of parts over the whole, life (material and personal) is characterized by the primacy of the whole over the parts. Furthermore, if the material world and material life are characterized by the supremacy of the abstract over the concrete, the lifeworld and personal life are characterized by the supremacy of the concrete over the abstract. Based on examples from logic, science, and society, we also show how this antisymmetry manifests itself in concrete phenomena of everyday life and how it points to the gradual conversion of Western society, which is, according to our conclusion, becoming more and more like the People of God, the heir of the Kingdom of Heaven proclaimed by Jesus of Nazareth.

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.

Accuracy of Mobile Device-Compatible 3D Scanners for Facial Digitization: Systematic Review and Meta-Analysis

Background

The accurate assessment and acquisition of facial anatomical information significantly contributes to enhancing the reliability of treatments in dental and medical fields, and has applications in fields such as craniomaxillofacial surgery, orthodontics, prosthodontics, orthopedics, and forensic medicine. Mobile device–compatible 3D facial scanners have been reported to be an effective tool for clinical use, but the accuracy of digital facial impressions obtained with the scanners has not been explored.

Objective

We aimed to review comparisons of the accuracy of mobile device–compatible face scanners for facial digitization with that of systems for professional 3D facial scanning.

Methods

Individual search strategies were employed in PubMed (MEDLINE), Scopus, Science Direct, and Cochrane Library databases to search for articles published up to May 27, 2020. Peer-reviewed journal articles evaluating the accuracy of 3D facial models generated by mobile device–compatible face scanners were included. Cohen d effect size estimates and confidence intervals of standardized mean difference (SMD) data sets were used for meta-analysis.

Results

By automatic database searching, 3942 articles were identified, of which 11 articles were considered eligible for narrative review, with 6 studies included in the meta-analysis. Overall, the accuracy of face models obtained using mobile device–compatible face scanners was significantly lower than that of face models obtained using professional 3D facial scanners (SMD 3.96 mm, 95% CI 2.81-5.10 mm; z=6.78; P<.001). The difference between face scanning when performed on inanimate facial models was significantly higher (SMD 10.53 mm, 95% CI 6.29-14.77 mm) than that when performed on living participants (SMD 2.58 mm, 95% CI 1.70-3.47 mm, P<.001, df=12.94).

Conclusions

Overall, mobile device–compatible face scanners did not perform as well as professional scanning systems in 3D facial acquisition, but the deviations were within the clinically acceptable range of <1.5 mm. Significant differences between results when 3D facial scans were performed on inanimate facial objects and when performed on the faces of living participants were found; thus, caution should be exercised when interpreting results from studies conducted on inanimate objects.

The Role of Symmetry in the Aesthetics of Residential Building Façades Using Cognitive Science Methods

Symmetry is an important visual feature for humans and its application in architecture is completely evident. This paper aims to investigate the role of symmetry in the aesthetics judgment of residential building façades and study the pattern of eye movement based on the expertise of subjects in architecture. In order to implement this in the present paper, we have created images in two categories: symmetrical and asymmetrical façade images. The experiment design allows us to investigate the preference of subjects and their reaction time to decide about presented images as well as record their eye movements. It was inferred that the aesthetic experience of a building façade is influenced by the expertise of the subjects. There is a significant difference between experts and non-experts in all conditions, and symmetrical façades are in line with the taste of non-expert subjects. Moreover, the patterns of fixational eye movements indicate that the horizontal or vertical symmetry (mirror symmetry) has a profound influence on the observer’s attention, but there is a difference in the points watched and their fixation duration. Thus, although symmetry may attract the same attention during eye movements on façade images, it does not necessarily lead to the same preference between the expert and non-expert groups.

What Experts Appreciate in Patterns: Art Expertise Modulates Preference for Asymmetric and Face-Like Patterns

This study set out to investigate whether and how aesthetic evaluations of different types of symmetric, as well as abstract vs. representational patterns are modulated by art expertise. To this end, we utilized abstract asymmetric, symmetric, and “broken” patterns slightly deviating from symmetry, as well as more representational patterns resembling faces (also symmetric or broken). While it has already been shown that symmetry preference decreases with art expertise, it was still unclear whether an already established relationship between art expertise and preference for abstract over representational art can be similarly found as a preference for abstract over representational patterns, as these are non-art objects. Nevertheless, we found profound differences in aesthetic preferences between art experts and laypersons. While art experts rated asymmetric patterns higher than laypersons, as expected, they rated face-like patterns lower than laypersons. Also, laypersons rated all other types of patterns higher than asymmetric patterns, while art experts rated the other patterns similar or lower than asymmetric patterns. We found this both for liking and for interest ratings. As no differences between art experts and laypersons were found regarding memory recognition of new and old patterns, this effect is not likely due to differences in memory performance. In sum, this study further extends our knowledge about the influence of art expertise on aesthetic appreciation.

Symmetry preference in shapes, faces, flowers and landscapes

Most people like symmetry, and symmetry has been extensively used in visual art and architecture. In this study, we compared preference for images of abstract and familiar objects in the original format or when containing perfect bilateral symmetry. We created pairs of images for different categories: male faces, female faces, polygons, smoothed version of the polygons, flowers, and landscapes. This design allows us to compare symmetry preference in different domains. Each observer saw all categories randomly interleaved but saw only one of the two images in a pair. After recording preference, we recorded a rating of how salient the symmetry was for each image, and measured how quickly observers could decide which of the two images in a pair was symmetrical. Results reveal a general preference for symmetry in the case of shapes and faces. For landscapes, natural (no perfect symmetry) images were preferred. Correlations with judgments of saliency were present but generally low, and for landscapes the salience of symmetry was negatively related to preference. However, even within the category where symmetry was not liked (landscapes), the separate analysis of original and modified stimuli showed an interesting pattern: Salience of symmetry was correlated positively (artificial) or negatively (original) with preference, suggesting different effects of symmetry within the same class of stimuli based on context and categorization.

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.

Influence of physiological stress on the presence of hypoplasia and fluctuating asymmetry in a medieval population from the village of Sypniewo

This study aims to estimate the levels of physiological stress in the medieval rural population of Sypniewo by evaluating patterns of fluctuating asymmetry (FA) and enamel hypoplasia (EH), and provide information on the influence of physiological stress during the prenatal and perinatal period on early childhood development. Stress is defined as any external or internal condition that challenges homeostasis of an organism. FA is associated with physiological stress occurring mainly during prenatal development and early childhood. The level of FA is thought to reflect the intensity of the stressor(s). EH is caused by physiological stress such as nutritional instability during the first years of life. The studied material consisted of 126 skulls from the village of Sypniewo (Poland). Cranial radiographs were taken in postero-anterior (P-A) and basal views. The images were scanned and calibrated. Measurements of the cranium were used to estimate FA. The presence of EH was assessed using standard anthropological methods The highest levels of FA were observed in the region of the cranial base. EH was observed in 29% of individuals from the rural skeletal series. There was no statistically significant correlation between FA and EH occurrence or between sex and the studied stress indicators.

Dynamic properties of successful smiles

Facial expression of emotion is a foundational aspect of social interaction and nonverbal communication. In this study, we use a computer-animated 3D facial tool to investigate how dynamic properties of a smile are perceived. We created smile animations where we systematically manipulated the smile’s angle, extent, dental show, and dynamic symmetry. Then we asked a diverse sample of 802 participants to rate the smiles in terms of their effectiveness, genuineness, pleasantness, and perceived emotional intent. We define a “successful smile” as one that is rated effective, genuine, and pleasant in the colloquial sense of these words. We found that a successful smile can be expressed via a variety of different spatiotemporal trajectories, involving an intricate balance of mouth angle, smile extent, and dental show combined with dynamic symmetry. These findings have broad applications in a variety of areas, such as facial reanimation surgery, rehabilitation, computer graphics, and psychology.

The relationship between facial shape asymmetry and attractiveness in Mexican students

OBJECTIVES

It has been postulated that symmetric faces are considered more attractive than asymmetric ones because symmetry may signal high quality due to developmental stability. However, other studies showed that both symmetric and slightly asymmetric faces are considered attractive. Here we aim to explore this discrepancy, beginning with the analysis of the normal prevalence of facial symmetry in a population as a necessary first step prior to any attractiveness assessment.

METHODS

We collected facial landmarks from two-dimensional digital images of a sample of Mexican individuals (280 females and 285 males aged 18-68 years) that were analyzed using geometric morphometric methods. Then, we chose a subsample of 100 photographs (50 females and 50 males aged 18-27 years) selected to represent a broad range of asymmetrical variation, in order to evaluate attractiveness using a sex-opposite test. Finally, we analyzed the linear correlation between attractiveness and asymmetry.

RESULTS

We found that every evaluated subject presents some degree of facial asymmetry, and that both fluctuating asymmetry and directional asymmetry were significant (P < 0.0001) components of total facial asymmetry. Fluctuating asymmetry was slightly associated with age (r = 0.0858, P = 0.0414) and there were no differences between geographical regions (P = 0.413). Attractiveness was not correlated to levels of asymmetry in either sex (males: P = 0.0973; females P = 0.7415).

CONCLUSIONS

Asymmetry was a prevalent feature in the present sample, and preferences for symmetric faces were not operating in the studied population.

Male Facial Anthropometry and Attractiveness

The symmetry and masculinity of the face are often considered important elements of male facial attractiveness. However, facial preferences are rarely studied on natural faces. We studied the effect of these traits and facial metric parameters on facial attractiveness in Spanish and Colombian raters. In total, 13 metric and 11 asymmetry parameters from natural, unmanipulated frontal face photographs of 50 Spanish men were measured with the USIA semiautomatic anthropometric software. All raters (women and men) were asked to rank these images as potential long-term partners for females. In both sexes, facial attractiveness was negatively associated with facial masculinity, and preference was not associated with facial symmetry. In Spanish raters, both sexes preferred male traits that were larger in the right side of the face, which may reflect a human tendency to prefer a certain degree of facial asymmetry. We did not find such preference in Colombian raters, but they did show stronger preference for facial femininity than Spanish raters. Present results suggest that facial relative femininity, which is expected to signal, eg good parenting and cooperation skills, may be an important signal of mate quality when females seek long-term partners. Facial symmetry appears unimportant in such long-term mating preferences.