Brain responses to facial attractiveness induced by facial proportions: evidence from an fMRI study

Evaluation of Surgical Outcomes and Patient-reported Outcomes of Eyebrow Defect Repair with "Kite Flap"

There is no consensus on the surgical options for repairing mild-to-moderate eyebrow defects due to burns, trauma, and skin tumors, and the outcome of the surgery is unclear. In this study, the authors evaluated the surgical outcomes and patient-reported outcomes of eyebrow defect repair with the "kite flap" in a cross-sectional study. Case data and imaging data of twelve patients with eyebrow defects undergoing repair from July 2018 to June 2021 were retrospectively analyzed, and the surgical outcomes were statistically analyzed by the Face-Q subjective evaluation scale and the surgical objective evaluation scale. In the postoperative objective evaluation, 66.67% of the patients were "very satisfied," and the scores of the Face-Q scale for the assessment of appearance and psychosocial function were significantly improved compared with those of the preoperative period, with a statistically significant difference in the data changes (P<0.05). The study showed that the "kite flap" is an excellent surgical method for repairing mild-to-moderate defects of the eyebrow, and it can meet the requirements of both function and appearance after surgery.

Defining Ideal Double Eyelids With a Morphometric Analysis in Asians

BACKGROUND

Double eyelids are always considered crucial aesthetic symbols. Despite numerous studies conducted on the attractiveness of double eyelids, there remains a dearth of research on quantitative and morphological evaluation of ideal double eyelids.

OBJECTIVES

In this we study aimed to investigate the optimal height and morphological characteristics of ideal double eyelids.

METHODS

Participants were presented with a total of 9 images, consisting of 1 single eyelid image and 8 double eyelid images, featuring 2 distinct shapes and 4 varied pretarsal shows. Respondents were instructed to assign scores ranging from 1 (least attractive) to 5 (most attractive) for each image. Subsequently, the scores for each image were analyzed based on population demographics, followed by the calculation of aesthetic metrics.

RESULTS

The whole cohort deemed images with a 2-mm fold to be more attractive than 1 mm (P < .001), followed by 3 mm and 0 mm (single eyelid), and finally, 4 mm. Morphologically, significant differences were found between images with the same pretarsal shows of 3 mm (P < .001) and 4 mm (P = .026). Most subgroup analysis results were aligned with those of the cohort, with gender being the most significant factor in distinguishing double eyelid aesthetics. Additionally, aesthetic characteristics of 2-mm folds were found to be comparable to appealing double eyelids in previous studies.

CONCLUSIONS

In this study we validated the optimal heights and morphology of double eyelids, thereby addressing the existing gap in aesthetic studies on double eyelids. These findings hold significant implications for surgical planning, effect assessment, and other periocular procedures related to upper blepharoplasty.

LEVEL OF EVIDENCE: 4

Neural Mechanisms of the Conscious and Subliminal Processing of Facial Attractiveness

The purpose of this study was to investigate the neural activity evoked by facial attractiveness in conscious and subliminal conditions. The 41 participants judged facial attractiveness in a conscious condition and a subliminal condition (backward masking paradigm). The event-related potential (ERP) analysis indicated that in the conscious condition, more attractive faces elicited a longer N1 (80-120 ms) latency than less attractive faces. Moreover, more attractive female faces elicited a larger late positive component (LPC) (350-550 ms) amplitude than less attractive female faces. In the subliminal condition, more attractive faces elicited a longer P1 (140-180 ms) latency than less attractive faces. The present study demonstrated that more attractive faces evoked different early-stage ERPs from that evoked by less attractive faces in both conscious and subliminal conditions. However, the processing of facial attractiveness is obviously weakened in the subliminal condition.

Neural Correlates and Perceived Attractiveness of Male and Female Shoulder-to-Hip Ratio in Men and Women: An EEG Study

While there are studies regarding the neural correlates of human facial attractiveness, there are few investigations considering neural responses for body form attractiveness. The most prominent physical feature defining men's attractiveness is their physical fitness and upper body strength. Shoulder-to-hip ratio (SHR), a sexually dimorphic trait in humans, is an indicator of men's attractiveness for both men and women. The current study is the first to report on the neurophysiological responses to male and female body forms varying in SHR in healthy heterosexual men and women observers. Electroencephalographic (EEG) signals were acquired while participants completed an oddball task as well as a subsequent attractiveness judgement task. Behavioral results showed larger SHRs were considered more attractive than smaller SHRs, regardless of stimuli and participants' sex. The electrophysiological results for both the oddball task and the explicit judgement of attractiveness showed that brain activity related to male SHR body stimuli differed depending on the specific ratios, both at early and late processing stages. For female avatars, SHR did not modulate neural activity. Collectively the data implicate posterior brain regions in the perception of body forms that differ in attractiveness vis-a-vis variation of SHR, and frontal brain regions when such perceptions are rated explicitly.

Quantitative analysis of facial proportions and facial attractiveness among Asians and Caucasians

It has been proposed that the proportions of the human face are crucial for facial aesthetics. If this is the case, we should describe the relationship among proportions of face components quantitatively. This study aims to develop a mathematical model of facial proportions to provide a quantitative description of facial attractiveness. Furthermore, we expect that plastic surgeons can use models in clinical work to enhance communication efficiency between doctors and patients. Face alignment technique was used to analyse 5500 frontal faces with diverse properties (male/female, Asian/Caucasian, ages) to obtain the ratios among the nose length ($ {N}_{L} $), the nasal base width ($ N $), and the inner canthus width ($ {E}_{I} $). A mathematical model ($ {N}_{L}^{2} = a{E}_{I}\mathrm{*}{N}_{L}+b{E}_{I}\mathrm{*}N+cN\mathrm{*}{N}_{L} $) was developed to describe the relationship among these proportions. To validate the effectiveness of this approach, we simulated the post-operative photos using Adobe Photoshop. Our findings show that the ratio of nose length to nose width, the ratio of inner canthus width to nose length and the ratio of inner canthus to nose width play a significant role in determining facial attractiveness. These results provide a possible strategy to quantitatively describe the relationship among human face proportions.

Three-Dimensional Analysis of Posterior Mandibular Displacement in Rats

Mandibular protrusion and its treatment is challenging for the orthodontist. The aim of the present research was to identify macroscopic changes in the mandible, based on three-dimensional Cone Beam Computed Tomography analysis. Seventy-two male Wistar rats were divided into two equal groups, experimental (group A) and control (group B). Each consisted of three equal subgroups of 12 rats (A1, A2, A3, B1, B2, B3). Full-cast orthodontic intraoral devices were attached to the maxillary incisors of the experimental animals, and effected functional posterior mandibular displacement. Throughout the experimental period, all animals were fed with mashed food. Animals were sacrificed at 30 days (A1, B1), 60 days (A2, B2) and 90 days (A3, B3). At the 60th day of the experiment, the orthodontic devices were removed from the remaining experimental subgroup A3. Measurements revealed significant differences in the anteroposterior dimensions between experimental and control subgroups. However, the observed changes in the vertical dimensions, Condylion/Go’–Menton and the Intercondylar distance proved insignificant. Posterior mandibular displacement of the mandible in growing rats affects the morphology of the mandible and culminates in the development of a smaller mandible at a grown age.

Application of Empirical Mode Decomposition for Decoding Perception of Faces Using Magnetoencephalography

Neural decoding is useful to explore the timing and source location in which the brain encodes information. Higher classification accuracy means that an analysis is more likely to succeed in extracting useful information from noises. In this paper, we present the application of a nonlinear, nonstationary signal decomposition technique—the empirical mode decomposition (EMD), on MEG data. We discuss the fundamental concepts and importance of nonlinear methods when it comes to analyzing brainwave signals and demonstrate the procedure on a set of open-source MEG facial recognition task dataset. The improved clarity of data allowed further decoding analysis to capture distinguishing features between conditions that were formerly over-looked in the existing literature, while raising interesting questions concerning hemispheric dominance to the encoding process of facial and identity information.

Does Surgeon Gender Matter for Aesthetic Patients?

BACKGROUND

Plastic surgery patients have expectations for an ideal practice to visit. However, patients' preferences regarding their plastic surgeon are still being described.

OBJECTIVES

The aim of this study was to investigate if elective cosmetic plastic surgery patients exhibit gender preference in their plastic surgeon when making online inquiries.

METHODS

A retrospective, single-practice review of all online inquiries for elective plastic surgery and nonsurgical injectable treatment from June 2019 to June 2020 was performed. The study was based on a private practice located in Houston, TX. The practice surgeons were a married couple, 1 female and 1 male, with identical training, age, and post-residency experience. Patients submitted an online inquiry for their procedure of interest and surgeon preference via the practice website.

RESULTS

The private practice received 873 online inquiries during the year-long study period. The majority of patients were female, 855 (97.9%), and the remaining 18 (2.1%) were male. Of the female patients, 476 (55.7%) preferred a female surgeon and 138 (16.1%) preferred a male surgeon; 241 (28.2%) female patients expressed no surgeon preference. Regardless of surgeon preference, the majority of procedures inquired about were breast and body contouring.

CONCLUSIONS

This cohort of female patients prefers the female surgeon for breast procedures or multiple procedures involving the breast, and the male surgeon for injectable procedures and facial procedures. There is no preference for the male or female surgeon for body procedures. Female plastic surgery patients may be influenced by surgeon gender in choosing their surgeon, depending on their surgery of interest.

Seven computations of the social brain

The social environment presents the human brain with the most complex information processing demands. The computations that the brain must perform occur in parallel, combine social and nonsocial cues, produce verbal and nonverbal signals and involve multiple cognitive systems, including memory, attention, emotion and learning. This occurs dynamically and at timescales ranging from milliseconds to years. Here, we propose that during social interactions, seven core operations interact to underwrite coherent social functioning; these operations accumulate evidence efficiently-from multiple modalities-when inferring what to do next. We deconstruct the social brain and outline the key components entailed for successful human-social interaction. These include (i) social perception; (ii) social inferences, such as mentalizing; (iii) social learning; (iv) social signaling through verbal and nonverbal cues; (v) social drives (e.g. how to increase one's status); (vi) determining the social identity of agents, including oneself and (vii) minimizing uncertainty within the current social context by integrating sensory signals and inferences. We argue that while it is important to examine these distinct aspects of social inference, to understand the true nature of the human social brain, we must also explain how the brain integrates information from the social world.

The Ideal Lips: Lessons Learnt from the Literature

Defining the ideal dimensions and proportions of the human face has been attempted for centuries, popularised in the Renaissance period by artists including Leonardo Da Vinci. The lips are part of the lower third of the face and are central to lower face aesthetics and the overall symmetry of the face. They also place an important part in conveying facial emotions and expressions. Full lips with well-defined Cupid's bow have always been associated with youth and beauty. The approval of hyaluronic acid use for tissue augmentation and the prevalence of social media have caused an exponential increase in lip augmentation procedures (Linkov et al. in Arch Plast Surg 46(3):248-254, 2019), as such researchers and aestheticians have focused on characterising the ideal lips mathematically to help guide clinicians. This narrative review will summarise the available evidence in the literature pertaining to the ideal lips, taking into account age, ethnicity and gender differences. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Assessing Facial Symmetry and Attractiveness using Augmented Reality

Facial symmetry is a key component in quantifying the perception of beauty. In this paper, we propose a set of facial features computed from facial landmarks which can be extracted at a low computational cost. We quantitatively evaluated the proposed features for predicting perceived attractiveness from human portraits on four benchmark datasets (SCUT-FBP, SCUT-FBP5500, FACES and Chicago Face Database). Experimental results showed that the performance of the proposed features is comparable to those extracted from a set with much denser facial landmarks. The computation of facial features was also implemented as an augmented reality (AR) app developed on Android OS. The app overlays four types of measurements and guidelines over a live video stream, while the facial measurements are computed from the tracked facial landmarks at run time. The developed app can be used to assist plastic surgeons in assessing facial symmetry when planning reconstructive facial surgeries.

Stability test of canonical correlation analysis for studying brain-behavior relationships: The effects of subject-to-variable ratios and correlation strengths

Canonical correlation analysis (CCA), a multivariate approach to identifying correlations between two sets of variables, is becoming increasingly popular in neuroimaging studies on brain‐behavior relationships. However, the CCA stability in neuroimaging applications has not been systematically investigated. Although it is known that the number of subjects should be greater than the number of variables due to the curse of dimensionality, it is unclear at what subject‐to‐variable ratios (SVR) and at what correlation strengths the CCA stability can be maintained. Here, we systematically assessed the CCA stability, in the context of investigating the relationship between the brain structural/functional imaging measures and the behavioral measures, by measuring the similarity of the first‐mode canonical variables across randomly sampled subgroups of subjects from a large set of 936 healthy subjects. Specifically, we tested how the CCA stability changes with SVR under two different brain‐behavior correlation strengths. The same tests were repeated using an independent data set (n = 700) for validation. The results confirmed that both SVR and correlation strength affect greatly the CCA stability—the CCA stability cannot be guaranteed if the SVR is not sufficiently high or the brain‐behavior relationship is not sufficiently strong. Based on our quantitative characterization of CCA stability, we provided a practical guideline to help correct interpretation of CCA results and proper applications of CCA in neuroimaging studies on brain‐behavior relationships.

Human brain activity reflecting facial attractiveness from skin reflection

Facial attraction has a great influence on our daily social interactions. Previous studies have mainly focused on the attraction from facial shape and expression. We recently found that faces with radiant skin appear to be more attractive than those with oily-shiny or matte skin. In the present study, we conducted functional magnetic resonance imaging (fMRI) and psychological experiments to determine the human brain activity that reflects facial attractiveness modulated by these skin reflection types. In the fMRI experiment, female subjects were shown successive images of unfamiliar female faces with matte, oily-shiny, or radiant skin. The subjects compared each face with the immediately preceding face in terms of attractiveness, age, and skin reflection, all based on the skin. The medial part of the orbitofrontal cortex (mOFC) was significantly more active when comparing attractiveness than when comparing skin reflection, suggesting that the mOFC is involved in processing facial attractiveness from skin reflection. In the psychological experiment, attractiveness rating was highest for radiant skin, followed by oily-shiny, and then matte skin. Comparison of the results of these experiments showed that mOFC activation level increased with attractiveness rating. These results suggest that the activation level of the mOFC reflects facial attractiveness from skin reflection.

Male brain processing of the body odor of ovulating women compared to that of pregnant women

Female chemical signals underlie the advertising of sexual receptivity and fertility. Whether the body odor of a pregnant woman also has a signaling function with respect to male behavior is yet to be conclusively established. This study examines how the body odors of ovulating and pregnant women differentially affect the behavior of heterosexual men. Body odor samples were collected from 5 pregnant women and 5 matched controls during ovulation. In a double-blind functional magnetic resonance imaging design, 18 heterosexual men were exposed to female body odors during ovulation (OV) and pregnancy (PRG) while being required to indicate the attractiveness of concurrently presented female portrait images. The participants were also required to indicate whether they assumed a depicted woman was pregnant. While neither OV nor PRG altered the perceived attractiveness of a presented face, the men tended to identify the women as pregnant while exposed to a PRG body odor. On the neural level, OV activated a network of the frontotemporal and limbic regions, while PRG activated the superior medial frontal gyrus. The results suggest that the detection of sexual availability activates the male brain regions associated with face processing and reward/motivation, whereas sensing pregnancy activates a region responsible for empathy and prosocial behavior. Thus, the female body odor during pregnancy likely helps foster circumstances conducive to the future care of offspring while the body odor advertising sexual availability promotes mating behavior. The brains of heterosexual men may be capable of unconsciously discriminating between these two types of olfactory stimuli.

Double-Incision approach with suspension of the orbicularis oculi muscle and relieving of tension for upper eyelid rejuvenation in Asian women

BACKGROUND

In Asian women, upper eyelid skin laxity, lateral hooding, and upper eyelid and brow asymmetry in the aging upper eyelid are prominently and frequently seen. It is difficult to completely resolve these problems with the classical single-incision method. In this study, we investigate the utility of a double-incision approach to address aging-related changes of the upper eyelid.

METHODS

From September 2017 to March 2019, 51 patients underwent this procedure. Through a sub-brow incision, the skin and subcutaneous tissue were excised and the orbicularis oculi muscle (OOM) flap and muscular-cutaneous flap were separated. The OOM flap was lifted and fixed to the periosteum through the sub-brow fat pad and covered by the upper muscular-cutaneous flap. Through an eyelid crease incision, the supratarsal upper eyelid skin, muscle, and orbital fat were excised, excessive tension was alleviated, and double-fold eyelids were adjusted and reshaped if needed. The results were evaluated by asking the surgeon and patient involved to allocate a categorical (poor, fair, good, very good, excellent) scores and comparisons between pre- and postoperative brow position.

RESULTS

The average follow-up period was 12 months. Most patients were satisfied with the results, barring two cases each of vomiting and transient numbness over the forehead region and three revisions. The mean surgeon and patient categorical scores associated with satisfaction with the overall outcome at 6 months were 4.2 ± 0.6 (range 3.0-5.0) and 4.0 ± 0.7 (range 2.0-5.0), respectively. The brow position was stable during follow-up period.

CONCLUSION

A double-incision approach is a safe, effective, durable, and esthetic way for treating patients presenting with upper eyelid aging.

Seeking the "Beauty Center" in the Brain: A Meta-Analysis of fMRI Studies of Beautiful Human Faces and Visual Art

During the past two decades, cognitive neuroscientists have sought to elucidate the common neural basis of the experience of beauty. Still, empirical evidence for such common neural basis of different forms of beauty is not conclusive. To address this question, we performed an activation likelihood estimation (ALE) meta-analysis on the existing neuroimaging studies of beauty appreciation of faces and visual art by nonexpert adults (49 studies, 982 participants, meta-data are available at https://osf.io/s9xds/ ). We observed that perceiving these two forms of beauty activated distinct brain regions: While the beauty of faces convergently activated the left ventral striatum, the beauty of visual art convergently activated the anterior medial prefrontal cortex (aMPFC). However, a conjunction analysis failed to reveal any common brain regions for the beauty of visual art and faces. The implications of these results are discussed.

Putative ratios of facial attractiveness in a deep neural network

Empirical evidence has shown that there is an ideal arrangement of facial features (ideal ratios) that can optimize the attractiveness of a person's face. These putative ratios define facial attractiveness in terms of spatial relations and provide important rules for measuring the attractiveness of a face. In this paper, we show that a deep neural network (DNN) model can learn putative ratios from face images based only on categorical annotation when no annotated facial features for attractiveness are explicitly given. To this end, we conducted three experiments. In Experiment 1, we trained a DNN model to recognize the attractiveness (female/male × high/low attractiveness) of face in the images using four category-specific neurons (CSNs). In Experiment 2, face-like images were generated by reversing the DNN model (e.g., deconvolution). These images depict the intuitive attributes encoded in CSNs of the four categories of facial attractiveness and reveal certain consistencies with reported evidence on the putative ratios. In Experiment 3, simulated psychophysical experiments on face images with varying putative ratios reveal changes in the activity of the CSNs that are remarkably similar to those of human judgements reported in a previous study. These results show that the trained DNN model can learn putative ratios as key features for the representation of facial attractiveness. This finding advances our understanding of facial attractiveness via DNN-based perspective approaches.

A technical review of canonical correlation analysis for neuroscience applications

Collecting comprehensive data sets of the same subject has become a standard in neuroscience research and uncovering multivariate relationships among collected data sets have gained significant attentions in recent years. Canonical correlation analysis (CCA) is one of the powerful multivariate tools to jointly investigate relationships among multiple data sets, which can uncover disease or environmental effects in various modalities simultaneously and characterize changes during development, aging, and disease progressions comprehensively. In the past 10 years, despite an increasing number of studies have utilized CCA in multivariate analysis, simple conventional CCA dominates these applications. Multiple CCA-variant techniques have been proposed to improve the model performance; however, the complicated multivariate formulations and not well-known capabilities have delayed their wide applications. Therefore, in this study, a comprehensive review of CCA and its variant techniques is provided. Detailed technical formulation with analytical and numerical solutions, current applications in neuroscience research, and advantages and limitations of each CCA-related technique are discussed. Finally, a general guideline in how to select the most appropriate CCA-related technique based on the properties of available data sets and particularly targeted neuroscience questions is provided.

Becoming sexy: Contrapposto pose increases attractiveness ratings and modulates observers' brain activity

Previous neurophysiological studies have revealed the neural correlates of human body form perception, as well as those related to the perception of attractive body sizes. In the current study we aimed to extend the neurophysiological studies regarding body perception by investigating the perception of human body posture to provide insights into the cognitive mechanisms responsive to bodily form, and the processing of its attractiveness. To achieve these aims, we used the contrapposto posture which creates an exaggeration of low waist to hip ratio (WHR), an indicator of women's attractiveness. Electroencephalogram (EEG) signals were recorded while participants completed both (i) an oddball task presenting female body forms differing in pose (contrapposto vs. standing) and viewing angle (anterior vs. posterior), and (ii) a subsequent active attractiveness judgement task. Behavioral results showed that a contrapposto pose is considered more attractive than a neutral standing pose. Results at the neural level showed that body posture modulates the visual information processing in early ERP components, indicating attentional variations depending on human body posture; as well as in late components, indicating further differences in attention and attractiveness judgement of stimuli varying in body pose. Furthermore, the LORETA results identified the middle temporal gyrus as well as angular gyrus as the key brain regions activated in association with the perception and attractiveness judgment of females' bodies with different body poses. Overall, the current paper suggests the evolutionary adaptive preference for lower WHRs as in the contrapposto pose activating brain regions associated with visual perception and attractiveness judgement.

Subjectivity and complexity of facial attractiveness

The origin and meaning of facial beauty represent a longstanding puzzle. Despite the profuse literature devoted to facial attractiveness, its very nature, its determinants and the nature of inter-person differences remain controversial issues. Here we tackle such questions proposing a novel experimental approach in which human subjects, instead of rating natural faces, are allowed to efficiently explore the face-space and "sculpt" their favorite variation of a reference facial image. The results reveal that different subjects prefer distinguishable regions of the face-space, highlighting the essential subjectivity of the phenomenon. The different sculpted facial vectors exhibit strong correlations among pairs of facial distances, characterising the underlying universality and complexity of the cognitive processes, and the relative relevance and robustness of the different facial distances.

Smile prevails over other facial components of male facial esthetics

BACKGROUND

The aim of this study was to assess whether scores assigned to the eyes, nose, mouth, and chin regions work as predictors of full smiling face scores.

METHODS

In this cross-sectional study, the authors used the facial photographs of 86 smiling men. Photographs yielded 5 components: 1 of the face itself and 4 subcomponents (eyes, nose, mouth, and chin region). Raters assigned the photographs beauty scores that the authors measured morphometrically. The authors analyzed the predictive ability of the subcomponents against that of the full face.

RESULTS

The subcomponents were statistically significant predictors of facial beauty (mouth: r² = 0.38, P < .0001; eyes: r² = 0.14, P < .0001; chin region: r² = 0.09, P < .0001; nose: r² = 0.02, P = .05). The more beautiful people had several statistically significant characteristics, such as narrower faces.

CONCLUSIONS

Facial subcomponents are predictive factors of the male smiling face and contribute in the following descending order of importance: mouth, eyes, chin region, and nose.

PRACTICAL IMPLICATIONS

The results suggest that for many people improvement in smile esthetics also likely will exert a more positive effect on facial beauty than will other procedures (for example, rhinoplasty).

Chen's Double Eyelid Fold Illusion: An Eye Size Assimilation Illusion Induced by a Supratarsal Fold in the Brow-Eye Unit, A Preliminary Report

BACKGROUND

Double eyelidplasty can enhance the eye size and facial attractiveness of Asian individuals with single eyelids. The authors hypothesize that a supratarsal fold can induce an eye size assimilation illusion to enhance eye dimensions and aesthetics, and seek to define the optimum vertical proportion between a supratarsal fold and the eye fissure associated with maximal induction of the size assimilation illusion.

METHODS

A photometric study of the replicated photographs of ten female Taiwanese patients after double eyelidplasty was designed. Each photograph was edited by shifting the supratarsal folds vertically at a regular fold/eye ratio increment of 0.1. The perceived attractiveness of edited photographs of each patient was rated by 100 adult observers using a score of 1-5. The palpebral parameters were measured and analyzed.

RESULTS

The mean rating score increased gradually when a supratarsal fold was added and peaked when the fold/eye ratio was 0.3 and the mean Chen's double eyelid fold ratio was 0.631 ± 0.023. After the peak, the mean score decreased gradually and was lower than the photograph without a fold when the fold/eye ratio exceeded 0.5 and the mean Chen's ratio exceeded 0.729 ± 0.027.

CONCLUSION

Within the optimal ranges of the fold/eye ratio and Chen's double eyelid fold ratio, eyes are perceived as larger and more attractive due to a hybrid presentation of two interdependent eye size assimilation illusions induced by a supratarsal fold in the brow-eye unit. "Chen's double eyelid fold illusion" is proposed to describe this complex visual phenomenon.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Hello handsome! Male's facial attractiveness gives rise to female's fairness bias in Ultimatum Game scenarios-An ERP study

The current study delineated how male proposers’ facial attractiveness affect female responders’ fairness considerations and their subsequent decision outcome during the Ultimatum Game (UG). Event Related Potentials (ERPs) were recorded from 17 female subjects, who played the role as responders and had to decide whether to accept offers from either attractive or unattractive male proposers. Behavioral data (Acceptance Ratio and Response time) revealed that, more offers were accepted from attractive-face conditions; subjects typically responded quicker to unfair offers from unattractive proposers as compared with slower to unfair offers from attractive proposers. The ERP data demonstrated similar N2 amplitudes elicited by both attractive and unattractive faces, and a larger early frontal LPP elicited by the attractive faces compared with unattractive ones, but no significant differences of both late posterior LPP and typical parietal LPP amplitudes were observed between these two face conditions, which was different from our previous study with similar paradigm but male participants. The results suggest that, in comparison to males, females might not experience the potential attention bias towards unattractive opposite-sex faces and are less likely to possess an enhanced processing and evaluation of those faces. This phenomenon might be explained by endogenous gender differences in mate preference. The feedback-related negativity (FRN) and P300 responses during an offer presentation were further measured in both attractive-face and unattractive-face conditions and the results demonstrated that the amplitudes elicited by fair and unfair offers were not statistically different in the former condition, but were different in the latter condition. More specifically, unfair offers generated larger FRN and smaller P300 than fair ones in the unattractive-face condition. Findings suggest that, although females tend to possess less salient evaluation of male’s facial attractiveness, the attractiveness of male proposers would still attenuate female responders’ fairness consideration during the UG.