Skin blood perfusion and oxygenation colour affect perceived human health

Recent advances of electrospun strategies in topical products encompassing skincare and dermatological treatments

As the potential applications of electrospinning in healthcare continue to be explored, along with advancements in industrial-scale solutions and the emergence of portable electrospinning devices, some researchers have explored electrospinning technology in topical products, including its application in skincare, such as facial masks, beauty patches, sunscreen, and dermatological treatments for conditions like atopic dermatitis, psoriasis, acne, skin cancer, etc. In this review, we first outline the fundamental principles of electrospinning and provide an overview of existing solutions for large-scale production and the components and functionalities of portable spinning devices. Based on the essential functionalities required for skincare products and the mechanisms and treatment methods for the aforementioned dermatological diseases, we summarize the potential advantages of electrospinning technology in these areas, including encapsulation, sustained release, large surface area, and biocompatibility, among others. Furthermore, considering the further commercialization and clinical development of electrospinning technology, we offer our insights on current challenges and future perspectives in these areas, including issues such as ingredients, functionality, residue concerns, environmental impact, and efficiency issues.

Variation in Skin Red and Yellow Undertone: Reliability of Ratings and Relevance for Perceived Social Experiences

It is well established that skin lightness-darkness is associated with social outcomes, but little is known regarding the social salience of skin undertones (redness and yellowness). Our study addresses two related research questions on this topic: first, we ask whether red and yellow undertones are consistently perceived by observers; second, we ask whether red and yellow undertones are associated with expectations of discrimination across a range of social settings. We address these questions using novel survey data in which skin lightness-darkness and undertones are captured using CIELAB measurements and a two-dimensional categorical skin color scale. Although we find skin lightness-darkness to be the strongest and most consistent predictor of discrimination expectations, respondents also perceived skin undertones consistently, and skin yellowness was associated with a higher predicted likelihood of discrimination net of lightness-darkness in certain social settings. Our findings suggest that colorism can extend beyond a light-dark binary and emphasize the value of capturing undertones, particularly yellowness, in social surveys assessing skin color.

Mate assessment based on physical characteristics: a review and reflection

Mate choice, and sex differences in romantic behaviours, represented one of the first major applications of evolutionary biology to human behaviour. This paper reviews Darwinian approaches to heterosexual mate assessment based on physical characteristics, placing the literature in its historical context (1871-1979), before turning (predominantly) to psychological research on attractiveness judgements based on physical characteristics. Attractiveness is consistently inferred across multiple modalities, with biological theories explaining why we differentiate certain individuals, on average, from others. Simultaneously, it is a judgement that varies systematically in light of our own traits, environment, and experiences. Over 30 years of research has generated robust effects alongside reasons to be humble in our lack of understanding of the precise physiological mechanisms involved in mate assessment. This review concludes with three questions to focus attention in further research, and proposes that our romantic preferences still provide a critical window into the evolution of human sexuality.

Association between the three-dimensional facial shape and its color in a boundary group of young to middle-aged Asian women

Visual cues strongly influence an individual's self-esteem and have fundamental sociopsychological functions. The color and shape of the face are important information for visual cues and are hypothesized to be correlated with each other. However, few studies have examined these relationships. Thus, this study determined the association between color and shape of the face. For this purpose, we evaluated Chinese women in their 30s and 40s (n = 166). Three-dimensional (3D) image-capture devices that provide shape morphology along with standardized photographs (color information) were used to obtain 3D images of women. The coordinates and red‒green-blue color data on the 3D images were utilized to perform principal component (PC) analysis, and shape and color PCs were generated. A canonical variate analysis was then conducted to check for significant correlations between the shape and color PCs. As a result, 6 significant correlations were found (p < 0.05). In detail, in addition to the physical correlations (i.e., steric faces or faces with protrusion of the cheek showed greater shadows, retrognathism was related to a shadow under the lower lip and vice versa), biological correlations (fatty faces showed greater redness and remarkable marionette lines; faces with age-related sagging showed greater darkness, possibly related to cumulative ultraviolet radiation exposure of the skin; and robust mandibles and supraorbital ridges were related to thick eyebrows) were found. This insight can aid both medical and cosmetic practitioners in comprehending the intricate details conveyed by facial features, thereby facilitating more comprehensive diagnosis and treatment planning, including makeup.

Skin homeostasis: Mechanism and influencing factors

BACKGROUND

The skin is the largest organ in the human body, not only resisting the invasion of harmful substances, but also preventing the loss of moisture and nutrients. Maintaining skin homeostasis is a prerequisite for the proper functioning of the body. Any damage to the skin can lead to a decrease in local homeostasis, such as ultraviolet radiation, seasonal changes, and air pollution, which can damage the skin tissue and affect the function of the skin barrier.

OBJECTIVE

This article reviews the maintenance mechanism and influencing factors of skin homeostasis and the symptoms of homeostasis imbalance.

METHODS

We searched for articles published between 1990 and 2022 in English and Chinese using PubMed, Web of Science, CNKI, and other databases in the subject area of dermatology, using the following search terms in various combinations: "skin homeostasis," "skin barrier," and "unstable skin." Based on our results, we further refined our search criteria to include a series of common skin problems caused by the destruction of skin homeostasis and its treatments. Limitations include the lack of research on dermatological and cosmetic problems triggered by the disruption of skin homeostasis.

RESULTS

This study describes the neuroendocrine-immune system, skin barrier structure, and skin metabolic system that maintain skin homeostasis. In addition, we discuss several common symptoms that occur when skin homeostasis is out of balance, such as dryness, redness, acne, sensitivity, and aging, and explain the mechanism of these symptoms.

CONCLUSION

This article provides an update and review for students and practitioners, and provides a theoretical basis for the development of skin care products for the maintenance and repair of skin homeostasis.

Disordered spatial pattern of redness signal on facial skin and visual perception of health, stress, and hidden aging

BACKGROUND

Well-being is commonly communicated across industries; however, experimental understanding how human perceive skin health and skin stresses are not sufficient.

MATERIALS AND METHODS

Image analysis algorithm, a* gradient, was developed to evaluate spatial pattern and shape of red signal on skin. Human perception for skin health and stresses were compared with technical measurements in two visual perception studies.

RESULTS

a* gradient correlated with perceived Inflamed Skin (R = 0.73, p < 0.01), Stressed Skin (R = 0.79, p < 0.01), Sensitive Skin (R = 0.75, p < 0.01), Healthy Skin (R = -0.83, p < 0.01), and Start Aging (R = 0.75, p < 0.01).

CONCLUSIONS

Disordered spatial pattern of redness signal drives human perception of skin health, stress, and aging. This new skin index of redness signal shows higher correlation with those human perception than basal a* mean, unevenness of a*, and other conventional skin color attributes.

A novel multi-feature learning model for disease diagnosis using face skin images

BACKGROUND

Facial skin characteristics can provide valuable information about a patient's underlying health conditions.

OBJECTIVE

In practice, there are often samples with divergent characteristics (commonly known as divergent samples) that can be attributed to environmental factors, living conditions, or genetic elements. These divergent samples significantly degrade the accuracy of diagnoses.

METHODOLOGY

To tackle this problem, we propose a novel multi-feature learning method called Multi-Feature Learning with Centroid Matrix (MFLCM), which aims to mitigate the influence of divergent samples on the accurate classification of samples located on the boundary. In this approach, we introduce a novel discriminator that incorporates a centroid matrix strategy and simultaneously adapt it to a classifier in a unified model. We effectively apply the centroid matrix to the embedding feature spaces, which are transformed from the multi-feature observation space, by calculating a relaxed Hamming distance. The purpose of the centroid vectors for each category is to act as anchors, ensuring that samples from the same class are positioned close to their corresponding centroid vector while being pushed further away from the remaining centroids.

RESULTS

Validation of the proposed method with clinical facial skin dataset showed that the proposed method achieved F1 scores of 92.59%, 83.35%, 82.84% and 85.46%, respectively for the detection the Healthy, Diabetes Mellitus (DM), Fatty Liver (FL) and Chronic Renal Failure (CRF).

CONCLUSION

Experimental results demonstrate the superiority of the proposed method compared with typical classifiers single-view-based and state-of-the-art multi-feature approaches. To the best of our knowledge, this study represents the first to demonstrate concept of multi-feature learning using only facial skin images as an effective non-invasive approach for simultaneously identifying DM, FL and CRF in Han Chinese, the largest ethnic group in the world.

Predictors of female age, health and attractiveness perception from skin feature analysis of digital portraits in five ethnic groups

OBJECTIVE

Research indicates the impact of skin colour, tone evenness and surface topography on ratings of age, health and attractiveness in women. In addition to subjective assessments, these effects have been quantified with objective measures derived from skin image analysis. Signs of skin ageing may manifest differently across ethnic groups. However, comparisons have been limited to research with two ethnic groups, preventing conclusions about an ethnicity-specific ranking of skin ageing signs.

METHODS

We report results from a multi-ethnic and multi-centre study in which faces of women (n = 180; aged 20-69 years) from five ethnic groups were imaged. Facial images were rated for age, health and attractiveness by members of the same ethnic group (each n = 120). Digital image analysis was used to quantify skin colour, gloss, tone evenness and wrinkling/sagging. We assessed associations between face ratings and skin image measurements in the total sample (i.e. all ethnic groups) and separately by ethnicity.

RESULTS

Skin image analysis revealed differences between ethnic groups, including skin colour, gloss, tone evenness, wrinkling and sagging. Differences in the relative predictive utility of individual skin features in accounting for ratings of age, health and attractiveness also were observed between ethnic groups. Facial wrinkling and sagging were the best predictors of face ratings in each ethnic group, with some differences in the type (or predictive magnitude) of skin features.

CONCLUSION

The current findings corroborate previous reports of differences between ethnic groups in female facial skin and indicate differential effects of skin features on ratings of age, health and attractiveness, within and between ethnic groups. Facial wrinkling and sagging were the best predictors of age and attractiveness ratings, and skin tone evenness and gloss had an additional role in ratings of health.

Colour information biases facial age estimation and reduces inter-observer variability

Age estimation is a perceptual task that people perform automatically and effortlessly on a daily basis. Colour has been identified as one of the facial cues that contributes to age perception. To investigate further the role of colour in age perception, we manipulated the chromatic content of facial images holistically. In Experiment 1, images were shown in colour or grey scale; in Experiment 2, images were shown with red-green contrast increased or decreased; in Experiment 3, images were shown with modified yellow-blue contrast. We examined whether the presence of chromatic information biases the perception of age and/or affects inter-observer variability in age judgements, and whether specific chromatic information affects the perception of age. We found that the same face tended to be judged as younger with increased red-green contrast compared to decreased red-green contrast, suggesting that red-green contrast directly affects age perception. Inter-observer variability in age ratings was significantly lower when participants were asked to rate colour compared with grey scale versions of images. This finding indicates that colour carries information useful cues for age estimation.

Efficacy and Safety of the Genistein Nutraceutical Product Containing Vitamin E, Vitamin B3, and Ceramide on Skin Health in Postmenopausal Women: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Skin aging is one of the most concerning issues that occur after menopause. The Genistein Nutraceutical (GEN) product, containing genistein, vitamin E, vitamin B3, and ceramide, has been formulated as a topical anti-aging product for improving the health of postmenopausal women's facial skin. This study aimed to investigate the efficacy and safety of the GEN product on postmenopausal women's facial skin. This randomized, double-blind, placebo-controlled trial randomly assigned 50 postmenopausal women to receive either the GEN product (n = 25) or the placebo (PLA) product (n = 25), topically applied twice daily for 6 weeks. The outcome assessments included multiple skin parameters related to skin wrinkling, color, hydration, and facial skin quality at baseline and week 6. The percentage mean changes or absolute mean changes, where appropriate, in skin parameters were compared between the two groups. The mean age of the participants was 55.8 ± 3.4 years. For skin wrinkling and skin color parameters, only skin redness was significantly higher in the GEN group when compared to the PLA group. Following the application of the GEN product, skin hydration increased while fine pores and their area decreased. Subgroup analysis of older women (age ≥ 56 years) with adequate compliance found significant differences between the two groups in the percentage mean changes of most skin wrinkle parameters. The GEN product has benefits for the facial skin of postmenopausal women, particularly those who are older. It can moisturize facial skin, lessen wrinkles, and enhance redness.

The Development of Color Perception and Cognition

Color is a pervasive feature of our psychological experience, having a role in many aspects of human mind and behavior such as basic vision, scene perception, object recognition, aesthetics, and communication. Understanding how humans encode, perceive, talk about, and use color has been a major interdisciplinary effort. Here, we present the current state of knowledge on how color perception and cognition develop. We cover the development of various aspects of the psychological experience of color, ranging from low-level color vision to perceptual mechanisms such as color constancy to phenomena such as color naming and color preference. We also identify neurodiversity in the development of color perception and cognition and implications for clinical and educational contexts. We discuss the theoretical implications of the research for understanding mature color perception and cognition, for identifying the principles of perceptual and cognitive development, and for fostering a broader debate in the psychological sciences.

Prediction and association analyses of skin phenotypes in Japanese females using genetic, environmental, and physical features

BACKGROUND

Skin characteristics show great variation from person to person and are affected by multiple factors, including genetic, environmental, and physical factors, but details of the involvement and contributions of these factors remain unclear.

OBJECTIVES

We aimed to characterize genetic, environmental, and physical factors affecting 16 skin features by developing models to predict personal skin characteristics.

METHODS

We analyzed the associations of skin phenotypes with genetic, environmental, and physical features in 1472 Japanese females aged 20-80 years. We focused on 16 skin characteristics, including melanin, brightness/lightness, yellowness, pigmented spots, wrinkles, resilience, moisture, barrier function, texture, and sebum amount. As genetic factors, we selected 74 single-nucleotide polymorphisms of genes related to skin color, vitamin level, hormones, circulation, extracellular matrix (ECM) components and ECM-degrading enzymes, inflammation, and antioxidants. Histories of ultraviolet (UV) exposure and smoking as environmental factors and age, height, and weight as physical factors were acquired by means of a questionnaire.

RESULTS

A linear association with age was prominent for increase in the area of crow's feet, increase in number of pigmented spots, decrease in forehead sebum, and increase in VISIA wrinkle parameters. Associations were analyzed by constructing linear regression models for skin feature changes and logistic regression models to predict whether subjects show lower or higher skin measurement values in the same age groups. Multiple genetic factors, history of UV exposure and smoking, and body mass index were statistically selected for each skin characteristic. The most important association found for skin spots, such as lentigines and wrinkles, was adolescent sun exposure.

CONCLUSION

Genetic, environmental, and physical factors associated with interindividual differences of the selected skin features were identified. The developed models should be useful to predict the skin characteristics of individuals and their age-related changes.

Attractive and healthy-looking male faces do not show higher immunoreactivity

Previous research has indicated that facial attractiveness may provide cues to the functioning of the immune system. Mating with individuals who have a more effective immune system could lead to a higher reproductive success. Our main aim was to test a possible association between immunoreactivity (stimulated by vaccination) and perceived facial attractiveness and healthiness. We experimentally activated the immune system of healthy men using vaccination against hepatitis A/B and meningococcus and measured levels of specific antibodies (markers of immune system reactivity) before and 30 days after the vaccination. Further, 1 day before the vaccination, we collected their facial photographs that were judged by females for attractiveness, healthiness, and facial skin patches for healthiness. In view of its proposed connection with the functioning of the immune system, we also measured skin colouration (both from the facial photographs and in vivo using a spectrophotometer) and we assessed its role in attractiveness and healthiness judgements. Moreover, we measured the levels of steroid hormones (testosterone and cortisol) and the percentage of adipose tissue, because both are known to have immunomodulatory properties and are related to perceived facial attractiveness and healthiness. We found no significant associations between antibody levels induced by vaccination and perceived facial attractiveness, facial healthiness, or skin healthiness. We also found no significant connections between steroid hormone levels, the amount of adipose tissue, rated characteristics, and antibody levels, except for a small negative effect of cortisol levels on perceived facial healthiness. Higher forehead redness was perceived as less attractive and less healthy and higher cheek patch redness was perceived as less healthy, but no significant association was found between antibody levels and facial colouration. Overall, our results suggest that perceived facial attractiveness, healthiness, and skin patch healthiness provide limited cues to immunoreactivity, and perceived characteristics seem to be related only to cortisol levels and facial colouration.

Different colour predictions of facial preference by Caucasian and Chinese observers

Facial colour characteristics convey vital personal information and influence social interactions and mate choices as contributing factors to perceived beauty, health, and age. How various colour characteristics affect facial preference and whether there are cultural differences are not fully understood. Here, we provide a useful and repeatable methodology for skin colour research based on a realistic skin model to investigate the effect of various facial colour characteristics on facial preference and compare the role of colour predictors in Caucasian (CA) and Chinese (CN) samples. Our results show that, although the average skin colour of facial areas plays a limited role, together with colour variation and contrast, there are stronger links between colour and facial preference than previously revealed. We also find large cultural differences in facial colour perceptions; Chinese observers tend to rely more heavily on colour and lightness cues to judge facial preference than Caucasian observers.

Color Affects Recognition of Emoticon Expressions

In computer-mediated communication, emoticons are conventionally rendered in yellow. Previous studies demonstrated that colors evoke certain affective meanings, and face color modulates perceived emotion. We investigated whether color variation affects the recognition of emoticon expressions. Japanese participants were presented with emoticons depicting four basic emotions (Happy, Sad, Angry, Surprised) and a Neutral expression, each rendered in eight colors. Four conditions (E1-E4) were employed in the lab-based experiment; E5, with an additional participant sample, was an online replication of the critical E4. In E1, colored emoticons were categorized in a 5AFC task. In E2-E5, stimulus affective meaning was assessed using visual scales with anchors corresponding to each emotion. The conditions varied in stimulus arrays: E2: light gray emoticons; E3: colored circles; E4 and E5: colored emoticons. The affective meaning of Angry and Sad emoticons was found to be stronger when conferred in warm and cool colors, respectively, the pattern highly consistent between E4 and E5. The affective meaning of colored emoticons is regressed to that of achromatic expression counterparts and decontextualized color. The findings provide evidence that affective congruency of the emoticon expression and the color it is rendered in facilitates recognition of the depicted emotion, augmenting the conveyed emotional message.

Biophysical properties of redness-prone skin in Korean women

BACKGROUND

Facial skin redness can have a negative impact on the quality of life. In this study, we investigated the skin biophysical parameters associated with facial skin redness as a function of aging.

METHODS

Our aims were as follows: (1) to understand the impact of non-pathological facial skin redness on the quality of life of Korean women through a survey; and (2) compare skin biophysical properties between women with and without facial skin redness.

RESULTS

Women aged between 20 and 39 years perceived their own facial skin redness at a higher rate than those aged ≥40 years. In addition, in redness-prone women, the intensity of skin redness and skin surface perfusion were higher, while skin hydration was lower regardless of age. In redness-prone women aged ≥40 years, the values for transepidermal water loss, elasticity, and skin thickness were lower, and the mean pore depth was greater. Facial redness intensity was higher, and the distribution was wider in redness-prone younger women, while only redness intensity increased in the older age group.

CONCLUSIONS

Overall, redness-prone women aged ≥40 years had weaker skin properties. Our study indicated the age-related biophysical characteristics of non-pathological facial skin redness. We believe that our findings will help improve its negative effects.

Clothing Aesthetics: Consistent Colour Choices to Match Fair and Tanned Skin Tones

Fashion stylists advise clothing colours according to personal categories that depend on skin, hair and eye colour. These categories are not defined scientifically, and advised colours are inconsistent. Such caveats may explain the lack of formal tests of clothing colour aesthetics. We assessed whether observers preferred clothing colours that are linked to variation in melanin levels among White women. For this, we presented 12 women's faces: six with fair skin (relatively lower in melanin) and six with tanned skin (relatively higher in melanin). Across two experiments, observers (N = 96 and 75) selected the colour (hue and saturation or hue and value) of simulated clothing that most suited the skin tone of each face. Observers showed strong preferences for red and blue hues, and in addition favoured ‘cool’ blue hues to match fair skin and ‘warm’ orange/red hues to match tanned skin. This finding suggests that skin tone can determine colour preferences for clothes.

Sexual Dimorphism in Facial Contrast: A Case from Central Africa

Apart from morphological differences, male and female faces also vary in color, especially in overall lightness and facial contrast, i.e., the contrast between the luminance and color of facial features (eyes, lips, or brows) and luminance and color of the surrounding skin. In many populations, it has been demonstrated that women tend to be lighter than men. Other differences were found in facial contrast: women have a higher contrast between the lightness of their eyes and lips and the surrounding skin. Manipulation of this contrast in an artificial genderless face can result in a masculine or feminine appearance. So far, however, this phenomenon has been studied mostly in Euro-American and East Asian samples, with little evidence from populations with darker facial tone. We explored natural sexual dimorphism in both facial contrast and lightness in an African, namely Cameroonian, sample, and compared it with results for a European, in particular Czech, population. Our findings showed that sexual differences in luminance contrast of eyes and brows were in both studied populations similar but in the Cameroonian sample, significant difference in lips contrast was absent. These results indicate that sex differences in facial contrast are a side effect of the sex differences in skin color and can be used as a proxy for skin color perception.

Skin coloration is a culturally-specific cue for attractiveness, healthiness, and youthfulness in observers of Chinese and western European descent

Facial skin coloration signals information about an individual and plays an important role in social interactions and mate choice, due its putative association with health, attractiveness, and age. Whether skin coloration as an evolutionary significant cue is universal or specific to a particular culture is unclear and current evidence on the universality of skin color as a cue to health and attractiveness are equivocal. The current study used 80 calibrated, high-resolution, non-manipulated images of real human faces, either of Chinese or western European descent, which were rated in terms of attractiveness, healthiness, and perceived age by 44 observers, 22 western European (13 male; mean age ± SD = 24.27 ± 5.30) and 22 Chinese (7 male; mean age ± SD = 26.05 ± 3.96) observers. To elucidate the associations between skin coloration and these perceptual ratings and whether these associations are modulated by observer or image ethnicity, a linear mixed-effect model was setup with skin lightness (L*; CIELAB), redness (a*) and yellowness (b*), observer and image ethnicity as independent variables and perceived attractiveness, healthiness, and estimated age as dependent variables. We found robust positive associations between facial skin lightness (L*) and attractiveness, healthiness, and youthfulness, but only when Chinese observers judge facial images of their own ethnicity. Observers of European descent, on the other hand, associated an increase in yellowness(b*) with greater attractiveness and healthiness in Chinese facial images. We find no evidence that facial redness is positively associated with these attributes; instead, an increase in redness (a*) is associated with an increase in the estimated age of European facial images. We conclude that observers of both ethnicities make use of skin color and lightness to rate attractiveness, healthiness, and perceived age, but to a lesser degree than previously thought. Furthermore, these coloration cues are not universal and are utilized differently within the Chinese and western European ethnic groups. Our study adds to the growing body of work demonstrating the importance of skin color manipulations within an evolutionary meaningful parameter space, ideally using realistic skin models based on physical parameters.

Assessing the impact of aging and blood pressure on dermal microvasculature by reactive hyperemia optical coherence tomography angiography

Visualization and quantification of the skin microvasculature are important for studying the health of the human microcirculation. We correlated structural and pathophysiological changes of the dermal capillary-level microvasculature with age and blood pressure by using the reactive hyperemia optical coherence tomography angiography (RH-OCT-A) technique and evaluated both conventional OCT-A and the RH-OCT-A method as non-invasive imaging alternatives to histopathology. This observational pilot study acquired OCT-A and RH-OCT-A images of the dermal microvasculature of 13 young and 12 old healthy Caucasian female subjects. Two skin biopsies were collected per subject for histological analysis. The dermal microvasculature in OCT-A, RH-OCT-A, and histological images were automatically quantified and significant indications of vessel rarefaction in both old subjects and subjects with high blood pressure were observed by RH-OCT-A and histopathology. We showed that an increase in dermal microvasculature perfusion in response to reactive hyperemia was significantly lower in high blood pressure subjects compared to normal blood pressure subjects (117% vs. 229%). These results demonstrate that RH-OCT-A imaging holds functional information of the microvasculature with respect to physiological factors such as age and blood pressure that may help to monitor early disease progression and assess overall vascular health. Additionally, our results suggest that RH-OCT-A images may serve as a non-invasive alternative to histopathology for vascular analysis.

Skin characteristics following repeated exposure to simulated outdoor and indoor summer temperatures in South Korea and Southeast Asia

BACKGROUND

Although changes in skin depend on the external environment, researchers have performed only a few studies on effect of the actual environment. Most studies have researched skin characterization based on changes in the humidity or temperature.

AIM/OBJECTIVE

This study aimed to evaluate changes in the skin based on the difference in indoor and outdoor temperatures and humidity during summer in South Korea and Southeast Asia.

METHODS

Twenty-two female participants aged 25-39 years were included. Skin hydration, sebum (cheek, forehead), colour, transparency and pores of the participants were measured after a 30-min exposure to high temperature and high humidity (HTHH) environment and a 30-min exposure to low temperature and low humidity (LTLH) environment. Subsequently, exposure to HTHH environment for 30 min +LTLH environment for 30 min was performed after a total of 1 h and repeated.

RESULTS

Repeated exposure to HTHH and LTLH environments increased the skin's sebum content and haemoglobin index. Additionally, skin elasticity was significantly reduced, with patients in their 30 s showing greater changes than those in their 20 s.

CONCLUSION

Repeated differences in temperature and humidity cause skin ageing, loosen skin vessels and reduce skin elasticity, thereby leading to skin ageing.

Facial coloration influences social approach-avoidance through social perception

Perceptions of others' social characteristics are essential for guiding social behaviour and decision making. Recent research has demonstrated that increased facial redness facilitates both positive (e.g. health, attractiveness, happiness) and negative (e.g. dominance, anger) social evaluations. Given that similar facial colouration can lead to diverging evaluations, it is unclear how people integrate these cues to inform social decisions (e.g. approach-avoidance). We suggest that the influence of facial redness on social perceptions and decisions depends on contextual information, including facial-muscular emotion expressions. We test this hypothesis across two studies where participants view faces either increasing or decreasing redness, evaluate them on a range of social characteristics (i.e. aggressiveness, attractiveness, health, friendliness, dominance) and decide whether to approach or avoid them. Increased facial redness facilitated, and decreased redness impeded (to a greater extent), perceptions of each social characteristic. However, the extent of this influence was moderated by the muscular expression (i.e. neutral, happy, angry). Further, we found that the influence of facial redness on approach-avoidance was largely mediated by evaluations of attractiveness and health. Altogether, the current work provides nuanced insights into facial colouration's role as a social signal that informs social perception and decision making.

Female ornaments: is red skin color attractive to males and related to condition in rhesus macaques?

Sexual selection produces extravagant male traits, such as colorful ornaments, via female mate choice. More rarely, in mating systems in which males allocate mating effort between multiple females, female ornaments may evolve via male mate choice. Females of many anthropoid primates exhibit ornaments that indicate intraindividual cyclical fertility, but which have also been proposed to function as interindividual quality signals. Rhesus macaque females are one such species, exhibiting cyclical facial color variation that indicates ovulatory status, but in which the function of interindividual variation is unknown. We collected digital images of the faces of 32 rhesus macaque adult females. We assessed mating rates, and consortship by males, according to female face coloration. We also assessed whether female coloration was linked to physical (skinfold fat, body mass index) or physiological (fecal glucocorticoid metabolite [fGCM], urinary C-peptide concentrations) condition. We found that redder-faced females were mated more frequently, and consorted for longer periods by top-ranked males. Redder females had higher fGCM concentrations, perhaps related to their increased mating activity and consequent energy mobilization, and blood flow. Prior analyses have shown that female facial redness is a heritable trait, and that redder-faced females have higher annual fecundity, while other evidence suggests that color expression is likely to be a signal rather than a cue. Collectively, the available evidence suggests that female coloration has evolved at least in part via male mate choice. Its evolution as a sexually selected ornament attractive to males is probably attributable to the high female reproductive synchrony found in this species.

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.

Facial radiance influences facial attractiveness and affective impressions of faces

Objective

Facial attractiveness has been reported to be influenced by visual features such as facial shape and the colour and texture of the skin. However, no empirical studies have examined the effects of facial skin radiance on facial attractiveness. The present study investigated whether types of skin reflection (i.e. radiant, oily and shiny, and matte) and the position of the reflection on the face influence facial attractiveness and other affective impressions.

Methods

A total of 160 female participants (1) estimated the ages and (2) evaluated attractiveness and other impressions of unfamiliar female faces in a total of seven skin reflection conditions. These conditions incorporated three types of reflection (i.e. radiant, oily and shiny, and matte) and three positions of the reflection on the face (i.e. entire facial skin, only cheeks, and only T‐zone).

Results

The facial images of radiance on entire faces were rated as appearing younger than the facial images of oily shine on entire faces and the matte faces. Attractiveness ratings and other positive impressions increased in the order of the matte (ranked lowest), the oily shine on entire face, and the radiance on entire face (ranked highest) conditions. The reflection position also influenced facial attractiveness: attractiveness ratings and other positive impressions were higher in the radiance on entire face condition than in the radiant cheeks and the radiant T‐zone conditions. Interestingly, the radiant cheek faces were rated more radiant and healthier but less feminine and less bright than the radiant T‐zone faces.

Conclusion

These results suggest that facial radiance enhances facial attractiveness and conveys a wide variety of positive impressions on the observer. The magnitude of the effects of cheek radiance and T‐zone radiance differs across various affective impressions. Nevertheless, the results demonstrate that cheek and the T‐zone radiance both contribute to higher attractiveness and other positive impressions of the radiance on entire faces. We believe that our findings can contribute as a guide to the enhancement of positive facial impressions by means of skin radiance, thereby leading to a better understanding of the value of skincare and base makeup.

Feeling Stressed and Ugly? Leave the City and Visit Nature! An Experiment on Self-and Other-Perceived Stress and Attractiveness Levels

Natural environments, compared to urban environments, usually lead to reduced stress and positive body appreciation. We assumed that walks through nature and urban environments affect self- and other-perceived stress and attractiveness levels. Therefore, we collected questionnaire data and took photographs of male participants' faces before and after they took walks. In a second step, female participants rated the photographs. As expected, participants felt more restored and attractive, and less stressed after they walked in nature compared to an urban environment. A significant interaction of environment (nature, urban) and time (pre, post) indicated that the men were rated by the women as being more stressed after the urban walk. Other-rated attractiveness levels, however, were similar for both walks and time points. In sum, we showed that the rather stressful experience of a short-term urban walk mirrors in the face of men and is detectable by women.

Refined Carbohydrate Consumption and Facial Attractiveness

Since the second half of the 20th century, a massive increase in the consumption of refined carbohydrates has occurred, generating well-described detrimental health effects such as obesity, insulin resistance, type II diabetes, cardiovascular diseases and dental caries. Certain physiological mechanisms involved, particularly through chronic hyperglycaemia and hyperinsulinaemia, suggest that a non-medical trait such as facial attractiveness could also be affected. To explore this possibility, variation in facial attractiveness was evaluated relative to refined carbohydrate consumption. Attractiveness was assessed from facial pictures as judged by raters of the opposite sex. Estimates of refined carbohydrate consumption were based on the glycaemic load of three mealtimes at-higher glycaemic risk (breakfast, afternoon snack and between-meal snack). In the presence of several control variables, facial pictures of women and men with higher between-meal glycaemic loads were preferred by opposite-sex raters. Structural equation modeling suggests that this result is possibly mediated by an increase in apparent age for men and an increase in femininity for women. The different physiological ecologies of the three meals at-higher glycaemic risk are discussed as well as the interpretation of the results in terms of adaptation or maladaptation to the modern and unique dietary environment.

Skin Color Preferences in a Malaysian Chinese Population

Facial skin color influences the perceived health and attractiveness of Caucasian faces, and has been proposed as a valid cue to aspects of physiological health. Similar preferences for skin color have previously been found in African participants, while different preferences have been found among mainland Chinese participants. Here, we asked Malaysian Chinese participants (ethnic Chinese living in an Asian country with high levels of exposure to Western culture) to manipulate the skin color of Malaysian Chinese, Caucasian, and African faces to make them “look as healthy as possible.” Participants chose to increase skin yellowness to a greater extent than to increase skin redness to optimize healthy appearance. The slight reduction in skin lightness chosen was not statistically significant after correction for multiple comparisons. While broadly in line with the preferences of Caucasian and African participants from previous studies, this differs from mainland Chinese participants. There may be a role for culture in skin color preferences, though methodological differences mean that further research is necessary to identify the cause of these differences in preferences.

Social Perception of Facial Color Appearance for Human Trichromatic Versus Dichromatic Color Vision

Typical human color vision is trichromatic, on the basis that we have three distinct classes of photoreceptors. A recent evolutionary account posits that trichromacy facilitates detecting subtle skin color changes to better distinguish important social states related to proceptivity, health, and emotion in others. Across two experiments, we manipulated the facial color appearance of images consistent with a skin blood perfusion response and asked participants to evaluate the perceived attractiveness, health, and anger of the face (trichromatic condition). We additionally simulated what these faces would look like for three dichromatic conditions (protanopia, deuteranopia, tritanopia). The results demonstrated that flushed (relative to baseline) faces were perceived as more attractive, healthy, and angry in the trichromatic and tritanopia conditions, but not in the protanopia and deuteranopia conditions. The results provide empirical support for the social perception account of trichromatic color vision evolution and lead to systematic predictions of social perception based on ecological social perception theory.

Time course of the use of chromatic and achromatic facial information for sex categorization

The most useful facial features for sex categorization are the eyes, the eyebrows, and the mouth. Dupuis-Roy et al. reported a large positive correlation between the use of the mouth region and rapid correct answers [Journal of Vision 9 (2009) 1-8]. Given the chromatic information in this region, they hypothesized that the extraction of chromatic and achromatic cues may have different time courses. Here, we tested this hypothesis directly: 110 participants categorized the sex of 300 face images whose chromatic and achromatic content was partially revealed through time (200 ms) and space using randomly located spatio-temporal Gaussian apertures (i.e. the Bubbles technique). This also allowed us to directly compare, for the first time, the relative importance of chromatic and achromatic facial cues for sex categorization. Results showed that face-sex categorization relies mostly on achromatic (luminance) information concentrated in the eye and eyebrow regions, especially the left eye and eyebrow. Additional analyses indicated that chromatic information located in the mouth/philtrum region was used earlier-peaking as early as 35 ms after stimulus onset-than achromatic information in the eye regions-peaking between 165 and 176 ms after stimulus onset-as was speculated by Dupuis-Roy et al. A non-linear analysis failed to support Yip and Sinha's proposal that processing of chromatic variations can improve subsequent processing of achromatic spatial cues, possibly via surface segmentation [Perception 31 (2002) 995-1003]. Instead, we argue that the brain prioritizes chromatic information to compensate for the sluggishness of chromatic processing in early visual areas, and allow chromatic and achromatic information to reach higher-level visual areas simultaneously.

Negative Effects of Makeup Use on Perceptions of Leadership Ability Across Two Ethnicities

Cosmetics alter social perceptions, and prior work suggests that cosmetic use may aid female intrasexual competition, making women appear more dominant to other women but more prestigious to other men. It is unclear whether these findings reflect general improvements in perceptions of traits related to women’s dominance or if they are specific to mating contexts only. Here, across two ethnicities, we examined effects of cosmetics used for a social night out on perceptions of women’s leadership ability, a trait that denotes competence/high status outside of mating contexts. Participants of African and Caucasian ethnicity judged faces for leadership ability where half of the trials differed in ethnicity (own- vs. other-ethnicity face pairs) and the subtlety of the color manipulation (50% vs. 100%). Regardless of the participant’s sex or ethnicity, makeup used for a social night out had a negative effect on perceptions of women’s leadership ability. Our findings suggest that, in prior work, women are afforded traits related to dominance, as makeup enhances perceptions of traits that are important for successful female mating competition but not other components of social dominance such as leadership.

Human colour in mate choice and competition

The colour of our skin and clothing affects how others perceive us and how we behave. Human skin colour varies conspicuously with genetic ancestry, but even subtle changes in skin colour due to diet, blood oxygenation and hormone levels influence social perceptions. In this review, we describe the theoretical and empirical frameworks in which human colour is researched. We explore how subtle skin colour differences relate to judgements of health and attractiveness. Also, because humans are one of the few organisms able to manipulate their apparent colour, we review how cosmetics and clothing are implicated in courtship and competition, both inside the laboratory and in the real world. Research on human colour is in its infancy compared with human psychophysics and colour research in non-human animals, and hence we present best-practice guidelines for methods and reporting, which we hope will improve the validity and reproducibility of studies on human coloration.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.

The value of facial attractiveness for encouraging fruit and vegetable consumption: analyses from a randomized controlled trial

BACKGROUND

An effect of increased fruit and vegetable (FV) consumption on facial attractiveness has been proposed and recommended as a strategy to promote FV intakes, but no studies to date demonstrate a causal link between FV consumption and perceived attractiveness. This study investigated perceptions of attractiveness before and after the supervised consumption of 2, 5 or 8 FV portions/day for 4 weeks in 30 low FV consumers. Potential mechanisms for change via skin colour and perceived skin healthiness were also investigated.

METHODS

Faces were photographed at the start and end of the 4 week intervention in controlled conditions. Seventy-three independent individuals subsequently rated all 60 photographs in a randomized order, for facial attractiveness, facial skin yellowness, redness, healthiness, clarity, and symmetry.

RESULTS

Using clustered multiple regression, FV consumption over the previous 4 weeks had no direct effect on attractiveness, but, for female faces, some evidence was found for an indirect impact, via linear and non-linear changes in skin yellowness. Effect sizes, however, were small. No association between FV consumption and skin healthiness was found, but skin healthiness was associated with facial attractiveness.

CONCLUSIONS

Controlled and objectively measured increases in FV consumption for 4 weeks resulted indirectly in increased attractiveness in females via increases in skin yellowness, but effects are small and gradually taper as FV consumption increases. Based on the effect sizes from this study, we are hesitant to recommend the use of facial attractiveness to encourage increased FV consumption.

TRIAL REGISTRATION

Clinical trial Registration Number NCT01591057 ( www.clinicaltrials.gov ). Registered: 27th April, 2012.

Experimental evidence that primate trichromacy is well suited for detecting primate social colour signals

Primate trichromatic colour vision has been hypothesized to be well tuned for detecting variation in facial coloration, which could be due to selection on either signal wavelengths or the sensitivities of the photoreceptors themselves. We provide one of the first empirical tests of this idea by asking whether, when compared with other visual systems, the information obtained through primate trichromatic vision confers an improved ability to detect the changes in facial colour that female macaque monkeys exhibit when they are proceptive. We presented pairs of digital images of faces of the same monkey to human observers and asked them to select the proceptive face. We tested images that simulated what would be seen by common catarrhine trichromatic vision, two additional trichromatic conditions and three dichromatic conditions. Performance under conditions of common catarrhine trichromacy, and trichromacy with narrowly separated LM cone pigments (common in female platyrrhines), was better than for evenly spaced trichromacy or for any of the dichromatic conditions. These results suggest that primate trichromatic colour vision confers excellent ability to detect meaningful variation in primate face colour. This is consistent with the hypothesis that social information detection has acted on either primate signal spectral reflectance or photoreceptor spectral tuning, or both.

Color preferences in participants with high or low hypnotic susceptibility

PURPOSE

Color preferences vary among normal individuals and psychiatric patients, and this might be related to their different levels of hypnotic susceptibility. We hypothesized that individuals with higher hypnotic susceptibility prefer more arousing colors such as red.

PATIENTS AND METHODS

Out of 440 participants, we selected 70 with higher (HIGH) and 66 with lower (LOW) hypnotic susceptibilities, and asked them to undergo the Stanford Hypnotic Susceptibility Scale: Form C (SHSSC) test, then to order their preferences of 11 colors.

RESULTS

The HIGH group preferred red more and scored higher on the total SHSSC. The preference order of black was negatively predicted by the SHSSC Taste hallucination but positively by Arm rigidity, and the preference of yellow was positively predicted by Posthypnotic amnesia and Taste hallucination in the HIGH group.

CONCLUSION

The red preference and the SHSSC associations with black and yellow preferences in participants with high hypnotic susceptibility help to clarify the individual difference of color preference and provide research hints for behavioral studies in normal individuals and psychiatric patients.

Is Skin Coloration Measured by Reflectance Spectroscopy Related to Intake of Nutrient-Dense Foods? A Cross-Sectional Evaluation in Australian Young Adults

The current study examines associations between the dietary intakes of nutrient-dense foods, measured using brief indices and skin coloration, measured using reflectance spectroscopy in young adults. This is a cross-sectional analysis of 148 young Australian males and females (55% female) aged 18 to 25 years. Dietary intake was assessed using a validated food frequency questionnaire, with responses used to calculate two dietary indices: (i) the Australian Recommended Food Score (ARFS); and (ii) the Fruit And Vegetable VAriety Score (FAVVA). Skin yellowness was measured at three body locations using reflectance spectroscopy. Associations were assessed using Spearman's correlation coefficients, regression analysis, and agreement using weighted kappa (K_w). Significant, moderate correlations were found between skin yellowness and diet index scores for the ARFS (ρ = 0.30, p < 0.001) and FAVVA score (ρ = 0.39, p < 0.001). These remained significant after adjustment for confounders (total fat intake, sex, skin lightness) and for agreement based on categorical rankings. Results suggest that measurement of skin coloration by reflectance spectroscopy can be used as an indicator of overall dietary quality and variety in young adults. Further exploration in diverse populations is required.

Facial Shape Analysis Identifies Valid Cues to Aspects of Physiological Health in Caucasian, Asian, and African Populations

Facial cues contribute to attractiveness, including shape cues such as symmetry, averageness, and sexual dimorphism. These cues may represent cues to objective aspects of physiological health, thereby conferring an evolutionary advantage to individuals who find them attractive. The link between facial cues and aspects of physiological health is therefore central to evolutionary explanations of attractiveness. Previously, studies linking facial cues to aspects of physiological health have been infrequent, have had mixed results, and have tended to focus on individual facial cues in isolation. Geometric morphometric methodology (GMM) allows a bottom–up approach to identifying shape correlates of aspects of physiological health. Here, we apply GMM to facial shape data, producing models that successfully predict aspects of physiological health in 272 Asian, African, and Caucasian faces – percentage body fat (21.0% of variance explained), body mass index (BMI; 31.9%) and blood pressure (BP; 21.3%). Models successfully predict percentage body fat and blood pressure even when controlling for BMI, suggesting that they are not simply measuring body size. Predicted values of BMI and BP, but not percentage body fat, correlate with health ratings. When asked to manipulate the shape of faces along the physiological health variable axes (as determined by the models), participants reduced predicted BMI, body fat and (marginally) BP, suggesting that facial shape provides a valid cue to aspects of physiological health.