Karl Grammer

Human (Homo sapiens) facial attractiveness and sexual selection: the role of symmetry and averageness.

We hypothesized from the parasite theory of sexual selection that men (Homo sapiens) would prefer averageness and symmetry in womens faces, that women would prefer averageness and symmetry in mens faces, and that women would prefer largeness (not averageness) of the secondary sexual traits of mens faces. We generated computer images of mens and womens faces and of composites of the faces of each sex, and then had men and women rate opposite-sex faces for 4 variables (attractive, dominant, sexy, and healthy). Symmetry, averageness, and the sizes of facial features were measured on the computerized faces. The hypotheses were supported, with the exception of the hypothesized effects of averageness of female and male faces on attractiveness ratings. This is the first study to show that facial symmetry has a positive influence on facial attractiveness ratings.

Darwinian aesthetics: sexual selection and the biology of beauty

Current theoretical and empirical findings suggest that mate preferences are mainly cued on visual, vocal and chemical cues that reveal health including developmental health. Beautiful and irresistible features have evolved numerous times in plants and animals due to sexual selection, and such preferences and beauty standards provide evidence for the claim that human beauty and obsession with bodily beauty are mirrored in analogous traits and tendencies throughout the plant and animal kingdoms. Human beauty standards reflect our evolutionary distant and recent past and emphasize the role of health assessment in mate choice as reflected by analyses of the attractiveness of visual characters of the face and the body, but also of vocal and olfactory signals. Although beauty standards may vary between cultures and between times, we show in this review that the underlying selection pressures, which shaped the standards, are the same. Moreover we show that it is not the content of the standards that show evidence of convergence ‐ it is the rules or how we construct beauty ideals that have universalities across cultures. These findings have implications for medical, social and biological sciences.

Human body odour, symmetry and attractiveness

Several studies have found body and facial symmetry as well as attractiveness to be human mate choice criteria. These characteristics are presumed to signal developmental stability. Human body odour has been shown to influence female mate choice depending on the immune system, but the question of whether smell could signal general mate quality, as do other cues, was not addressed in previous studies. We compared ratings of body odour, attractiveness, and measurements of facial and body asymmetry of 16 male and 19 female subjects. Subjects wore a T–shirt for three consecutive nights under controlled conditions. Opposite–sex raters judged the odour of the T–shirts and another group evaluated portraits of the subjects for attractiveness. We measured seven bilateral traits of the subjects body to assess body asymmetry. Facial asymmetry was examined by distance measurements of portrait photographs. The results showed a significant positive correlation between facial attractiveness and sexiness of body odour for female subjects. We found positive relations between body odour and attractiveness and negative ones between smell and body asymmetry for males only if female odour raters were in the most fertile phase of their menstrual cycle. The outcomes are discussed in the light of different male and female reproductive strategies.

Individual and gender fingerprints in human body odour

Individuals are thought to have their own distinctive scent, analogous to a signature or fingerprint. To test this idea, we collected axillary sweat, urine and saliva from 197 adults from a village in the Austrian Alps, taking five sweat samples per subject over 10 weeks using a novel skin sampling device. We analysed samples using stir bar sorptive extraction in connection with thermal desorption gas chromatograph–mass spectrometry (GC–MS), and then we statistically analysed the chromatographic profiles using pattern recognition techniques. We found more volatile compounds in axillary sweat than in urine or saliva, and among these we found 373 peaks that were consistent over time (detected in four out of five samples per individual). Among these candidate compounds, we found individually distinct and reproducible GC–MS fingerprints, a reproducible difference between the sexes, and we identified the chemical structures of 44 individual and 12 gender-specific volatile compounds. These individual compounds provide candidates for major histocompatibility complex and other genetically determined odours. This is the first study on human axillary odour to sample a large number of subjects, and our findings are relevant to understanding the chemical nature of human odour, and efforts to design electronic sensors (e-nose) for biometric fingerprinting and disease diagnoses.

The Body and Face of Woman: One Ornament that Signals Quality?

Abstract Evidence has accumulated in recent years supporting the hypothesis that both facial and bodily physical attractiveness in humans are certifications of developmental and hormonal health. Such evidence indicates that physical attractiveness is an honest or Zahavian signal of phenotypic and genetic quality. The hypothesis that physical beauty connotes health was first proposed by Westermarck and was discussed later by Ellis and Symons. It has been suggested that facial attractiveness in women is a deceptive signal of youth, unrelated to phenotypic and genetic quality. This sensory-bias or super-stimulus hypothesis is not supported by this study of mens ratings of the attractiveness of photographs of 92 nude women. Independent ratings of photographs of faces, fronts with faces covered, and backs of the same women are significantly, positively correlated. The correlation between the ratings of different photos implies that womens faces and external bodies comprise a single ornament of honest mate value, apparently constructed during puberty by estrogen and also probably by developmental adaptations for symmetry. Thus, womens physical attractiveness in face and body honestly signal hormonal and perhaps developmental health.

Human (Homo sapiens) facial attractiveness in relation to skin texture and color.

The notion that surface texture may provide important information about the geometry of visible surfaces has attracted considerable attention for a long time. The present study shows that skin texture plays a significant role in the judgment of female facial beauty. Following research in clinical dermatology, the authors developed a computer program that implemented an algorithm based on co-occurrence matrices for the analysis of facial skin texture. Homogeneity and contrast features as well as color parameters were extracted out of stimulus faces. Attractiveness ratings of the images made by male participants relate positively to parameters of skin homogeneity. The authors propose that skin texture is a cue to fertility and health. In contrast to some previous studies, the authors found that dark skin, not light skin, was rated as most attractive.

A Neural Signature of Anorexia Nervosa in the Ventral Striatal Reward System

OBJECTIVE Animal studies assessing mechanisms of self-starvation under conditions of stress and diet suggest a pivotal role for the mesolimbic reward system in the maintenance of core symptoms in anorexia nervosa, which is corroborated by initial empirical evidence in human studies. The authors examined activity in the ventral striatal system in response to disease-specific stimuli in women with acute anorexia nervosa. METHOD Participants were 14 women with acute anorexia nervosa and 14 matched healthy comparison women who underwent functional magnetic resonance imaging (fMRI) during evaluation of visual stimuli depicting a female body with underweight, normal weight, and overweight canonical whole-body features according to standardized body mass indices. Participants were required to process each stimulus in a self-referring way. Ratings for each weight category were used as the control task. RESULTS Behaviorally, women with anorexia nervosa provided significantly higher positive ratings in response to underweight stimuli than in response to normal-weight stimuli, while healthy comparison women showed greater preference for normal-weight stimuli relative to underweight stimuli. Functionally, ventral striatal activity demonstrated a highly significant group-by-stimulus interaction for underweight and normal-weight stimuli. In women with anorexia nervosa, activation was higher during processing of underweight stimuli compared with normal-weight stimuli. The reverse pattern was observed in healthy comparison women. CONCLUSIONS These findings are consistent with predictions in animal studies of the pivotal role of the human reward system in anorexia nervosa and thus support theories of starvation dependence in maintenance of the disorder.

Second to fourth digit ratio and face shape

The average human male face differs from the average female face in size and shape of the jaws, cheek-bones, lips, eyes and nose. It is possible that this dimorphism is determined by sex steroids such as testosterone (T) and oestrogen (E), and several studies on the perception of such characteristics have been based on this assumption, but those studies focussed mainly on the relationship of male faces with circulating hormone levels; the corresponding biology of the female face remains mainly speculative. This paper is concerned with the relative importance of prenatal T and E levels (assessed via the 2D : 4D finger length ratio, a proxy for the ratio of T/E) and sex in the determination of facial form as characterized by 64 landmark points on facial photographs of 106 Austrians of college age. We found that (i) prenatal sex steroid ratios (in terms of 2D : 4D) and actual chromosomal sex dimorphism operate differently on faces, (ii) 2D : 4D affects male and female face shape by similar patterns, but (iii) is three times more intense in men than in women. There was no evidence that these effects were confounded by allometry or facial asymmetry. Our results suggest that studies on the perception of facial characteristics need to consider differential effects of prenatal hormone exposure and actual chromosomal gender in order to understand how characteristics have come to be rated ‘masculine’ or ‘feminine’ and the consequences of these perceptions in terms of mate preferences.

Strangers meet: Laughter and nonverbal signs of interest in opposite-sex encounters

When strangers of the opposite-sex meet for the first time, both sexes are in a difficult situation. In this high risk situation, neither person knows the intention of the other, and consequently non-verbal signalling becomes the major channel for communication. Because of their higher biological risk, females should prefer less obvious tactics in order to communicate interest in a potential partner than males. The tactical task of signalling clearly, but at the same time subtly, is solved by the use of multifunctional or metacommunicative signals. In this study we propose that there is not one single meaning for any given signal. In laughing loudly we find a signal which consists of acoustical, mimical and postural information. In this way either laughter can send a “this is play” message or its meaning can be modified by other signals. Thus laughter, together with its accompanying body postures and movements, conveys messages that range from sexual solicitation to aversion, depending on which and how many different signals are present. Males seem to communicate interest for the female during laughter with only a few signals, such as body orientation and dominance signals. In contrast, females communicate interest via numerous signals which function as signals of bodily self-presentation and submission. In both sexes, a lack of interest is communicated through closed postures.

Disco clothing, female sexual motivation, and relationship status: Is she dressed to impress?

The relationship between a females clothing choice, sexual motivation, hormone levels, and partnership status (single or not single, partner present or not present) was analyzed in 351 females attending Austrian discotheques. We digitally analyzed clothing choice to determine the amount of skin display, sheerness, and clothing tightness. Participants self‐reported sexual motivation, and we assessed estradiol and testosterone levels through saliva sampling. Results show that females are aware of the social signal function of their clothing and that they in some cases alter their clothing style to match their courtship motivation. In particular, sheer clothing—although rare in the study—positively correlated with the motivation for sex. Hormone levels influenced clothing choice in many groups, with testosterone levels correlating positively with physique display. Infernales who had a partner but were at the disco unaccompanied by the partner, estradiol levels correlated positively with skin display and clothing tightness. Significant differences were not found, however, for clothing choice across the partnership‐status groups.