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Background: Deviations of physical characteristics from bilateral symmetry, in otherwise symmetric individuals, are supposed to result from environmental perturbations during development. One cause of such perturbations may be sex steroids such as testosterone and oestrogen. Aim: The study examined the relationship between second to fourth digit ratio (2D:4D), a putative negative correlate with prenatal testosterone and a positive correlate with prenatal oestrogen, and asymmetry. Methods: Eleven traits (including the second and fourth finger lengths) were measured in a sample of 680 English children aged 2–18 years, and second to fifth finger lengths in samples of 120 Austrian and English undergraduate students aged from 17 to 30 years and 213 Polish adults aged from 26 to 90 years. Results: Significant U-shaped curvilinear associations between 2D:4D and all 11 traits were found in English children with the strongest associations between 2D:4D and composite asymmetry of second plus fourth digit, and second to fifth digits. Further investigation of the relation between 2D:4D and digit asymmetries in the sample of Austrian and English undergraduates and the Polish adults confirmed significant U-shaped relationships between 2D:4D and finger asymmetries. Conclusion: Our data show that both low 2D:4D (a marker of high prenatal testosterone) and high 2D:4D (a marker of high prenatal oestrogen) are associated with elevated levels of asymmetry and this relationship applies particularly to finger asymmetry.

Individuals with body modifications, such as tattoos, have been shown to differ from nonmodified individuals in sensation-seeking personality characteristics and sociosexuality. This study examined possible differences in people’s attributions of those characteristics toward virtual human characters varying in body modification. Some 287 participants rated tattooed and nontattooed bodies of avatars on aspects of sensation seeking and number of previous sexual partners. Tattooed stimuli were rated as more experience, thrill, and adventure seeking as well as more likely to have a high number of previous sexual partners and as less inhibited when compared to nontattooed stimuli, and this was particularly true for male stimuli. It was concluded that people with body modifications, such as tattoos, are perceived differently compared to nontattooed individuals in terms of sensation seeking and previous sexual partner number, this being particularly true for men. Findings are discussed with reference to the evolutionary model of human sexual selection.

Sex steroids have important influences upon brain development and this may lead to sex differences in developmental psychopathology. Digit ratio (2D:4D) – a negative correlate of prenatal testosterone (T) – may provide further insight into the possible role of early organizational effects on such developmental psychopathology. We measured 2D:4D ratios in a group of schoolchildren in two countries (UK and Austria) and gave questionnaires assessing behavioural problems to their parents. Although there were few differences in behavioural measures between sexes (only the externalizing behaviour score was higher in Austrian boys), several correlations existed between 2D:4D and different indices of developmental psychopathology. Low 2D:4D (indicating higher prenatal T) was related to measures of total difficulties and poor conduct in both UK and Austrian children. In the UK sample, prosocial behaviour was positively related to 2D:4D in girls and hyperactivity and conduct correlated negatively with 2D:4D in boys. Associations were generally stronger for boys than for girls. We suggest that early androgen mediation effects during prenatal development increase the probability for gender-related behaviour problems.

Animals often use acoustical cues, such as formant frequencies, to assess the size of potential mates and rivals. Reliable vocal cues to size may be under sexual selection. In most mammals and many other vertebrates, formants scale with vocal tract length allometrically and predict variation in size more reliably than fundamental frequency or pitch (F0). In humans, however, it is unclear from previous work how well voice parameters predict body size independently of age and sex. We conducted a meta-analysis to establish the strength of various voice–size relationships in adult men and women. We computed mean weighted correlations from 295 coefficients derived from 39 independent samples across five continents, including several novel and large cross-cultural samples from previously unpublished data. Where possible, we controlled for sample size, sample sex, mean age, geographical location, study year, speech type and measurement method, and ruled out publication bias. Eleven of 12 formant-based vocal tract length (VTL) estimates predicted men's and women's heights and weights significantly better than did F0. Individual VTL estimates explained up to 10% of the variance in height and weight, whereas F0 explained less than 2% and correlated only weakly with size within sexes. Statistically reliable size estimates from F0 required large samples of at least 618 men and 2140 women, whereas formant-based size estimates required samples of at least 99 men and 164 women. The strength of voice–size relationships varied by sample size, and in some cases sex, but was largely unaffected by other demographic and methodological variables. We confirm here that, analogous to many other vertebrates, formants provide the most reliable vocal cue to size in humans. This finding has important implications for honest signalling theory and the capacity for human listeners to estimate size from the voice.

Male movements serve as courtship signals in many animal species, and may honestly reflect the genotypic and/or phenotypic quality of the individual. Attractive human dance moves, particularly those of males, have been reported to show associations with measures of physical strength, prenatal androgenization and symmetry. Here we use advanced three-dimensional motion-capture technology to identify possible biomechanical differences between women’s perceptions of ‘good’ and ‘bad’ male dancers. Nineteen males were recorded using the ‘Vicon’ motion-capture system while dancing to a basic rhythm; controlled stimuli in the form of avatars were then created in the form of 15 s video clips, and rated by 39 females for dance quality. Initial analyses showed that 11 movement variables were significantly positively correlated with perceived dance quality. Linear regression subsequently revealed that three movement measures were key predictors of dance quality; these were variability and amplitude of movements of the neck and trunk, and speed of movements of the right knee. In summary, we have identified specific movements within men’s dance that influence women’s perceptions of dancing ability. We suggest that such movements may form honest signals of male quality in terms of health, vigour or strength, though this remains to be confirmed.

The ratio of 2nd to 4th digit length (2D:4D), the systemizing quotient (SQ) and the empathizing quotient (EQ) are putative correlates of prenatal testosterone. However, the evidence that 2D:4D is related to SQ or EQ is mixed. Voracek and Dressler (2006) used indirect finger measurements and found no significant associations with 2D:4D and SQ or EQ, whereas von Horn, Bäckman, Davidsson, and Hansen (2010) reported significant correlations between 2D:4D and a composite measure of SQ and EQ using direct finger measurements. Here we report associations of 2D:4D, SQ and EQ in participants from a large internet survey in which direct measurements of fingers were collected. We found (i) significant negative correlations of SQ with 2D:4D, this being stronger for right hand 2D:4D and independent of sex, age, height, ethnicity, sexual orientation, and education, (ii) no significant correlation of EQ and 2D:4D. We further examined mean 2D:4D’s and found suggestions of a distortional effect of indirect finger measurement in the Voracek and Dressler (2006) study. Our results partly replicate those of von Horn et al. (2010) and emphasize the use of direct finger measurements when studying associations between 2D:4D and target traits with small effect size.

Recent research has revealed that variation in human dancing ability is related to levels of fluctuating asymmetry, and that women rate symmetrical male dancers more positively. We measured the lengths of the 2nd (index) and 4th (ring) finger in a sample of young men and recorded short digital video clips of their dance movements. A panel of 104 female judges rated 12 clips of men with the lowest and highest finger-length ratios (2D:4D) for attractiveness, dominance, and masculinity. We found that dances by men with low (masculinised) 2D:4D ratios were rated significantly higher on attractiveness, dominance, and masculinity than dancers with high (feminised) 2D:4D. There were no significant differences between the two groups of dancers for age and other physical measures such as waist-to-hip ratio (WHR) and body-mass-index (BMI). Since there is evidence that finger-length ratios negatively correlate with testosterone exposure in utero, male dancing abilities may be organized early during development. Moreover, women’s ability to perceive differences in dance movement of men with low and high 2D:4D may indicate that dance provides some cues to phenotypic condition, relevant for sexual selection.

It is taken for granted that the non-verbal information we acquire from a person's body posture and position affects our perception of others. However, to date human postures have never been described on an empirical level. This study is the first approach to tackle the unexplored topic of human postures. We combined two approaches: traditional behavior observation and modern anthropometric analysis. Photographs of 100 participants were taken, their body postures were transferred to a three dimensional virutal environment and the occurring body angles were measured. The participants were asked to fill in a questionnaire about their current affective state. A principal component analysis with the items of the affect questionnaire (Positive Negative, Affect Scales, PANAS) revealed five main factors: aversion, openness, irritation, happiness, and self-confidence. The body angles were then regressed on these factors and the respective postures were reconstructed within a virtual environment. 50 different subjects rated the reconstructed postures from the positive and negative end of the regression. We found the ratings to be valid and accurate in respect to the five factors.

  Objectives: Age at menarche (AAM) in the general population may be influenced by prenatal sex steroids. The ratio of the second and fourth digits (2D:4D) is a putative correlate of prenatal sex steroids, but the relationship of 2D:4D to AAM is controversial. Matchock ([2008]: Am J Hum Biol 20:487-489) has reported that right 2D:4D (but not left) was negatively related to AAM, but Helle ([2010a]: Am J Hum Biol 22:418-420) found no relationship. Here the association between 2D:4D, AAM, and self-reported rate of pubertal development (RPD) is considered. Methods: The sample consisted of self-measured finger lengths and AAM and RPD reported by women in the BBC internet study. Results: There were 70,658 white women who reported a mean (± SD) AAM of 12.54 (1.48) years. Right 2D:4D was negatively related to AAM and positively related to RPD. These relationships were independent of left 2D:4D, age and height. Between-country variation in right 2D:4D was also significantly related to AAM such that in countries with low 2D:4D women mean AAM was higher. Conclusions: In support of the findings of Matchock, right 2D:4D was found to be negatively related to AAM. In addition, right 2D:4D was positively related to RPD. In a sample of 19 countries, mean right 2D:4D was negatively correlated with mean national AAM. These findings suggest that women with high prenatal testosterone and low prenatal estrogen tend to show late menarche and slow pubertal development.

Objectives: Recent research suggests that evolutionary selection pressures have shaped mental mechanisms to be able to assess one's own and other's physical strength, fighting ability, and aggressiveness. According to the recalibrational theory, anger may be linked to fighting ability and serve as a bargaining mechanism to improve welfare obtained in social conflict. We hypothesized that late adolescent men (but not mid-adolescent men or women) use this mechanism, as it would be particularly adaptive for them to avoid potential costs from direct conflict in male competition. Methods: The present study investigated the relationship between fighting ability (estimated from handgrip strength [HGS], a measure of upper body strength, and self-reported fighting ability) and aggressiveness (physical and nonphysical) in 288 Spanish adolescents aged 14–18 years. Results: Our results indicated a positive relationship between self-perceived fighting ability and HGS in both sexes during adolescence. There was no association between fighting ability and aggressiveness in late adolescent women (17–18 years). For men, there was a positive relationship between fighting ability and physical aggression, but the strength of this relationship decreased with age. Additionally, for men, there was a positive relationship between fighting ability and anger but only in late adolescence, and thus arguing that for adolescent men aggression strategies shift from physical to nonphysical as they age.   Conclusions: With reference to the recalibrational theory of anger, our results suggest that the sex- and age-dependent associations between fighting ability and physical and nonphysical aggression indicate divergent adaptive skills between sexes, which are driven by intrasexual competition.

The ratio between the 2nd and 4th fingers (2D:4D)—a potential proxy for prenatal testosterone (T) exposure—shows a sex difference, with males usually having lower mean values; the latter potentially indicates higher prenatal T exposure. We studied relations between 2D:4D and competencies in the domains of counting, number knowledge, and visual-number representation in 73 children aged 6–11 years. Significant negative correlations between numerical performance in all of these areas and right and left hand 2D:4D ratios were found for boys but not girls. To the extent that 2D:4D ratios reflects prenatal exposure to T, the implications are (i) high prenatal T may be associated with better performance on some basic numerical measures for boys, and (ii) prenatal exposure to T may affect boys and girls differently with respect to some numerical competencies.

Evolutionary theory proposes that adaptive traits are reproduced more successfully than maladaptive traits. Accordingly, natural selection should favour heterosexuality as it facilitates reproduction and the propagation of genes. However, the question becomes, what has maintained homosexuality in a small but consistent percentage of the human population? Research into the evolutionary and hormonal factors associated with a homosexual orientation have yielded provocative but inconsistent results. It also suggests that human sexual orientation, and in particular homosexual orientation, is too complex to be described by one simple model or a single research discipline. The current paper treads a new path and emphasises an integrative approach for the understanding of homosexuality. The authors examine the combined effects of evolutionary factors and neurohormonal processes on the development of a homosexual orientation. It is suggested that research into the topic could benefit from an examination of and change in some of the assumptions upon which much past research has been based.

Recent evidence suggests that the concept of ‘concealed ovulation’ in women should be reconsidered, as there appear to be certain behavioural, visual, olfactory, and vocal cues that serve as indirect cues to female fertility. Here we test the hypothesis that men are able to discern fertile from non-fertile women based on their dance and gait movements. Digital videos of dances and gaits of 48 heterosexual women, aged 19–33 years, were recorded twice, once in the late follicular phase, and once in the mid-luteal phase of their menstrual cycle. Short video clips comprising movement silhouettes of dances and gaits were judged on attractiveness by a total of 200 men. Dances and gaits recorded in the late follicular were rated significantly more attractive compared to recordings in the mid-luteal phase. We suggest that (i) menstrual cycle effects on women’s body movements exist, and (ii) men are sensitive to these effects, as they expressed a stronger preference (via attractiveness judgments) for women’s body movements at times of peak fertility. Our data add body movements to the list of features that show systematic changes across the menstrual cycle and support the assertion that men are able to detect cues of female fertility.

Objectives  Evolutionary psychology suggests that a woman’s age and physical appearance are important mate choice criteria. Given that changes in female facial skin surface topography are important, prominent visible signs of aging, male perceptual sensitivity for variation in this trait may also affect preference and attractiveness judgment. Methods  Two experiments were conducted to investigate perception (Experiment 1) and noticeability (Experiment 2) of skin surface topography manipulations in facial images of six British women, aged 45–65 years. In Experiment 1 skin surface topography cues were completely removed on the cheeks, the “crow’s feet” area adjacent to the eye, under the eyes, above the upper lip, and on the forehead while, in Experiment 2, it was removed gradually (20% increments) on the forehead and around the eyes. In both experiments, stimuli were presented to American and German participants (total N = 300, aged 15–55 years) in omnibus pair-wise combinations (within-face). With each pair, respondents were asked to select that face which they considered as younger looking (Experiments 1 and 2) and more attractive (Experiment 1). Results  Faces with skin surface topography cues removed were judged significantly younger and more attractive than their original (unmodified) counterparts, with modifications on the forehead and around the eyes showing the highest differences. In these areas, participants were able to detect at least a 20% visual change in skin surface topography. Conclusions  The results support the assertion that even small changes in skin surface topography affect the perceptions of a woman’s facial age and attractiveness and may, thus, also influence men’s mate preferences.

Risk-taking behaviour in men, an expression of the more general personality trait sensation seeking, has been hypothesized to be an evolved aspect of male psychology that arose through sexual selection. Sensation seeking could be seen as a costly behavioural trait that signals a man’s health and vigour and is preferred by women. This study extends knowledge about risk-taking as a cue in human mate choice by examining whether women can perceive men’s sensation seeking propensity (assessed with the Sensation Seeking Scale Form V; SSS-V) by viewing their dance movements. We videotaped 50 men’s dancing and had 60 women judge each dancer on perceived attractiveness and risk-taking. A positive and significant correlation was found between women’s attractiveness judgements and male’s SSS-V total score, thrill and adventure seeking, disinhibition and boredom susceptibility. Further, women’s risk-taking judgements were related to men’s boredom susceptibility. We conclude that (i) male sensation seeking propensity is signalled via their dance movements, and (ii) women are sensitive to these cues as they consider men who score high on sensation seeking as attractive. We discuss our results with reference to the evolutionary psychology concept of sexual selection and mate preferences.

Although there is evidence that perception of facial age, health and attractiveness is informed by shape characteristics as well as by visible skin condition, studies on the latter have focused almost exclusively on female skin. Recent research, however, suggests that a decrease in skin colour homogeneity leads to older, less healthy and less attractive ratings of facial skin in both women and men. Here, we elaborate on the significance of the homogeneity of visible skin colouration in men by testing the hypothesis that perception of age, health and attractiveness of (non-contextual) digitally isolated fields of cheek skin only can predict that of whole facial images. Facial digital images of 160 British men (all Caucasian) aged between 10 and 70 were blind-rated for age, health and attractiveness by a total of 147 men and 154 women (mean age = 22.95, SD = 4.26), and these ratings were related to those of corresponding images of cheek skin reported by Fink et al. (J. Eur. Acad. Dermatol. Venereol. in press). Linear regression analysis showed that age, health and attractiveness perception of men’s faces could be predicted by the ratings of cheek skin only, such that older men were viewed as older, less healthy and less attractive. This result underlines once again the potent signalling role of skin in its own right, independent of shape or other factors and suggests strongly that visible skin condition, and skin colour homogeneity in particular, plays a significant role in the perception of men’s faces.

The purpose of this study was to consider relationships between digit ratio (2D:4D, a putative correlate of prenatal sex steroids) and aggregate personality scores across nations. Differences in national personality scores may be influenced by such factors as prevalence of the parasite Toxoplasma gondii, latitude and economics, and variation in 2D:4D has also been linked to prevalence of T. gondii and to latitude. Here we report associations of mean 2D:4D per country and latitude, gross domestic product (GDP), T. gondii prevalence and personality profiles in 23 nations of an internet study. 2D:4D was not related to latitude or to T. gondii, but was related to GDP (women only). With regard to national personality scores, 2D:4D was not related to masculinity but there were significant positive relationships of 2D:4D with uncertainty avoidance in men and women and with neuroticism in men. Male 2D:4D was significantly related to uncertainty avoidance and neuroticism independent of T. gondii, whereas female 2D:4D was not significantly related to uncertainty avoidance or neuroticism after controlling for the effect of T. gondii and GDP. We conclude that nations with high male 2D:4D (low prenatal testosterone, high prenatal oestrogen) have high scores for uncertainty avoidance and neuroticism.

The Compatibility Quotient (CQ) is an index of similarity within established or potential couples across a variety of domains known to predict long-term relationship success. Validation data has been presented showing that established couples have substantially higher CQ scores than randomly paired couples and that couples with rewarding relationships have higher CQs than those whose relationship is less happy. Here we show that CQ scores predict desire to pursue a relationship after only a brief speed-date encounter. Nineteen young men had 3-minute social exchanges with 19 young women, providing data on 361 potential relationships. Those couplings in which both parties expressed a desire at least for friendship showed mean CQs of 107.7, compared with a mean of 102.7 for couplings in which at least one party had no desire for further contact (p < 0.001). The CQ was also predictive of immediate physical attraction. Mutually attracted couples averaged CQs of 108.0 compared with 101.2 for those not attracted to each other (p < 0.01). These effects were apparently driven by female preferences, with males being less discriminating.

The proportion of women (PW) across occupations shows considerable variation. Here we hypothesize that occupational segregation could be moderated by the effect of testosterone (T), leading individuals to gender-typical choice of occupation. To test this, we examined the relationship between PW across 22 occupations and three putative correlates of T (the 2nd to 4th digit ratio [2D:4D], a supposed correlate of prenatal T [PT]; body height, a possible correlate of adult T [AT]; and a systemizing–empathizing score [SQ–EQ], a putative behavioural correlate of PT and AT) in a large internet survey. PW varied from 17% (Engineering/R&D) to 94% (Homemaker) per occupation. Compared to participants in female-typical jobs, participants in male-typical jobs tended to have low right hand 2D:4D and low right–left hand 2D:4D [Dr-l] (higher PT, women only), were taller (higher AT, men and women), and had higher SQ–EQ scores (higher PT and AT, men and women). With regard to women, the relationships for Dr-l and SQ–EQ (but not body height) remained significant when Whites only were considered. We conclude that in women Dr-l, and SQ–EQ are related to occupational segregation, suggesting that high PT and AT are found in women who are in male-typical occupations.

Deviations from perfect symmetry in paired traits of otherwise bilateral symmetrical organisms are thought to reflect developmental quality, especially the ability to resist environmental perturbations early in ontogeny. It is well established that poor environmental conditions increase developmental instability (DI) as reflected by measurements of fluctuating asymmetry. In humans, there is evidence that DI relates to numerous fitness components, and studies have found that perceptions of facial attractiveness for example are positively correlated with measurements of facial symmetry. Here we report the data on measurements of facial symmetry of 503 Turkish senior year high school students aged 17 to 18 years, of whom 133 males and 117 females were recruited from a slum district of Şentepe in Ankara (Group 1), and 131 males and 122 females from three high schools in wealthy central urban areas (Group 2). Digital images were used to assess the degree of facial asymmetry as measured from seven paired traits and calculated as a composite score. Facial asymmetry of participants in Group 1 (slum district) was significantly higher than that of participants in Group 2 (urban areas). Moreover, males in Group 1 were found to have higher facial asymmetry than females, while no sex difference was observed in Group 2. We conclude that poor living conditions have an influence on DI in humans, which manifests itself in the form of facial asymmetry, and that this might be particularly true for males.