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Background: The ratio of the lengths of the 2nd and 4th digit (2D:4D) is negatively related to prenatal and adult concentrations of testosterone (T). Testosterone appears to be a protective against myocardial infarction (MI) in men as men with low 2D:4D are older at first MI than men with high 2D:4D, and men with coronary artery disease have lower T levels than men with normal angiograms. Neck circumference (NC), a simple and time-saving screening measure to identify obesity is reported to be positively correlated with the factors of the metabolic syndrome, a complex breakdown of normal physiology characterized by obesity, insulin resistance, hyperlipidemia, and hypertension, and is therefore likely to increase the risk of coronary heart disease (CHD). Objective: To investigate possible associations between 2D:4D ratios and NC in men and women. Research methods and procedures: 2D:4D ratios, NC, along with measures of waist and hip circumferences, body mass index (BMI), and waist-to-hip ratio was recorded from 127 men and 117 women. Results: A significant positive correlation between 2D:4D and NC and was found for men but not for women after controlling for body mass index (BMI); the higher the ratio the higher the NC. Discussion: This finding supports the suggestion of NC to serve as a predictor for increased risk for CHD as previously suggested. In addition, the present association suggests a predisposition for men towards CHD via 2D:4D as proxy to early sex-steroid exposure.
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Several studies have demonstrated that the ratio between the lengths of the second and fourth digits (2D:4D) is sexually dimorphic. On average males demonstrate lower digit ratios than do females. There is accumulating evidence that 2D:4D is established early in development and is negatively related to prenatal testosterone and positively with prenatal estrogen. In this present study, we investigated associations between digit ratio and the ‘big-five’ personality factors (extraversion, neuroticism, openness, conscientiousness and agreeableness). Only agreeableness showed a significant sex difference with females scoring higher. Neuroticism showed a significant positive correlation with right hand digit ratio for the whole sample, and in females only for right hand 2D:4D. Further, a significant negative association was found between females’ right hand digit ratio and agreeableness. Male 2D:4D did not correlate significantly with any of the personality factors. The results follow previous studies reporting that 2D:4D was a stronger correlate of personality traits in females than in males. In summary, the associations between digit ratio and personality factors are weak but provide some further support for the claim that gender-related behaviour is affected by the amount of steroid hormones present during critical periods of prenatal development.
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Facial expressions of emotions are important in nonverbal communication. Although numerous neural structures have been identified to be involved in emotional face processing, the amygdala is thought to be a core moderator. While previous studies have relied on facial images of humans, the present study is concerned with the effect of computer-generated (avatar) emotional faces on amygdala activation. Moreover, elicited activation patterns in response to viewing avatar faces are compared with the neuronal responses to human facial expressions of emotions. Twelve healthy subjects (five females) performed facial emotion recognition tasks with optimized 3T event-related fMRI. Robust amygdala activation was apparent in response to both human and avatar emotional faces, but the response was significantly stronger to human faces in face-sensitive structures, i.e. fusiform gyri. We suggest that avatars could be a useful tool in neuroimaging studies of facial expression processing because they elicit amygdala activation similarly to human faces, yet have the advantage of being highly manipulable and fully controllable. However, the finding of differences between human and avatar faces in face-sensitive regions indicates the presence of mechanisms by which human brains can differentiate between them. This mechanism merits further investigation.
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The effect of sensory input on hormones is essential to any explanation of mammalian behavior, including aspects of physical attraction. The chemical signals we send have direct and developmental effects on hormone levels in other people. Since we don't know either if, or how, visual cues might have direct and developmental effects on hormone levels in other people, the biological basis for the development of visually perceived human physical attraction is currently somewhat questionable. In contrast, the biological basis for the development of physical attraction based on chemical signals is well detailed.
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Digit ratio (2D:4D) may be a correlate of prenatal sex steroids, and has been linked to traits, which are influenced by fetal testosterone and estrogen. Here we consider such links in a large Internet study of sex differences (the BBC Internet Study) in which finger lengths were self-measured. Consistent with lab-based findings the 2D:4D in this study shows sexual dimorphism, ethnic differences and higher dimorphism of right 2D:4D than left, thereby indicating that 2D:4D does measure real between-participant variation. High error in self-measurement of fingers reduces effect sizes. However, the large sample size gives assurance that significant effects are likely to be real. We controlled for ethnicity and sexual orientation by considering White heterosexuals only (153,429 participants). Sexual dimorphism was confirmed in 2D:4D and for the difference of right–left 2D:4D. After Bonferroni correction we found highly significant relationships with low effect sizes as follows. In males and females there were negative associations between 2D:4D and dominance. In males there were negative associations between 2D:4D and family size and factors associated with reproductive success. For females these associations were positive. For asymmetry we found U-shaped relationships with 2D:4D in both males and females. We found no relationship between 2D:4D and promiscuity (sociosexuality). In total, we considered 48 relationships and found 29 to be significant. We compare our findings with a similar study reported by Putz et al. (2004), which found only 2 out of 57 correlations to be significant and discuss possible reasons for the discrepancies between the studies.
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Bilateral symmetry of physical traits is thought to reflect an individual’s phenotypic quality, especially their ability to resist environmental perturbations during development. Therefore, facial symmetry may signal the ability of an individual to cope with the challenges of their environment. Studies concerning the relationship between symmetry and attractiveness lead to the conclusion that preferences for symmetric faces may have some adaptive value. We hypothesized that if symmetry is indeed indicative of an individual’s overall quality, faces high in symmetry should receive higher ratings of attractiveness and health, but also be perceived as demonstrating certain positive personality attributes. College students’ attributions of a set of 20 female faces varying in facial symmetry were recorded. As predicted, faces high in symmetry received significantly higher ratings of attractiveness, health, and certain personality attributes (i.e., sociable, intelligent, lively, self-confident, balanced). Faces low in symmetry were rated as being more anxious. These differences were not caused by an attractiveness stereotype. The present results lend further support to the notions that (i) facial symmetry is perceived as being attractive, presumably reflecting health certification and (ii) people also consider facial symmetry as a cue to an individuals’ quality with regard to certain personality characteristics.
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Background: Prenatal sex steroids have been broadly discussed in terms of their possible effect on brain differentiation, whereas pubertal/adult sex hormones are thought to be the main regulators of sexually dimorphic physical features in males and females. Assessing prenatal steroid exposure has previously been difficult but evidence now suggests that finger length ratio may provide a ‘window’ into prenatal hormone exposure. The length of the second digit (the index finger) relative to the length of the fourth digit (the ring finger) is sexually dimorphic as males have a lower second to fourth digit ratio (2D:4D). The sexual dimorphism is determined as early as the 14th week of fetal life, and remains unchanged at puberty. There is evidence that sex differences in 2D:4D arise from in utero concentrations of sex steroids, with a low 2D:4D (male typical ratio) being positively related to prenatal testosterone, while a high 2D:4D (female typical ratio) is positively associated with prenatal oestrogen. Aim: The studied aimed to determine whether, and to what extent, adult sexually dimorphic physical traits, which are largely determined at puberty, relate to traits that are largely determined in utero. This work examined the relationship between three sexually dimorphic traits—body mass index (BMI), waist-to-hip ratio (WHR) and waist-to-chest ratio (WCR)—and digit ratio. Participants and methods: BMI, WHR and WCR were assessed in 30 heterosexual male and 50 heterosexual female participants by recording their body height, weight, and measuring their waist, hip and chest circumference. Digit lengths of the second and fourth fingers were measured from photocopies of the ventral surface of the hand and by actual finger measurements. Results: Digit ratio was found to be significantly lower in men than in women. Significant negative correlations were found between female’s left and right hand 2D:4D, waist and hip circumference, and WCR. In males, BMI was found to be positively related to digit ratio but remained significant only for left hand 2D:4D. Generally, the relationships were stronger for females than for males. Although not all relationships were found to be significant, they were in accord with our predictions. Conclusion: In addition to an activational effect of sex hormones at puberty, the present data suggest an early organizational effect of sex hormones through the association between indices of female body shape, male BMI, and human finger length patterns.
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In this work, we provide evidence based on direct observation of behavior in encounters of opposite-sexed strangers, that women initiate and “control” the outcome. In the first minute of these videotaped 10-min interactions, neither female “solicitation” behavior nor “negative” behavior is strongly related to professed interest in the man, while female “affirmative” behavior at this stage modulates male verbal output in later stages (4–10 min). Although the rate of female courtship-like behavior is significantly higher in the first minute, it is only in the fourth to tenth minute that the rate of female courtship-like behavior is correlated with professed female interest. We hypothesize that this serves as a strategic dynamic reflecting sexual asymmetry in parental investment and the potential cost of male deception to women. Ambiguous protean behavioral strategies veil individuals' intentions and make their future actions unpredictable. These behavioral strategies may result in men's overestimation of female sexual interest.
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The ratio of the length of the second and fourth digits (2D:4D), a putative proxy of prenatal testosterone (PT), is correlated with measures of physical fitness. The relationship between the organizing effect of PT on physical fitness is likely to arise as a response to intrasexual male competition for females. Physical strength is also likely to be important in intrasexual conflict, but nothing is known concerning the relationship between 2D:4D and strength. The strength of an individual is strongly influenced by body size, and 2D:4D is strongly dependent on ethnicity. We present evidence that strength, as measured from hand-grip strength, is related to 2D:4D in samples from two ethnic groups (52 Caucasian men from Germany, and 88 Oriental Mizos men from northeast India) which differed markedly in size. We found that 1) the German men were heavier and stronger, but had higher 2D:4D (lower PT) than the Mizos men; 2) a median split for grip strength into low (LGS) and high (HGS) groups showed that for right-hand 2D:4D (but not left-hand 2D:4D), the LGS men had higher 2D:4D than the HGS men; and 3) the relationships between right 2D:4D and grip strength were independent of ethnicity, age, height, and weight. Measures of grip strength correlate strongly with strength in other muscle groups, so we conclude that PT may have an early organizing effect on strength in men, and this is likely to be widespread in human groups.
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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.
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Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. This ratio is considered to be a biomarker of the balance between fetal testosterone (T) and estrogen (E) in a narrow window of early ontogeny. Evidence for this assertion is derived from direct and indirect measures of prenatal hormonal exposure (in experimental animals, via amniotic fluid samples and in the study of sex-typical traits) in relation to 2D:4D. In contrast, the relationships between 2D:4D and levels of sex steroids in adults are less clear, as many correlational studies of 2D:4D and adult sex steroids have concluded that this association is statistically non-significant. Here, we suggest that in order to understand the link between 2D:4D and sex hormones, one must consider both fetal organizing and adult activating effects of T and E. In particular, we hypothesize that 2D:4D correlates with organizing effects on the endocrine system that moderate activating effects in adulthood. We argue that this is particularly evident in “challenging” conditions such as aggressive and sexual encounters, in which individuals show increased levels of T. We discuss this refinement of the 2D:4D paradigm in relation to the links between 2D:4D and sports performance, and aggression.
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Human physical attractiveness is supposed to reflect developmental stability (i.e. the ability of individuals to maintain stable development of their morphology under a given environmental condition) and physiological status. Hence, evolutionary psychologists have suggested that appearance may not only reveal so called ‘honest signals’ but even comprise a single ornament of mate value. However, it is still a matter of debate which physical features affect the ratings of female beauty, and whether these features are truly associated with aspects of developmental and physiological status. Here we present morphometric data of images of faces and bodies from 92 women together with ratings of attractiveness by 60 men. A total of 101 somatometric landmarks were digitized as two-dimensional coordinates from three views: facial, front and back full-body view. These image sets were analyzed separately by means of geometric morphometric methodology (GMM). Attractiveness ratings of the face and body were significantly associated with both (i) the amount of fluctuating asymmetry (as a measure of developmental stability), and (ii) specific localized shape differences in regions of known estrogen sens itivity. The results support the notion that ratings of women’s physical attractiveness are indeed based on indicators of developmental stability and physiological status.
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In contemporary Western populations, some physical characteristics are sexually dimorphic, and it is known that these traits also affect human mate preferences. Height is one such characteristic, and evidence suggests that females prefer taller over shorter males, indeed, taller males have been found to have greater reproductive success. However, relative height is also important with ‘Sexual Dimorphism in Stature’ (SDS) calculated as male height/female height. Pawlowski (2003) showed that people adjust their preferences for SDS in relation to their own height in order to increase their potential pool of partners. The aim of the present study was to replicate Pawlowski’s study on a larger sample of participants, and to investigate the universality of the reported preference adjustment within European societies. We present data of 1102 men and women from three countries (Germany, Austria, and the UK) that confirm Pawlowski’s original data on a Polish sample. Moreover, the mechanism of an adjustment of SDS preferences in relation to own height was found in all three countries, suggesting that height dependent partner preference is a genuine feature in Western societies.
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The present study investigated possible associations between facial symmetry and actual personality as assessed by the ‘big-five’ personality factors: neuroticism (N), extraversion (E), openness (O), agreeableness (A), and conscientiousness (C). Digital photographs were taken of male and female faces, volunteers also completed the NEO-FFI personality inventory. Facial images were analysed for horizontal symmetry by means of digital image processing. Following previous reports we predicted that facial symmetry should be negatively related to neuroticism but positively related to extraversion, openness, agreeableness, and conscientiousness. In general, our data on actual personality confirmed previous reports on perceptions of personality for neuroticism and extraversion. Neuroticism was found to be negatively but not significantly related to facial symmetry whereas extraversion was positively associated. In contrast to previous data, we found significant negative associations between facial symmetry and openness and agreeableness. Conscientiousness was non-significantly related to facial symmetry. The strongest associations with facial symmetry were found for extraversion and openness. Our results suggest that behavioural perceptions of an individual may reflect an individual’s actual personality, and facial symmetry is a correlate of personality. However, because of some inconsistencies between this and previous studies we suggest that (1) the associations between facial symmetry and personality traits require further investigation, and (2) future studies should urge for methodological consistency to make results comparable.
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It was once widely believed that standards of beauty were arbitrarily variable. Recent research suggests, however, that people's views of facial attractiveness are remarkably consistent, regardless of race, nationality or age. Facial characteristics are known to influence human attractiveness judgements and evolutionary psychologists suggest that these characteristics all pertain to health, leading to the conclusion that humans have evolved to view certain bodily features as attractive because the features were displayed by healthy others. Here we review some of the fundamental principles of sexual selection theory that apply to human beauty and summarize the major findings of human beauty perception.
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Objectives: Evolutionary psychologists claim that women have adaptive preferences for specific male physical traits. Physical strength may be one of those traits, because recent research suggests that women rate faces of physically strong men as more masculine, dominant, and attractive. Yet, previous research has been limited in its ability to statistically map specific male facial shapes and features to corresponding physical measures (e.g., strength) and ratings (e.g., attractiveness). Methods: The association of handgrip strength (together with measures of shoulder width, body height, and body fat) and women's ratings of male faces (concerning dominance, masculinity, and attractiveness) were studied in a sample of 26 Caucasian men (aged 18–32 years). Geometric morphometrics was used to statistically assess the covariation of male facial shape with these measures. Statistical results were visualized with thin-plate spline deformation grids along with image unwarping and image averaging. Results: Handgrip strength together with shoulder width, body fat, dominance, and masculinity loaded positively on the first dimension of covariation with facial shape (explaining 72.6%, P < 0.05). These measures were related to rounder faces with wider eyebrows and a prominent jaw outline while highly attractive and taller men had longer, narrower jaws and wider/fuller lips. Conclusions: Male physical strength was more strongly associated with changes in face shape that relate to perceived masculinity and dominance than to attractiveness. Our study adds to the growing evidence that attractiveness and dominance/masculinity may reflect different aspects of male mate quality.
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Sensation seeking has been described as a trait referring to the tendency to seek novel, varied, complex, and intense sensations and experiences; and the willingness to take risks for the sake of such experiences. Explanations for sensation seeking have been based upon genetic, evolutionary, psychophysiological, and sociocultural models. This study further examines the possibility that prenatal hormones – as measured via 2D:4D finger length ratio – may influence the development of certain personality characteristics associated with sensation seeking ( Austin, Manning, McInroy, & Mathews, 2002 ). We studied the relationship between 2D:4D ratios, a supposed proxy for prenatal testosterone (T), and sensation seeking as assessed by the Sensation Seeking Scale Form V (SSS-V) in a sample of 278 German and UK University students. There were significant sex differences for 2D:4D and on the SSS-V, with males having lower 2D:4D ratios, but higher SSS-V scores. Furthermore, right- and left-hand 2D:4D in males was significantly negatively associated with total sensation seeking score, and the boredom subscale. No significant associations were found for women. Since low 2D:4D is supposed to indicate exposure to higher levels of T in utero, our data suggest that there may be an organizational effect of T which influences later development of sensation seeking personality characteristics in men.
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Several studies have reported a positive association between degree of facial symmetry and attractiveness ratings, although the actual causes of the development of facial asymmetries remains to be confirmed. The current study hypothesizes that early hormone levels may play a crucial role in the development of facial asymmetries. Recent evidence suggests that the relative length of the second to fourth finger (2D:4D) is negatively related to prenatal testosterone and positively related to prenatal estrogen and may thus serve as a window to the prenatal hormonal environment. We measured 2D:4D in a sample of male and female college students and analysed their faces for horizontal asymmetries. 2D:4D was significantly negatively related to facial asymmetry in males, whereas in females facial asymmetry was significantly positively related to 2D:4D. We suggest that digit ratio may thus be considered as a pointer to an individual's developmental instability and stress through its association with prenatal sexual steroids.
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Prenatal exposure to testosterone is thought to promote the development of the right-hemisphere and increase the incidence of sinistrality. A direct test of this hypothesis has previously been problematic because of the difficulty of indirectly assessing prenatal sex steroid exposure. Evidence now suggests that the ratio between the length of the second and fourth digits (2D:4D) is related to prenatal testosterone exposure. We tested whether digit ratio is related to the degree of hand skill such that low 2D:4D (indicating high levels of testosterone in utero) may be correlated with enhanced left-hand performance. In right-handed children, high 2D:4D correlated with improved right-hand skill and low 2D:4D correlated with enhanced left-hand skill. Correlations were found to be similar for girls and for boys. Since low 2D:4D has been previously reported to be associated with faster left-hand speed compared to right in Afro-Caribbean children with very low mean 2D:4D, the present finding in a Caucasian population with high mean 2D:4D suggests that a tendency of improved left-hand performance due to prenatal testosterone may be found across ethnic groups.
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Objective: Body dissatisfaction is of high prevalence among women all over the Western world. It is often suggested that sociocultural processes are the main cause of such widespread dissatisfaction. Here, we consider how perceptual effects may influence ideas of body normality and body ideals. Method: Women who varied on a measure of body dissatisfaction rated a range of bodies for how normal and ideal they looked. They were exposed to either thin or fat bodies, and then they rerated the bodies. Results: Women's perceptions of body normality and ideal were easily malleable by exposure. In addition, greater body dissatisfaction and internalization of the thin Western ideal were related to (i) a smaller most normal and ideal body, (ii) a greater discrepancy between the most normal and most ideal-rated body, and (iii) a reduced effect of exposure to fat bodies. Discussion: Reduced updating of perceptions of body normality and body ideals in response to experience may be one mechanism that maintains body dissatisfaction.
