Digit Ratio

The ratio of the second and fourth digits of the human hand (2D:4D ratio) is an indirect measure of pre-10 natal exposure to testosterone, with a lower ratio indicating higher exposure . Based on a 11 previous report by that women with low 2D:4D ratios were more likely to describe them-12 selves as assertive, we examined the correlation between 2D:4D ratio and score on the Rathus Assertiveness 13 Schedule (RAS, Rathus, 1973). While ) depended on self-reports of finger length and used a 14 chi-square analysis that did not quite reach statistical significance, we measured finger length from photo-15 copied hands and used a parametric statistical analysis by the Pearson product correlation coefficient. 16

Males tend to be more aggressive than females and the organizational effects of prenatal testosterone (T) appear to contribute to this sex difference. Low second-to-fourth digit ratio (2D:4D) is thought to be a marker of high prenatal testosterone. For this reason, a number of studies have used 2D:4D to investigate a potential effect of prenatal T upon aggression in later life. Here we meta-analyse these studies to determine the true size of the relationship between 2D:4D and aggression. We find no evidence of 2D:4D better predicting aggression at different levels of risk nor do we find evidence for a relationship between 2D:4D and aggression in females. Regarding males we find some evidence of a small, negative relationship between 2D:4D and aggression (r % À.06) and no indication that either hand would predict aggression better than the other. We contrast these findings with results regarding levels of aggression in females with elevated prenatal T levels due to Congenital Adrenal Hyperplasia and we discuss implications for 2D:4D research.

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 bodymass-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.

Background: Digit ratios, such as the second to fourth digit ratio (2D:4D), are biometric markers that are influenced by estrogen and testosterone concentrations in utero and are determined genetically by HOX genes (homeodomain-containing homeotic genes). Sex steroids also play a crucial role in the occurrence of myocardial infarction (MI), which is considered to be gender dependent and related to testosterone. Additionally, first-trimester exposure to excess levels of estrogens and progesterone has been linked to cardiovascular anomalies. Objective: The aim of this work was to study digit ratios in a Greek population and assess their clinical importance as markers of predisposition to MI. Methods: Two samples were used: a group of Greek men and women hospitalized with MI, and a control group of healthy Greek men and women of the same age. Finger lengths were measured twice for both hands using electronic calipers. In the results, digits were designated as 2D (second digit), 3D (third digit), 4D (fourth digit), and 5D (fifth digit). Results: A total of 50 Greek men and 50 Greek women with MI were recruited (mean [SD] age, 69.3 [11.2] years for men; 69.7 [11.0] years for women). The control group consisted of 40 healthy Greek men and 40 healthy Greek women (mean age, 68.0 [11.8] years for men; 66.8 [10.7] years for women). In the control group, 2D:4D, 2D:3D, and 2D:5D ratios were significantly higher in women than in men (2D:4D: right hand, P < 0.001; left hand, P = 0.002; 2D:3D: right hand, P < 0.001; left hand, P = 0.003; 2D:5D: right hand, P < 0.001; left hand, P < 0.05). The mean values of 2D:4D ratios appeared to increase in the following order: healthy men < men with MI < healthy women < women with MI, although this difference was not statistically significant. In men with MI, 2D:4D and 3D:4D ratios were significantly higher than the respective ratios in healthy men (2D:4D: right hand, P = 0.001; left hand, P < 0.05; 3D:4D: right hand, P < 0.05; left hand, P = 0.001), but no significant differences were observed in the ratios between women with MI and healthy women. Conclusions: Digit ratios that include ring-finger length (ie, 4D) may be useful biomarkers for predisposition to MI in Greek men, but not in Greek women. Sexual dimorphism of digit ratios was present in both groups and was independent of the individuals' health status. (Gend Med. 2010;7:628–636)

Men and women differ statistically in the relative lengths of their index and ring fingers; and the ratio of these lengths has been used as a biomarker for prenatal testosterone. The ratio has been correlated with a wide range of traits and conditions including prostate cancer, obesity, autism, ADHD, and sexual orientation. In a genome-wide association study of 979 healthy adults, we find that digit ratio is strongly associated with variation upstream of SMOC1 (rs4902759: P = 1.41 9 10 -8 ) and a meta-analysis of this and an independent study shows a probability of P = 1.5 9 10 -11 . The protein encoded by SMOC1 has recently been shown to play a critical role in limb development; its expression in prostate tissue is dependent on sex hormones, and it has been implicated in the sexually dimorphic development of the gonads. We put forward the hypothesis that SMOC1 provides a link between prenatal hormone exposure and digit ratio.

This study was conducted on children and adolescents from the three tribal cultures from Northern Tanzania: the Hadza, the Datoga and the Iraqw. The comparative data on aggression and conflict management skills were measured at Endomaga Boarding School, Lake Eyasi, Mangola in Northern Tanzania, in 2005-2006. The final sample included 219 children, ranging from 7 to 20 years of age. No sex differences were found in self-ratings or frequency of occurrence of physical, verbal and indirect aggression in Iraqw children and adolescents, or in self-ratings in Hadza. Hadza boys reported a higher occurrence of physical and indirect aggression during the previous week compared to girls. No differences between the sexes were found in constructive conflict resolution and third-party interventions practiced by Iraqw and Datoga children and self-ratings in Hadza. Hadza boys reported a higher frequency of constructive conflict resolution and third-party interventions compared to girls. Significant sexual dimorphism on the 2D:4D ratio was found for our African sample. A significant negative correlation between the right hand 2D:4D ratio and ratings on physical aggression was found for the girls. The girls with the lowest finger index estimated themselves as more verbally aggressive, compared to girls with a medium 2D:4D ratio. KEYWORDS Gender (sex) differences; physical aggression; verbal aggression; indirect aggression; constructive conflict resolution; third-party intervention; consolation; socialisation strategies; 2D:4D ratio. correlates with indirect aggression after age 12. The period between the ages of 11 and 15 is marked by rapid physiological and mental development. At this time, adolescents acquire major social skills and competence in social interactions with their peers, which are critical for social success in adulthood.

We analyzed sex differences in spatial and recall abilities of college students while also examining the relationship to 2D:4D ratio. The 2D:4D ratio is thought to be an indirect measure of testosterone and estrogen exposure in fetal development. Participants completed a mental rotation (MR) test, free recall tests, and placement recall tests. It was predicted and confirmed that males have lower 2D:4D ratio and higher MR scores. Additionally, females outscored males on picture free recall and picture placement. Higher scoring females on these two measures had higher 2D:4D ratios, that is, more ''feminine'' looking hands. The results from our study are consistent with the hypothesis that fetal hormones affect 2D:4D ratio while also directly or indirectly influencing visual recall abilities in females. The tendency of sexually dimorphic cognitive skills to correlate with 2D:4D ratio in only one sex may be typical of traits that were evolutionarily adaptive in one sex, but not maladaptive in the opposite sex.

The 2nd to 4th digit ratio (2D:4D) is a sexually dimorphic biometric marker, related to prenatal estrogen and testosterone levels in utero, and determined genetically by the HOX genes. 2D:4D presents a population variation, which seems to be dependent on geographical position or ethnicity, and may reflect differences in prenatal steroid hormone levels among different ethnic groups. In view of its clinical importance, this study investigates the 2D:4D ratio, as well as other digit ratios, in Greek population. A sample of 60 Greek men and 60 Greek women (age range 19-25 years) was selected by random procedures. Fingers&#39; length was measured twice, using an electronic vernier calliper (precision 0.01 mm). Men had lower 2D:4D ratio (0.974 +/- 0.035 for the right hand and 0.973 +/- 0.044 for the left hand) than women (1.002 +/- 0.04 for the right hand and 1.001 +/- 0.045 for the left hand). This difference in 2D:4D ratio between sexes was statistically significant (p &lt; 0.0001 for t...

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.

Sexual differentiation leads to the development of
distinctive anatomical structures (e.g., gonads and genitalia);
it also produces less obvious anatomical shifts in brain, bones,
muscles, etc. This study is a retrospective analysis of growth
patterns in the hands in relation to sex and sexual orientation.
Using data from three published studies, we analyzed four
hand traits in adults: hand width, hand length, second digit
length, and fourth digit length. Using these measurements,we
derived estimates of trait laterality (directional asymmetry or
DA) and developmental instability (fluctuating asymmetry or
FA). High FA is a putative indicator of interference with the
cellular and molecular mechanisms regulating development.
We focused on how these derived variables were related to
sex, sexual orientation, and putative markers of early sex
steroid exposure (e.g., the second to fourth digit ratio or
2D:4D). Our data point to three principal conclusions. First,
individual differences in DA appeared to be a major source of
variation in the 2D:4Dratio. The 2D:4Dratios of heterosexual
men differed depending on whether they had leftward or
rightward DA in their digits. Homosexual women showed the
same pattern. Individuals with leftward DA in both digits had
lower 2D:4D ratios than those with rightward DA. This effect
was absent in heterosexualwomen and homosexualmen. This
led to sex differences in 2D:4D and sexual orientation differences
in 2D:4D in the leftward DA group, but not in the
rightward DA group. The second conclusion was that DA in
digit length and hand width varied with sex; women were
more likely to have rightward asymmetry than men. Homosexual
men and womenwere generally sex typical inDA. The
third conclusion was that homosexuality is unlikely to be a
result of increased developmental instability. Although limited
in scope, the present evidence actually suggests that
homosexuals have lower FA than heterosexuals, raising the
question of whether the positive fitness components associated
with low FA may contribute to selection that maintains
homosexuality in a population.

This  paper  presents  some  preliminary  findings  from Wave  7  of  the  Innovation  Panel  (IP7)  of Understanding  Society:  The  UK  Household  Longitudinal  Study.  Understanding  Society  is  a major panel survey in the UK. In June 2014, the seventh wave of the Innovation Panel went into the field. IP7 includes a new refreshment sample and used a mixed-mode design, using on-line interviews and face-to-face interviews. This paper describes the design of IP7, the experiments carried and the preliminary findings from early analysis of the data.

Objectives:Our aims are, first, to describe the sex difference in the length ratio of the second and fourth digits (2D:4D), which likely reflects prenatal testosterone levels in humans. Second, to infer the loss of reliability observed in 2D:4D based on self-measured finger lengths.Our aims are, first, to describe the sex difference in the length ratio of the second and fourth digits (2D:4D), which likely reflects prenatal testosterone levels in humans. Second, to infer the loss of reliability observed in 2D:4D based on self-measured finger lengths.Methods:We used random-effects meta-analysis of 2D:4D based on expert-measured finger lengths (116 samples with 13,260 females and 11,789 males).We used random-effects meta-analysis of 2D:4D based on expert-measured finger lengths (116 samples with 13,260 females and 11,789 males).Results:We find a moderate sex difference (with lower 2D:4D for males), which shows substantial heterogeneity (which is unrelated to age). The sex difference is moderated by the type of finger length measurement and by hand. Measurement involving the distortion of soft tissue leads to a significantly larger sex difference than finger length measurement avoiding this. The sex difference in 2D:4D is larger in the right hand than in the left. The reliability of self-measured 2D:4D in the BBC internet study, by far the largest study on 2D:4D, is estimated to be 46% of that of expert-measured 2D:4D.We find a moderate sex difference (with lower 2D:4D for males), which shows substantial heterogeneity (which is unrelated to age). The sex difference is moderated by the type of finger length measurement and by hand. Measurement involving the distortion of soft tissue leads to a significantly larger sex difference than finger length measurement avoiding this. The sex difference in 2D:4D is larger in the right hand than in the left. The reliability of self-measured 2D:4D in the BBC internet study, by far the largest study on 2D:4D, is estimated to be 46% of that of expert-measured 2D:4D.Conclusions:Right-hand 2D:4D might be a better indicator of prenatal androgenisation than left-hand 2D:4D. The view that 2D:4D has allometric properties (Kratochvil L, Flegr J. 2009. Differences in 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line. Biol Lett 5:643–646.) is not supported. Bone lengths contribute to the sex difference in 2D:4D. In addition, there might be a sex difference in fingers' soft tissue, which should be investigated. Because of measurement unreliability, correlations between 2D:4D and variables of interest are about one-third smaller in the BBC internet study than in studies in which 2D:4D is based on expert-measured finger lengths. Am. J. Hum. Biol. 22:619–630, 2010. © 2010 Wiley-Liss, Inc.Right-hand 2D:4D might be a better indicator of prenatal androgenisation than left-hand 2D:4D. The view that 2D:4D has allometric properties (Kratochvil L, Flegr J. 2009. Differences in 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line. Biol Lett 5:643–646.) is not supported. Bone lengths contribute to the sex difference in 2D:4D. In addition, there might be a sex difference in fingers' soft tissue, which should be investigated. Because of measurement unreliability, correlations between 2D:4D and variables of interest are about one-third smaller in the BBC internet study than in studies in which 2D:4D is based on expert-measured finger lengths. Am. J. Hum. Biol. 22:619–630, 2010. © 2010 Wiley-Liss, Inc.

Digit ratio (2D:4D) is a negative correlate of prenatal testosterone. The current study tested the hypothesis that 2D:4D would be associated with the type of military service chosen by young Korean males. Our sample consisted of 128 young males aged 22-26 years (M = 24.32, SD = 0.89). We measured the 2D:4D on the participants' right hands and explored its relationship to their selection of one of four branches of military service. Statistical analysis found no significant differences among the four branches of military service but supported our hypothesis of significant group differences in 2D:4D between Marines and all non-Marines. As expected, members of the Marine Corps demonstrated the lowest digit ratios, whereas those in the Army showed the highest. The average 2D:4D was 0.94 (SD = 0.05) for the Marine Corps, 0.95 (SD = 0.07) for the Air Force, 0.96 (SD = 0.06) for the Navy, and 0.97 (SD = 0.06) for the Army. Our research found evidence of small but significant group differences in 2D:4D among members of different branches of military service. We conclude that low 2D:4D is related to the risk and severity associated with the type of military training selected by recruits.

Intersexual and intrasexual variation in second to fourth digit length (2D:4D) in humans may result from differential exposure to fetal testosterone. 2D:4D predicts several physiological, psychological and performance traits in adulthood. These relationships may reflect the 'pleiotropic' effects of testosterone on development of digits and diverse organ systems, which are expressed in adulthood. We hypothesized that 2D:4D also predicts academic success of students. 2D:4D of right hand positively predicted examination marks of males from two threeyear degree courses (TYDCs). Marks of females did not covary with 2D:4D. Males from the two TYDCs differed in 2D:4D. The present results thus add to the rapidly accumulating literature on 2D:4D showing correlations with phenotypic traits in humans. If testosterone affects 2D:4D and intellectual performance, our results suggest that testosterone levels are under stabilizing selection because of effects on performance traits documented in previous studies and antagonistic effects on intellectual performance (present study).

Digit ratio (2D:4D) is a putative marker of prenatal hormone exposure. A lower digit ratio has been suggested as an index of higher testosterone relative to estrogen exposure during prenatal development. Digit ratio has been associated with a variety of psychological sex-dimorphic variables, including spatial orientation, aggression, or risk-taking behavior. The present study aimed to relate digit ratio to traffic violations for a male sample (N = 77) of frequent car drivers. Digit ratio was assessed via printout scans of the hand, and traffic offense behavior was assessed via self-reported penalty points as registered by the Central Register of Traffic Offenders in Germany. In addition, social desirability and sensation seeking were recorded. Results showed that digit ratio was inversely related to penalty point entries, suggesting more traffic violations for individuals with higher prenatal testosterone exposure. Sensation seeking was positively associated with traffic violations, but there was no relationship between sensation seeking and digit ratio, proposing additive effects of both variables. The results suggest that prenatal androgen exposure might be related to traffic violations for frequent car drivers.

Digit ratio (2D:4D) is a sexually dimorphic trait. Men have relatively shorter index fingers (2D) compared to ring fingers (4D) than women. Evidence suggests that more masculine ratios are influenced by higher prenatal testosterone levels. Testosterone and aggression are related and accordingly evidence suggests that male 2D:4D is related to physical aggression and female 2D:4D is related to reactive aggression . As it has been shown that violent media have an impact on aggressive behavior, we predict that the relationship between 2D:4D and aggression should be stronger when exposed to an aggressive than to a non-aggressive music video. Accordingly, we show that 2D:4D and aggression (as measured by two different measures) are related, but only after exposure to the aggressive video. We suggest that future 2D:4D research should focus on plausible interactions between 2D:4D and context cues rather than on linear relations.

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

Recently, a number of authors have claimed that sexual dimorphism in the second-to-fourth digit ratio (2D:4D) is simply dependent on digit length and is an artifact of allometry. The goal of our study is to verify the validity of these assumptions. The study sample comprised 7,582 individuals (3,802 men and 3,780 women) from three large world populations: Europeans (n = 3043), East Africans (n = 2844), and Central Asians (n = 1695). The lengths of the second and fourth digits on both hands were measured. Digit ratios were computed according to standard procedures. Analyses were conducted separately for each hand for the whole sample and in succession for the three large populations. Additionally, we separately tested four age cohorts (≤ 13, 14–18, 19–30, and 31 ≥ years) to test the effect of developmental allometry. The second and fourth digits showed strong positive linear relationships on both hands, and demonstrated an increase with age; digit length in women from the youngest ag...

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 Ôbig-fiveÕ 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 femalesÕ 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.

The feminist movement purports to improve conditions for women, and yet only a minority of women in modern societies self-identify as feminists. This is known as the feminist paradox. It has been suggested that feminists exhibit both physiological and psychological characteristics associated with heightened masculinization, which may predispose women for heightened competitiveness, sex-atypical behaviors, and belief in the interchangeability of sex roles. If feminist activists, i.e., those that manufacture the public image of feminism, are indeed masculinized relative to women in general, this might explain why the views and preferences of these two groups are at variance with each other. We measured the 2D:4D digit ratios (collected from both hands) and a personality trait known as dominance (measured with the Directiveness scale) in a sample of women attending a feminist conference. The sample exhibited significantly more masculine 2D:4D and higher dominance ratings than comparison samples representative of women in general, and these variables were furthermore positively correlated for both hands.The feminist paradox might thus to some extent be explained by biological differences between women in general and the activist women who formulate the feminist agenda.

There is sex-difference in humans as regards aerobic efficiency, physical strength and endurance and the sex difference is greatly dependent upon differential concentration of testosterone during different phases of growth and development including the intrauterine phase or prenatal growth. Second-to-fourth digit lengths ratio (2D:4D) is an putative indicator of prenatal testosterone exposure. Lower 2D:4D indicates higher prenatal testosterone exposure and vice versa. Males generally have lower 2D:4D than females. This cross-sectional study investigated the relationship between the fitness measures and 2D:4D in young adult Polish males. The study included 118 Polish male students first course in General Kościuszko Military Academy of Land Forces in Wroclaw. Their mean (+SD) age was 20.4 (+1.60) years. Eurofit test set was employed to assess physical fitness. Apart from height, weight, second and fourth digit lengths, hand grip strength was also measured by a standard isometric dynamometer. The study showed a weak relationship between 2D:4D of right hand and results of physical fitness tests. The smaller was the 2D:4D, the better was the result of endurance and strength tests. This finding was in accord with reports by other studies, indicating that individuals with smaller 2D:4D tend to perform better in these aspects of physical ability. However, we also found an opposite relationship with the results to agility tests. Male students with higher 2D:4D scored better in 5x10 meters shuttle run. This finding did not match with results reported by other studies. This study indicated towards possibility that an association between low 2D:4D and sport and athletic achievement and also physical performances were due to, at least in part, the action of prenatal testosterone. Further studies are required to investigate the relationship of fitness parameters with digit ratio and ultimately with prenatal testosterone exposure.
Key words: Eurofit test, 2D:4D, digit ratio, testosterone, male, Poland

The ratio between 2nd and 4th digit length (2D: 4D) may be a negative correlate of prenatal testosterone. This possibility has led to a number of studies of 2D: 4D and its relationship with sexual orientation and other sex-dependent traits. At first, 2D: 4D ratio was calculated from measurements made directly on the fingers but recently a number of studies have used measurements from photocopies of the hands. Here, we compared finger lengths (2D, 3D, 4D, and 5D) and ratios obtained from these two measurement techniques. Our sample ...

The ratio of second to fourth digit length (2D:4D) is a correlate of prenatal testosterone. High 2D:4D is associated with low prenatal testosterone, and reduced sensitivity to testosterone. Klinefelter's syndrome (KS; 47 XXY) affects the endocrine system, such that low testosterone levels are found in KS foetuses, new-borns and adults. To date, there are no published data regarding the pattern of 2D:4D in KS males. Here we consider 2D:4D in KS individuals (n = 51), their relatives (16 fathers and 15 mothers) and an unaffected control sample of 153 men and 153 women. Adult KS individuals were taller than their fathers and had shorter fingers than fathers and male controls. Compared with fathers, male controls and mothers, KS males had shorter fingers relative to height. With regard to 2D:4D, KS individuals had higher 2D:4D than fathers (right and left hands), male controls (right and left hands) and mothers (left hands). Among KS males older than 13 years there were 34 individuals currently prescribed testosterone and nine not prescribed. In comparison to the former, the latter individuals had higher right 2D:4D and higher right-left 2D:4D. We conclude that KS males have mean 2D:4D values similar to those found in female population norms. In addition, testosterone supplementation in KS males may be most common for individuals with low right 2D:4D.

Sexual dimorphism in digit length ratios is well established in humans, and has been reported in other vertebrate species as well, including birds. The sign of sexual dimorphism in digit ratios may, however, vary both within and between vertebrate classes. It has been hypothesized that sex differences in digit ratios arise via differential prenatal exposure of the two sexes to steroids, which may affect the expression of the Hox genes controlling the osteometric development of digits and appendices. Among birds, the evidence for sex dimorphism in hind-limb digit ratios is conflicting, though all previous studies were based on measurements of undissected digits, implying that results could be confounded by sex-related variation in soft tissues. Here we report that digit ratios derived from radiographs of both feet of a large passerine bird, the hooded crow (Corvus corone), are sexually dimorphic, males showing larger 2D : 3D (effect size, r = 0.33) and 2D : 4D than females (effect size, r = 0.28). We also observed a good agreement (r = 0.45) between radiographic estimates of digit ratios and digit ratios calculated based on undissected digit measurements (thus including soft tissues). Importantly, we found that the patterns of sex and side differences were largely coherent between the two methods. Therefore, our findings show for the first time in avian species that sex differences in digit ratios have an osteometric basis, a fundamental prerequisite for a role of Hox genes in originating such dimorphism.

We measured the second to fourth (2D:4D) digit ratio in participants who carried out a phonological task (memory for word order) and a spatial task (mental rotation). We also assessed hand preference and determined the relative skill of their left and right hands. Regression analyses showed that the difference between the 2D:4D ratio on the left and right hands (Dr-l), was a significant predictor of performance on the memory for word order task. Handedness was a significant predictor of unique variance only if Dr-l was excluded from the regression analyses. Performance on the mental rotation task was not predicted either by handedness, 2D:4D or Dr-l. The findings are discussed in terms of a possible differential effect of sex hormones on the two cerebral hemispheres.

The hand metrics of Palaeolithic artists show a number of distinctive features that contrast with the low variance hand metrics of modern Europeans, and with the majority of other modern humans. For example, the D2/D4 ratio in the Palaeolithic artists has a much greater spread of values and a greater degree of sexual dimorphism. We find that living San people, who represent the minority of modern humans that have high-variance genetics, also have a hand metric phenotype like the Palaeolithic artists, different from modern Europeans and other low-variance genetics modern humans. The increased variance and sexual dimorphism of the phenotypic D2/D4 ratio in the San measurements are in keeping with genetic evidence that the San represent one of the oldest human lineages with the greatest genetic diversity. The findings have the implication that the European Palaeolithic cave artists may have been derived from San-like migrants who brought an established artistic tradition from Africa to Europe, only to be replaced as a population, leaving no evidence of their genetics in modern Europeans, as observed for other Palaeolithic genes such as Oase 1.

It has been suggested that prenatal testosterone (PT) is positively related to intelligence or learning-ability skills. Digit ratio (2D:4D) is a negative correlate of PT. This study considered the correlations between 2D:4D and success in practical and theoretical examinations in the Dental School curriculum of a Brazilian University. Overall, 80 subjects (40 males) had their right hand palm photographed by a digital camera attached to a standardising device. The index and ring fingers were measured using Adobe Photoshop. Digit ratio was correlated to the grades obtained by the students through four semesters. Theoretical and practical grades were significantly negatively correlated to digit ratio in males (and this was particularly so after the influence of age and hours of study were removed, p = 0.02 and 0.004, respectively), but not in females (p = 0.89 and 0.77, respectively). This finding supports a link between high PT and intelligence in males. Our finding of no relationship between 2D:4D and examination marks in female students, suggests that PT may not influence intelligence in females.

The 2nd to 4th digit ratio (2D:4D) is a sexually dimorphic biometric marker, related to prenatal estrogen and testosterone levels in utero, and determined genetically by the HOX genes. 2D:4D presents a population variation, which seems to be dependent on geographical position or ethnicity, and may reflect differences in prenatal steroid hormone levels among different ethnic groups. In view of its clinical importance, this study investigates the 2D:4D ratio, as well as other digit ratios, in Greek population. A sample of 60 Greek men and 60 Greek women (age range 19-25 years) was selected by random procedures. Fingers&#39; length was measured twice, using an electronic vernier calliper (precision 0.01 mm). Men had lower 2D:4D ratio (0.974 +/- 0.035 for the right hand and 0.973 +/- 0.044 for the left hand) than women (1.002 +/- 0.04 for the right hand and 1.001 +/- 0.045 for the left hand). This difference in 2D:4D ratio between sexes was statistically significant (p &lt; 0.0001 for t...

The ratio of second to fourth digit (2D4D) has been shown to correlate negatively with entrepreneurial skills and financial success. We document that in a sample of entrepreneurs women have a lower 2D4D ratio than men, in sharp contrast with the features of the distribution in random samples. Exploiting variation across communities in indices correlated with women emancipation, we show that in regions where women are less emancipated their average DR is lower than that of men compared to regions with higher indices. This finding is consistent with the existence of gender related obstacles into entrepreneurship so that only women with well above average entrepreneurial skills find it attractive to self-select into entrepreneurship. This finding can rationalize three facts: a) fewer women than men are entrepreneurs; b) the proportion of women among entrepreneurs tends to be higher in countries with higher women emancipation; c) women who break the barrier into entrepreneurship seem to show more masculine traits. We also find that once women enter entrepreneurship, they are equally able than man to translate their ability into outcomes for the firm.

The feminist movement purports to improve conditions for women, and yet only a minority of women in modern societies self-identify as feminists. This is known as the feminist paradox. It has been suggested that feminists exhibit both physiological and psychological characteristics associated with heightened masculinization, which may predispose women for heightened competitiveness, sex-atypical behaviors, and belief in the interchangeability of sex roles. If feminist activists, i.e., those that manufacture the public image of feminism, are indeed masculinized relative to women in general, this might explain why the views and preferences of these two groups are at variance with each other. We measured the 2D:4D digit ratios (collected from both hands) and a personality trait known as dominance (measured with the Directiveness scale) in a sample of women attending a feminist conference. The sample exhibited significantly more masculine 2D:4D and higher dominance ratings than compariso...

Digit ratio (2D:4D) is a biomarker for prenatal hormonal exposure. Some studies suggest that prenatal hormonal exposure might influence our cognitive styles characterized by systemizing and empathizing tendencies while other studies do not support these findings. By assessing 156 university students of engineering or mathematics (science, technology, engineering, and mathematics (STEM) (female: 63 and male 93) we concluded that digit ratio may support the hypothesis on sexual differences in cognitive styles.

Although an indicator of prenatal testosterone (PT), 2D:4D ratio, has been extensively studied in the domain of financial risk taking, other domains of risk have received less attention. It is thought that elevated levels of PT relate to more masculinised behaviours, including increased risk taking propensity. In this study, we report negative findings with regards to health (average weekly drinking and daily smoking) and sexual (lifetime number of sexual partners) risk in a sample of post-menopausal Finnish women (N = 146-262). Our results suggest that PT may not masculinise health and sexual risk taking in women, at least at an older age.

A B S T R A C T The 2 nd to 4 th digit ratio (2D:4D) is a sexually dimorphic biometric marker, related to prenatal estrogen and testoster-one levels in utero, and determined genetically by the HOX genes. 2D:4D presents a population variation, which seems to be dependent on geographical position or ethnicity, and may reflect differences in prenatal steroid hormone levels among different ethnic groups. In view of its clinical importance, this study investigates the 2D:4D ratio, as well as other digit ratios, in Greek population. A sample of 60 Greek men and 60 Greek women (age range 19 – 25 years) was selected by random procedures. Fingers' length was measured twice, using an electronic vernier calliper (precision 0.01 mm). All participating persons gave their consent to the study, which was approved by the Faculty Ethics Committee. Individuals with former hand lesions, endocrinopathies and chromosomal abnormalities were excluded from the study. Bio-statistical analysis was performed using the statistical package SPSS. Men had lower 2D:4D ratio (0.974 ± 0.035 for the right hand and 0.973 ± 0.044 for the left hand) than women (1.002 ± 0.04 for the right hand and 1.001 ± 0.045 for the left hand). This difference in 2D:4D ratio between sexes was statistically significant (P<0.0001 for the right hand and P<0.001 for the left hand). The other digit ratios were also lower in men than women for both hands; this difference was statistically significant for all digit ratios of the right hand and for the 2 nd to 3 rd (2D:3D) and 2 nd to 5 th (2D:5D) digit ratios of the left hand. The digit ratios are lateralized and sexually dimorphic in Greek population. The sexual dimorphism of all digit ratios (except 2D:3D) is stronger in right than left hand.

Background: The ratio of lengths of second to the fourth digit (2D:4D) is a proxy indicator of prenatal sex-hormone exposure. The male has lower 2D:4D than the female. The ratio and its sexual dimorphism vary across ethnicity. The relationships of 2D:4D with anthropometric dimensions are not consistent. Objective: To compare 2D:4D and its sexual dimorphism between the young Indian and Polish populations and to examine the relationship between 2D:4D and anthropometric measures. Methods: This cross-sectional study included 152 Indian (males: 71 females: 81) and 110 Polish (55 each sex) young adults aged between 18 and 25 years. Height, weight, waist and hip circumferences, second and fourth digit lengths were measured. Results: Males had significantly lower 2D:4D than the female in both hands in both the ethnic groups. All the anthropometric measurements were higher in Polish males, including the 2D:4D of both hands, than the Indians, except for BMI and WHR. Polish females had higher digit lengths, height, weight and HC than the Indian females. In Polish males, 2D:4D was negatively associated with height and WHR in both hands. No significant correlation was observed between any anthropometric measure (except for height) and 2D:4D among the Indians. However, the Indian Female had a nearly significant positive correlation between left 2D:4D and HC. In Indian Male correlation between left hand 2D:4D and Height is significant and similar to that of the Polish men. Conclusion: It was not possible to draw any conclusion regarding the nature of association between 2D:4D and anthropometric parameters. The findings indicate a link between fat patterning and digit ratio.

The ratio of the length of the 2nd and 4th digits of the hand is an indicator of prenatal testosterone exposure and has been shown to be a within sex correlate of various abilities, such as visuo-spatial processing in men. However, a number of studies report such links also exist in women, whilst others show no link for either sex. Using a unique paradigm that subdivides visuo-spatial processing into a distinct subset of component skills we found a strong correlation between finger ratio and spatial memory performance specifically under stereo viewing conditions in women. We argue that the current ambiguity regarding links between digit-ratio and visuo-spatial ability is the result of a lack of clarity between the component skills recruited in different visuo-spatial tasks. Our task independently tested a subset of the component skills used in visuo-spatial tasks such as: mental rotation, cross-dimensionality processing and feature detection. Our results show that digit-ratio, a physical parameter linked to prenatal testosterone levels, indicates performance on a distinct aspect of visuo-spatial processing in women, without contradicting previous links for visuo-spatial processing in men. These results offer an explanation for the differences in previous findings linking visuo-spatial processing in both men and women.