On relationships between digit ratio (2D:4D) and two fundamental cognitive drives,empathizing and systemizing,in Japanese sample

Degree of prenatal testosterone exposure in individuals is indexed by the biomarker, digit ratio, which is the length ratio between second and fourth digit fingers (2D:4D). Recent research has suggested a relationship between the digit ratio and individual differences in empathizing and systemizing, which are the two fundamental cognitive drives hypothesized by Baron-Cohen (2003). However, some studies on the relationship between digit ratio and empathy quotient (EQ) and systemizing quotient (SQ) have reported inconsistent results (Manning et al., 2010, von Horn et al., 2010, Voracek and Dressler, 2006). This study examined the relationship between digit ratio and EQ and SQ in a sample of Japanese university students (174 males and 174 females, mean age = 19.6). Results showed that, on average, male digit ratio was lower than female digit ratio, and digit ratio correlated positively with scores on EQ and negatively with scores on SQ, although correlation coefficients were very low. These results suggest that the fetal testosterone level as estimated by the digit ratio is related to individual differences in adult cognitive and behavioral patterns.     

The role of executive function and social‐emotional skills in the development of literacy and numeracy during preschool: a cross‐lagged longitudinal study

The majority of evidence on the interplay between academic and non‐academic skills comes from high‐income countries. The aim of this study was to examine the bidirectional associations between Ghanaian children's executive function, social‐emotional, literacy, and numeracy skills longitudinally. Children (N = 3,862; M age = 5.2 years at time 1) were assessed using direct assessment at three time points over the course of two school years. Controlling for earlier levels of the same skill, early executive function predicted higher subsequent literacy and numeracy skills, and early literacy and numeracy skills predicted higher subsequent executive function, indicating that the development of executive function and academic skills is inter‐related and complementary over time. Early literacy and numeracy predicted subsequent social‐emotional skills, but early social‐emotional skills did not predict subsequent literacy and numeracy skills. The findings provide longitudinal evidence on children's learning and development in West Africa and contribute to a global understanding of the relations between various developmental skills over time.     

Digit ratio and faculty membership: Implications for the relationship between prenatal testosterone and academia

Digit ratio (length of index finger divided by length of ring finger) is an index of exposure to prenatal testosterone. Prenatal testosterone slows the growth rate of the left side of the brain while enhancing growth of the right side. Right hemisphere processing is associated with better visual‐spatial and mathematical abilities, as is digit ratio. Thus, traditional sex differences in visual‐spatial and mathematical abilities can be attributed to differences in exposure to prenatal testosterone, indexed by a sex dimorphic pattern in digit ratio (female=1.00, male=0.98 for UK samples). Additionally, the digit ratio is a marker for within‐sex variance in visual‐spatial ability. This study examines the digit ratio of an academic sample. No sex differences are found and there is a significant difference between the Science Faculty and Social Science Faculty. Social Scientists of both sexes have a ratio consistent with the male norm (0.98) whilst Scientists have a digit ratio consistent with the female norm (1.00). These results are discussed in terms of the lower normal range of male testosterone being associated with highest visual spatial abilities. Relationships with fertility and Dyslexia are also identified.     

Digit ratio (2D:4D), academic performance in computer science and computer-related anxiety

Being able to use information communication technology (ICT) effectively has become an essential element of participation within an increasingly digital culture. However, there are differences in participation within this digital culture. Prenatal testosterone exposure is thought to influence the development of numeric capabilities and relate to levels of anxiety, both of which contribute towards engagement with ICT. This study examined whether an index of prenatal exposure to testosterone, digit ratio (2D:4D), is related to successful involvement within a computer-technology context - performance in a Java programming course. Three studies (N = 73,75,65) identified a consistent negative correlation between 2D:4D digit ratio and attainment (r ≈ −0.2). A fourth study (N = 119) found that 2D:4D digit ratio positively correlated with two indices of computer-related anxieties, as well as anxiety sensitivity (r = 0.32/0.51). These results suggest that males and females who have been exposed to higher levels of testosterone within the womb perform better upon academic assessments of Java-related programming ability within computer science education, and have lower levels of computer-related anxieties outside computer science education. Thus, the 2D:4D index of prenatal testosterone exposure correlated with the two factors that directly impact upon ICT engagement, which is increasingly essential to effectively participate within educational and occupational environments.     

Alcohol and nicotine intake and prenatal level of androgens measured by digit ratio

The purpose of this study was to examine the associations between using unhealthy substances and the digit ratio (2nd to 4th digit length ratio, 2D:4D) which is supposed to indicate the prenatal testosterone level. The subjects were 455 students, 225 women and 230 men. Participants declared their frequency of smoking and alcohol drinking. There was no significant difference in digit ratios between subjects regularly using both nicotine and alcohol and those who took none of them. When analyzing the two substances separately, there was no relationship between 2D:4D and alcohol drinking, whereas left hand 2D:4D was positively related to smoking only for women (nonsignificant trend was observed for right hand). Contrary to the previous study, our results indicate that there is no relationship between 2D:4D and alcohol drinking. There is, however, a subtle influence of prenatal testosterone levels for cigarette smoking habits in the case of women.     

Early experience of sex hormones as a predictor of reading, phonology, and auditory perception

Previous research has indicated possible reciprocal connections between phonology and reading, and also connections between aspects of auditory perception and reading. The present study investigates these associations further by examining the potential influence of prenatal androgens using measures of digit ratio (the ratio of the lengths of the index and ring fingers). Those with low digit ratios (shorter index finger and therefore in the masculine direction) are hypothesised to have experienced greater "masculinisation" in the uterus. ANCOVA analyses using a verbal reasoning task as a covariate showed that only phonology was influenced by digit ratio in the right hand indicating that hypothesised androgen effects were inhibiting phonology; however this effect in the left hand was reduced and instead there was an effect indicating an inhibition of androgens on reading. Furthermore, subjects with low right-hand digit ratios were also impaired compared to those with high right-hand digit ratios in an auditory saltation task. These findings are discussed in terms of the possible effects of androgens on early brain development impairing aspects of the temporal processing of sounds by the left hemisphere, which could also have a secondary influence on developing phonology and literacy skills.     

Sporting Achievement: What Is the Contribution of Digit Ratio?

Second-to-fourth digit ratio, a marker for prenatal testosterone levels, has been shown to be associated with sporting achievement in men. It is unclear, however, whether digit ratio makes a contribution over and above salient personality variables. The present study, which included female participants, measured four personality traits and one cognitive ability (mental rotation) that have been linked to both sports achievement and sex. The significant relationship between digit ratio and sporting achievement was nearly identical in women and men. A multiple regression showed that when significant correlates of sporting ability (weight, height, years playing, hours per week training, social potency, and mental rotation) were entered first, the contribution of digit ratio remained highly significant. We suggest that physiological as well as psychological factors may be an important avenue for future study.     

Testosterone and domain-specific risk: Digit ratios (2D:4D and rel2) as predictors of recreational, financial, and social risk-taking behaviors

Prenatal testosterone has important effects on brain organization and future behavior. The second-to-fourth digit length ratio (2D:4D), a proxy of prenatal testosterone exposure, has been linked to a wide variety of sexually differentiated dispositions and behaviors. We examine the relationship between digit length ratios (2D:4D and rel2, the length of the second finger relative to the sum of the lengths of all four fingers) and risk-taking behaviors across five domains: financial, social, recreational, ethical, and health. In a sub-sample of male Caucasians (ethnically homogeneous), lower rel2 was predictive of greater financial, social, and recreational risk-taking, whereas lower 2D:4D was predictive of greater risk-taking in two domains (social and recreational). In the full male sub-sample (ethnically heterogeneous), the only significant correlation was a negative association between 2D:4D and financial risk. A composite measure of risk-taking across all five domains revealed that both rel2 and 2D:4D were negatively correlated with overall risk-taking in both male sub-samples. No significant correlations were found in the female sub-samples. Finally, men were more risk-seeking than women across all five contexts.     

Scholastic Assessment or g? The relationship between the Scholastic Assessment Test and general cognitive ability

There is little evidence showing the relationship between the Scholastic Assessment Test (SAT) and g (general intelligence). This research established the relationship between SAT and g, as well as the appropriateness of the SAT as a measure of g, and examined the SAT as a premorbid measure of intelligence. In Study 1, we used the National Longitudinal Survey of Youth 1979. Measures of g were extracted from the Armed Services Vocational Aptitude Battery and correlated with SAT scores of 917 participants. The resulting correlation was.82 (.86 corrected for nonlinearity). Study 2 investigated the correlation between revised and recentered SAT scores and scores on the Raven's Advanced Progressive Matrices among 104 undergraduates. The resulting correlation was.483 (.72 corrected for restricted range). These studies indicate that the SAT is mainly a test of g. We provide equations for converting SAT scores to estimated IQs; such conversion could be useful for estimating premorbid IQ or conducting individual difference research with college students.     

Individual differences in 2D:4D digit-ratios and otoacoustic emissions: Do they share a common developmental origin?

Differences across individuals in both 2D:4D, the ratio of the lengths of the 2nd-4th digit, and in otoacoustic emissions (OAEs), have been hypothesized to arise from differences in androgen exposure prenatally. Contrary to this hypothesis, however, McFadden and Shubel (2003) found no significant correlation between digit-ratios and OAE production. To further investigate the hypothesis of a common developmental origin, the current study assessed correlations between individual differences in 2D:4D and OAEs in 131 normally-hearing adults. All possible ratios of the 2nd, 3rd, 4th, and 5th digits were computed and OAEs, both spontaneously produced and in response to audible clicks, were measured. Observed correlations between digit length ratios and OAEs were largely nonsignificant. No significant correlations were found between 2D:4D and any of the five OAE measures. Fundamental differences in developmental timing and duration, postnatal influences, or factors other than prenatal androgens may explain the lack of associations.     

Masculinised brain and romantic jealousy: Examining the association between digit ratio (2D:4D) and between- and within-sex differences

We examined the relationship between second-to-fourth digit ratio (2D:4D), a correlate of prenatal testosterone exposure, and distress at sexual versus emotional infidelity in hypothetical scenarios of relationship threat. As predicted, a significant negative association was found between 2D:4D and greater distress at sexual infidelity for the whole sample (N = 179, females = 101). While this novel finding supports the view of romantic jealousy as a sexually-dimorphic adaptation, we explore reasons for the relatively weak association and discuss how underlying differences in brain structure could have influenced sex-specific behavioural capacities in romantic jealousy. We suggest a useful direction for future research will be to develop novel methods that facilitate the investigation of implicit emotional, rather than explicit cognitive, processes in response to pair-bond threat.     

Early literacy and early numeracy: the value of including early literacy skills in the prediction of numeracy development

The purpose of this study was to examine whether early literacy skills uniquely predict early numeracy skills development. During the first year of the study, 69 3- to 5-year-old preschoolers were assessed on the Preschool Early Numeracy Skills (PENS) test and the Test of Preschool Early Literacy Skills (TOPEL). Participants were assessed again a year later on the PENS test and on the Applied Problems and Calculation subtests of the Woodcock–Johnson III Tests of Achievement. Three mixed effect regressions were conducted using Time 2 PENS, Applied Problems, and Calculation as the dependent variables. Print Knowledge and Vocabulary accounted for unique variance in the prediction of Time 2 numeracy scores. Phonological Awareness did not uniquely predict any of the mathematics domains. The findings of this study identify an important link between early literacy and early numeracy development.     

High cognitive sensitivity to activational effects of testosterone in parents of offspring with autism spectrum disorders

The existence of mild forms of autistic-like characteristics in parents of children with autism spectrum disorders (ASDs) has been defined as a broader autistic phenotype (BAP). Excessive prenatal exposure to testosterone (T) seems to play a role in its development. The aims of this study were to characterize whether ASD parents show masculinized brains or high T prenatal exposure compared to a normative population, using cognitive questionnaires, and also to examine the T level changes in response to different cognitive tasks. ASD parents were found to present higher autistic and lower empathic trait scores than controls. They also have higher T levels and magnitude of T response to cognitive tasks. Specific correlation patterns between masculinized brain types and T levels were observed only in ASD parents. Thus, it seems that first-degree relatives of people with ASD have high T levels during task performance, which, in turn, produce slight cognitive masculinization. Our findings should be considered for understanding the role of androgens in the etiology of ASD. Nevertheless, the masculinization parameters described throughout the study are subtle and require further analysis.     

2D:4D in men is related to aggressive dominance but not to sociable dominance

It has been shown that a smaller ratio between the length of the second and fourth digit (2D:4D) is an indicator of the exposure to prenatal testosterone (T). This study measured the 2D:4D of men and assessed dominance as a personality trait to investigate indirectly if the exposure to prenatal T is related to a dominant personality later in life. Results showed that men had a more aggressive dominant personality when having a more masculine (lower) 2D:4D, while there was no relationship between sociable dominance and 2D:4D. Findings from this study indicate that it is important to distinguish different forms of dominance since other studies failed to find relationships between dominance and 2D:4D.     

Are occupational interests hormonally influenced? The 2D:4D-interest nexus

Occupational interests constitute a psychological variable with pronounced sex differences. Whereas males are more interested in things, females primarily take an interest in people. As various studies with mammals and humans documented the role of androgen exposure on sex-typical behavior, we assumed that androgen levels are associated with occupational interests. In our study, we used 2D:4D digit ratio as an indicator of prenatal androgen levels and finger lengths as an indicator of post-pubertal androgen levels. Occupational interests were measured with a standard interest inventory. We hypothesized that finger lengths and ratios indicating high androgen levels are associated with stronger interests in things and weaker interests in people. All measures were gathered using an online interest inventory thereby leading to sufficient statistical power (N = 8646). Results partly confirmed our hypotheses. We found significant correlations between finger lengths and interests in things for males. Moreover, in the case of males we identified significant correlations between finger lengths (positive) as well as digit ratios (negative) with realistic interests and significant correlations between finger lengths (negative) and social interests, which are a marker variable of the people-things dimension.     

Relationships between digit ratio (2D:4D) and sex-typed play behavior in pre-school children

Juvenile play shows sex differences in animals and humans. Animal studies and a recent study in humans suggest that testosterone exposure during early development plays a key role. Here we report on the relationship between children’s sex-typed play behavior and digit ratio (2D:4D), a putative negative correlate of prenatal testosterone. 2D:4D and sex-typed play behavior as assessed by parents were negatively correlated in a sample of 83 pre-school boys but not in a sample of 93 girls. This finding lends some support to the ideas that early testosterone has a masculinising effect upon sex-typed play behavior in humans and that 2D:4D is a valuable tool for studying effects of early testosterone on human behavior.     

Digit ratios,but not facial width-to-height ratios,are associated with the priority placed on attending to faces versus bodies

Testosterone has been linked to a sexual preference for bodies rather than faces. Low digit ratio (2D:4D) and high facial width-to-height ratio (WHR) are associated with high prenatal testosterone. We tested whether low 2D:4D and high facial WHR were correlated with a preference for bodies over faces. Our sample consisted of 109 college students (64 males). A two-way analysis of variance demonstrated a significant main effect of digit ratio on the priority placed on paying attention to faces or bodies such that low 2D:4D was linked to a preference for bodies, but the effect of sex was not significant. There were no significant interaction effects. Another two-way analysis of variance revealed no significant effects for facial WHR and attentional priority but significant associations between sex and attentional priority. There were no significant interaction effects. Our findings indicate that individuals with low digit ratios tended to pay more attention to bodies than to faces compared with individuals with higher digit ratios, independently of sex. We also found that males tended to pay more attention to bodies than to faces compared with females, independently of facial WHR.     

Lack of correlation between digit ratio (2D:4D) and Baron-Cohen’s “Reading the Mind in the Eyes” test, empathy, systemising, and autism-spectrum quotients in a general population sample

The second-to-fourth digit ratio (2D:4D) is sexually differentiated and is a likely biomarker for the organisational (permanent) effects of prenatal testosterone on the human brain. Recent research has highlighted a possible role of prenatal testosterone levels in both the etiology of autism-spectrum disorders and in sex and individual differences in cognitive styles of the normal mind (Baron-Cohen’s Extreme Male Brain Theory of Autism and Empathising/Systemising Theory). Importantly, autistic children present lower (hypermasculinised) 2D:4D than healthy controls. Based on these accounts, we investigated the relation of 2D:4D with Baron-Cohen’s measures of empathising (“Reading the Mind in the Eyes” test, RMET; Empathy Quotient, EQ), systemising (Systemising Quotient, SQ), and autistic-like traits (Autism-Spectrum Quotient, AQ) in the general population (N = 423 Austrian adults). Whereas sex differences into the expected direction and of expected size were obtained for all variables and internal scale consistencies tallied to retrievable reference values, 2D:4D was unrelated to RMET, EQ, SQ, and AQ scores. Candidate explanations for this lack of correlation might be possible developmental timing differences in the expression of 2D:4D and empathising/systemising, qualitative (as opposed to quantitative) functional differences between the normal and the autistic mind, or the suboptimal psychometric properties of the measures.     

The 2nd to 4th digit ratio (2D:4D) and eating disorder diagnosis in women

Eating disorders are more common in females than in males and are believed to be caused, in part, by biological and hormonal factors. Digit ratio or 2D:4D (the ratio of the 2nd to the 4th digit) is considered to be a proxy for prenatal testosterone (PT) and prenatal oestrogen (PE) exposure. However, how 2D:4D may be related to type of eating pathology is unknown. The relationship between 2D:4D and eating disorder diagnosis was investigated in recovered and currently eating disordered (n = 31) and control (n = 99) women. Mean 2D:4D ratio was significantly lower (indicating higher levels of PT and lower levels of PE) in anorexic (AN) compared to bulimic (BN) women, with controls intermediary. In eating disordered women, 2D:4D was positively and significantly related to current weight, lowest weight and current BMI, with strongest associations for right 2D:4D. Among women, low 2D:4D is related to AN and high 2D:4D to BN, suggesting a differential causal influence of prenatal sex hormones on later eating pathology.     

Second to fourth digit ratio and numerical competence in children

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.