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Abstract: Three new studies (N= 132, 623, 1112) did not yield hypothesized associations between digit ratio (2D:4D), an assumed negative correlate of prenatal testosterone, and psychometrically measured sex-role orientation (positive association with femininity, negative ones with masculinity and masculinity-femininity difference scores) among heterosexuals of either sex. Meta-analysis of the pertinent literature (N= 6311, 28 studies from 10 countries, 46% unpublished) showed only men’s (but not women’s) left-hand (but not right-hand) 2D:4D reliably related as expected (positively) to femininity. This effect was tiny (0.14% attributable variance) and possibly non-robust (crucially dependent on one large study included). Hence, the cumulative evidence does not support systematic, robust, noteworthy within-sex correlations between 2D:4D and the masculinity/femininity personality dimensions. [Copyright &y& Elsevier]

Abstract: The sexually differentiated second-to-fourth digit ratio (2D:4D) is currently frequently utilized in individual differences research as a putative indicator of the masculinizing brain organization effects of prenatal testosterone. This preamble introduces the journal special issue on this theme, entitled “Digit ratio (2D:4D) and individual differences research”. Notes regarding the background, history, and recent progress of 2D:4D research are provided, and the background of the special issue and the contents of its 11 research articles are briefly summarized. [Copyright &y& Elsevier]

Abstract: Two studies examined beliefs about the personality of male butchers and hunters and the factuality of such beliefs. These professions’ daily routines involve killing animals and handling their carcasses, acts that could be facilitated by specific personality constellations. Study 1 (102 raters) evidenced perceptions of higher aggressiveness and masculinity of butchers/hunters and higher self-esteem (hunters only), as compared with average men. In contrast, Study 2 found little evidence for the factuality of such beliefs, based on multi-method personality assessments in a case-control design of 96 men (23 and 25 dyads including one butcher or hunter, matched with same-generation, other-occupation friends or relatives). Only implicit, but not explicit, aggressiveness (measured with an Implicit Association Test) was higher in butchers/hunters than in controls. Both masculinity (whether measured unobtrusively [digit ratio, 2D:4D] or explicitly) and self-esteem (whether measured implicitly [name-letter effect] or explicitly) were comparable for butchers/hunters and controls. Lower self-reported conscientiousness, extraversion, and openness in butchers/hunters than controls were not generalizable to informant reports of these Big Five dimensions. Discussion focuses on the merits of utilizing belief-factuality contrasts, controlled designs, and multi-method assessments in personality research. [ABSTRACT FROM AUTHOR]

Abstract: Previously reported associations between low (male-typical) digit ratio (2D:4D), a putative pointer to prenatal testosterone exposure, and high (male-typical) sensation seeking have been inconsistent across studies (alternately present for men, women, either sex, or neither). Addressing this question again in three new studies (N =198, 188, 1118) produced similarly erratic findings. Meta-analysis of the entire literature (13 studies with nearly 3000 individuals, including unpublished accounts) showed that the current cumulative evidence does not support any negative correlations between 2D:4D and sensation seeking traits. The only significant meta-analytical finding was for right-hand 2D:4D and the experience seeking facet of sensation seeking in both sexes, but this effect accounted for merely 0.4% attributable variance, and moreover was directionally opposite to expectation (i.e., a positive correlation). Discussed are inherent limitations of narrow-scoped approaches (such as via 2D:4D) for elucidating the biological bases of individual difference variables with evidentially intricate neurochemical underpinnings (such as sensation seeking). [Copyright &y& Elsevier]

Abstract: Associations of paranormal and superstitious beliefs with digit ratio (2D:4D) and absolute finger length (putatively indexing prenatal and pubertal-adolescent androgen levels, respectively), fluctuating asymmetry (FA; indexing developmental instability), and body measures at birth (indexing non-optimal fetal growth) were examined in a sample of 1118 adults. Higher (feminised) 2D:4D correlated with stronger beliefs in men, even when controlled for age, education, adult height and weight, and birth length and weight. Shorter (feminised) finger length correlated with more superstition among women, but not when controlled for the same covariates. Finger FA was unrelated to beliefs in both sexes. Shorter birth length (in men and women) and lighter adult weight (in women) were associated with stronger beliefs. Effects of 2D:4D on men’s beliefs were weak (1–3% attributable variance), but commensurable with those of known non-biological belief correlates (age: 1%; education: 2%). This evidence may be informative for narrowing down possible developmental pathways of paranormal and superstitious beliefs. Propensities contributing to sex and individual differences in these beliefs probably arise in utero, may partly be due to prenatal testosterone and other prenatal programming effects, but less likely due to pubertal-adolescent androgen action or developmental instability. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Background: Right-hand preference is related to stronger right-directional asymmetry in the length of proximal upper-limb bones, although the relationships of hand preference with directional asymmetry in phalangeal bone lengths are not known. Furthermore, dorsal digit length is an easy-to-measure, faithful proxy of X-rayed phalangeal bone length (which is costly and difficult to measure).Aim: To study the effects of hand preference, sex, and age on right-left (R-L) asymmetry in dorsal digit lengths.Methods: We measured all dorsal digit lengths (except the thumb) in comparable numbers of left-handers and right-handers in samples of adults (N = 151, age: M = 22.6 years, SD = 3.3) and children (N = 65, age: M = 5.0 years, SD = 1.0).Results: Right-handers and adults had stronger right-directional asymmetry in digit lengths than left-handers and children. A Bayesian analysis yielded an 'extremely strong likelihood' of no sex differences in the R-L asymmetry of dorsal digit lengths 2 and 4.Conclusions: The effects of hand preference, sex, and age on R-L asymmetry appear to be similar for phalangeal bone length and other (proximal) upper-limb bone lengths. Two distinct biologic mechanisms (i.e., a general right-directional asymmetry mechanism and a handedness-related directional asymmetry mechanism) may contribute to observed R-L asymmetry in limbs. Fingertip fat and bone digit length do not seem to contribute to sex differences in the R-L asymmetry (Dr-l) of the widely studied second-to-fourth digit ratio (2D:4D). [ABSTRACT FROM AUTHOR]