Second to fourth digit ratio (2D:4D) of the right hand is associated with nociception and augmenting-reducing

Penile length-somatometric parameters relationship in healthy Egyptian men

This study aimed to assess the penile length-somatometric parameters relationship in healthy Egyptian men. Two thousand physically normal men (22-40 years) were subjected to measurement of stretched penile length, glans penis, testis size, index finger, weight, height, span, body mass index (BMI), waist circumference, hip circumference and waist/hip ratio. The mean stretched penile length of the studied subjects was 13.84 ± 1.35 cm (range 12-19 cm), and the mean glans penis length was 2.6 ± 0.4 cm (range 1.7-3.8 cm). Penile length demonstrated positive significant correlation with glans penis length, index finger length, BMI and significant negative correlation with waist/hip ratio. On the other hand, penile length demonstrated nonsignificant correlation with age, weight, height, waist circumference, span or testicular size. It is concluded that the penile length-somatometric parameters relationship in healthy Egyptian men is mostly related to glans penis and index finger lengths.

Second to fourth digit ratio: a predictor of adult penile length

The second to fourth digit ratio (2D:4D) has been proposed as a putative biomarker for prenatal testosterone and covaries with the sensitivity of the androgen receptor (AR). Both prenatal testosterone and the AR play a central role in penile growth. In this study, we investigated the relationship between digit ratio and penile length. Korean men who were hospitalized for urological surgery at a single tertiary academic centre were examined in this study, and 144 men aged 20 years or older who gave informed consent were prospectively enrolled. Right-hand second- and fourth-digit lengths were measured by a single investigator prior to measurement of penile length. Under anaesthesia, flaccid and stretched penile lengths were measured by another investigator who did not measure nor have any the information regarding the digit lengths. Univariate and multivariate analysis using linear regression models showed that only height was a significant predictive factor for flaccid penile length (univariate analysis: r=0.185, P=0.026; multivariate analysis: r=0.172, P=0.038) and that only digit ratio was a significant predictive factor for stretched penile length (univariate analysis:r=-0.216, P=0.009; multivariate analysis: r=-0.201, P=0.024; stretched penile length=-9.201×digit ratio + 20.577). Based on this evidence, we suggest that the digit ratio can predict adult penile size and that the effects of prenatal testosterone may in part explain the differences in adult penile length.

Lack of association between digit ratio (2D:4D) and assertiveness: replication in a large sample

Findings regarding within-sex associations of digit ratio (2D:4D), a putative pointer to long-lasting effects of prenatal androgen action, and sexually differentiated personality traits have generally been inconsistent or unreplicable, suggesting that effects in this domain, if any, are likely small. In contrast to evidence from Wilson's important 1983 study, a forerunner of modern 2D:4D research, two recent studies in 2005 and 2008 by Freeman, et al. and Hampson, et al. showed assertiveness, a presumably male-typed personality trait, was not associated with 2D:4D; however, these studies were clearly statistically underpowered. Hence this study examined this question anew, based on a large sample of 491 men and 627 women. Assertiveness was only modestly sexually differentiated, favoring men, and a positive correlate of age and education and a negative correlate of weight and Body Mass Index among women, but not men. Replicating the two prior studies, 2D:4D was throughout unrelated to assertiveness scores. This null finding was preserved with controls for correlates of assertiveness, also in nonparametric analysis and with tests for curvilinear relations. Discussed are implications of this specific null finding, now replicated in a large sample, for studies of 2D:4D and personality in general and novel research approaches to proceed in this field.

Is the Index Finger and Ring Finger Ratio (2D:4D) Reliable Predictor of Semen Quality?

PURPOSE

The purpose of this paper is to test the validity of hypothesis that the index finger and ring finger ratio (2D:4D) is related with men's semen quality.

MATERIALS AND METHODS

We set two groups of healthy young male student (mean age 23.9) who have different 2D:4D ratio from different departments of Chosun University. One group consists of 26 men whose 2D:4D ratio is higher than 1 (mean 1.06), and the other group consists of 33 men whose 2D:4D ratio is lower than 1 (mean 0.94). Their semen was collected by masturbation and examined.

RESULTS

A comparative analysis revealed that there is no relation between semen quality and the 2D:4D ratio. The group of 2D:4D>/=1 showed a semen volume of 3.66+/-1.64 ml, on the other hand, the group of 2D:4D<1 showed a semen volume of 3.73+/-1.40 ml. No statistical correlation was found (p=0.82). The view of sperm count and motile sperm in single ejaculated semen also showed no statistically significance with 2D:4D ratio (p=0.84, p=0.43, respectively).

CONCLUSIONS

The 2D:4D ratio has no statistically significant correlation with the semen quality of health young male. Thus, measurements of finger length cannot be a reliable indicator of semen quality and testicular function.

Digit ratio (2D:4D) is associated with traffic violations for male frequent car drivers

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.

Scientometric analysis and bibliography of digit ratio (2D:4D) research, 1998-2008

A scientometric analysis of modern research on the second-to-fourth digit ratio (2D:4D), a widely studied putative marker for prenatal androgen action, is presented. In early 2009, this literature totalled more than 300 publications and, since its initiation in 1998, has grown at a rate slightly faster than linear. Key findings included evidence of publication bias and citation bias, incomplete coverage and outdatedness of existing reviews, and a dearth of meta-analyses in this field. 2D:4D research clusters noticeably in terms of researchers, institutions, countries, and journals involved. Although 2D:4D is an anthropometric trait, most of the research has been conducted at psychology departments, not anthropology departments. However, 2D:4D research has not been predominantly published in core and specialized journals of psychology, but rather in more broadly scoped journals of the behavioral sciences, biomedical social sciences, and neurosciences. Total citation numbers of 2D:4D papers for the most part were not larger than their citation counts within 2D:4D research, indicating that until now, only a few 2D:4D studies have attained broader interest outside this specific field. Comparative citation analyses show that 2D:4D research presently is commensurate in size and importance to evolutionary psychological jealousy research, but has grown faster than the latter field. In contrast, it is much smaller and has spread more slowly than research about the Implicit Association Test Fifteen conjectures about anticipated trends in 2D:4D research are outlined, appendixed by a first-time bibliography of the entirety of the published 2D:4D literature.

The Relation of Digit Ratio (2D:4D) and Absolute Finger Length to Pavlovian Temperament Dimensions

The associations of digit ratio (2D:4D), a likely marker for prenatal androgen exposure, and absolute finger length, a likely marker for postnatal androgen exposure, with self-reports on three Pavlovian temperament dimensions (strength of excitation, strength of inhibition, and mobility of nervous processes) were investigated in a sample of 84 men and 114 women. In men, left-hand 2D:4D was weakly, but significantly, negatively associated with strength of inhibition, and also weakly negatively, but not significantly, associated with the two other temperament dimensions. These effects were absent for men's right-hand 2D:4D. Finger lengths of both hands in men were weakly, but significantly, positively associated with mobility of nervous processes scores. All associations for women were negligible. Both prenatal and postnatal androgen action may contribute to small amounts of individual differences in Pavlovian temperament dimensions in men but apparently not in women.