Only four studies provide a direct test of the link between prenatal androgen and digit ratio two of the four studies found confirming evidence, and there are caveats about those findings. an observed sex difference in children, and associations with characteristics also putatively associated with prenatal androgen ( 13). There is little evidence to show that digit ratio is in fact an indicator of prenatal androgen exposure. There are few systematic attempts to explore the inconsistent findings, with notable exceptions of a metaanalysis of associations between digit ratio and spatial ability ( 11) and a reanalysis of data on associations between digit ratio and sexual orientation ( 12). 1 and 10): although there are some expected associations between digit ratio and a variety of characteristics, there are also failures to find associations (even with large samples) and associations that are in the opposite direction to expectation.

The findings are inconsistent (discussed, for example, in Refs. be more aggressive, have higher spatial ability) than individuals with a higher digit ratio. Given the assumptions about digit ratio and the direction of the sex difference, the expectation is that, within sex, individuals with a lower digit ratio will be more male typed ( e.g. The link between digit ratio and the characteristic is considered to be mediated by between-person variations in anatomical structures subserving that characteristic in the case of psychological characteristics, the anatomical structure is the brain. An association between digit ratio and some characteristic is thus considered to result from between-person variations in prenatal androgen leading to between-person variations in that characteristic. Digit ratios are assumed to mark individual differences in prenatal androgen exposure. body shape, fertility, cardiovascular risk). sexual orientation, spatial ability, risk taking, aggression, gendered interests, autism), and physical ( e.g. Digit ratio has been assumed to reflect testosterone exposure during the second trimester of gestation because of the sex difference detectable in childhood and because of postulated mechanisms regarding digit development ( 4, 9).Ĭlaims about androgen effects on digit ratio have led to its widespread use, and there is now an extensive literature examining links between digit ratio and sex-typed characteristics, both psychological ( e.g. Although most studies of digit ratio trace back to the work of Manning and colleagues ( 4, 5, 6), there is earlier work on this and related characteristics ( e.g. Men have a longer fourth digit relative to the second digit than do women. The ratio is lower in boys and men than girls and women. This has led to a search for biomarkers, physical characteristics that are shaped by prenatal androgen exposure and that can be measured postnatally to reflect that exposure.Ī biomarker that has generated considerable interest is digit ratio, the ratio of the second (index) finger to the fourth (ring) finger, 2D:4D ( 4, 5).

Nevertheless, the methods currently available to study links between prenatal hormones and postnatal behavior are difficult and expensive to use, and studies require many years to complete. childhood-gendered interests have been related to testosterone levels in amniotic fluid ( 3). Such findings are increasingly being verified in typical individuals, i.e. child and adolescent activity interests, aggression, interest in babies, sexual orientation) are associated with the amount of prenatal androgen exposure ( 1), confirming studies in nonhuman species ( 2). Evidence from people with disorders of sex development, resulting in a discordance between prenatal hormone exposure and rearing sex, shows that several sex-related characteristics ( e.g. Sex-related psychological characteristics are increasingly being investigated from a neuroscience perspective, with particular interest in the permanent neural and behavioral effects of sex hormones present during prenatal development.

Finger 2d 4d ratio