The second-to-fourth digit ratio (2D:4D) is a sexually dimorphic somatic trait and has been proposed as a biomarker for the organizational, i.e., permanent, effects of prenatal testosterone on the human brain. Accordingly, recent research has related 2D:4D to a variety of sex-dependent, hormonally influenced traits and phenotypes. The geographical variation in typical 2D:4D is marked and presen...

Testosterone, particularly prenatal testosterone, has been implicated in the aetiology of many extragenital sexually dimorphic traits. It is difficult to test directly for the effect of prenatal testosterone in humans. However, Manning, Scutt, Wilson, and Lewis-Jones (1998b) have recently shown that the ratio of the length of the 2nd and 4th digits (2D:4D) in right hands negatively predicts tes...

Finger-length ratio (second to fourth finger; 2D:4D) has been associated with various measures thought to be related to prenatal androgens. In addition, hormone-transfer theory posits that hormones can transfer between twins. We examined 2D:4D in same-sex (SS) and opposite-sex (OS) dizygotic twins to test both propositions. Results show that 2D:4D is masculinized in OS females compared to SS fe...

The ratio between second and fourth finger (2D:4D) is sexually dimorphic; it is lower in men than in women. Studies using broad personality domains yielded correlations of 2D:4D with neuroticism, extraversion or agreeableness, but the obtained results have been inconsistent. We correlated 2D:4D of 184 women and 101 men with their scores in Cattell’s 16 Personality Factor (16PF) Questionnaire. W...

The ratio of the second-to-fourth finger lengths (2D:4D) has been proposed as an indicator of prenatal sex differentiation. However, 2D:4D has not been studied in the closest living human relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). We report the results from 79 chimpanzees and 39 bonobos of both sexes, including infants, juveniles, and adults. We observed the expected s...

The potential dependence of second-to-fourth digit ratio (2D:4D) on latitude has been discussed in recent papers in this journal (Hurd & van Anders, 2007; Loehlin, McFadden, Medland, & Martin, 2006, 2007). Such an association was first suggested by Manning (2002), who proposed that 2D:4D was highest at intermediate latitudes and lowest at the equator and at high latitudes. In their Fig. 1, Hurd...

INTRODUCTION The ratio of the length of the second finger to the fourth finger (2D:4D) in humans is considered as a putative marker of prenatal exposure to testosterone, and has been progressively adopted as one useful tool to evaluate the effect of prenatal hormones in some traits such as physical ability. Handgrip strength is one authentic measure of physical ability and is generally used on ...

BACKGROUND The prevalence of autism spectrum disorders (ASDs) is higher in men than in women. The extreme male brain theory proposes that excessive prenatal testosterone activity could be a risk factor for ASDs. However, it is unclear whether prenatal sex hormone activity is a risk factor for women. The ratio of the length of the second to fourth digits (2D:4D) is considered to be a biomarker o...

It has been suggested that autism may arise as the result of exposure to high concentrations of prenatal testosterone. There is evidence that the ratio of the lengths of the 2nd and 4th digit (2D:4D) may be negatively correlated with prenatal testosterone. We measured 2D:4D in 95 families recruited via the National Autistic Society, UK. The sample comprised a total 72 children with autism (62 m...

Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. This ratio is considered to be a biomarker of the balance between fetal testosterone (T) and estrogen (E) in a narrow window of early ontogeny. Evidence for this assertion is derived from direct and indirect measures of prenatal hormonal exposure (in experimental animals, via amniotic fluid samples and in the study...