Are 2D:4D finger-length ratios related to sexual orientation? Yes for men, no for women.

Abstract

The ratio of index and ring finger lengths (2D:4D) is thought to be a marker of prenatal androgen exposure. In a sample of over 2,000 participants, men had significantly lower 2D:4D ratios than women (d ϭ .36 and .23 for right and left hands, respectively), and these results were consistent across ethnic groups. Heterosexual men had significantly lower (more male typical) 2D:4D ratios than gay men (d ϭ .32 and .31 for right and left hands, respectively), and these results tended to be consistent across ethnic groups. Heterosexual and lesbian women showed no significant differences in 2D:4D ratios, after ethnicity was taken into account. The current findings add to evidence that prenatal hormonal factors may be linked to men's sexual orientation.

Second to fourth digit ratio and cooperative behavior

“…In accordance with previous literature (e.g. Fink et aI., 2004;Lippa, 2003;Manning, 2002;Williams et aI., 2003), 2D:4D was significantly lower for men (M = .956, SD = .025) than for women (M = .975, SD = .027; t(68) = -3.01,p <.005).…”

The 2nd–4th digit ratio (2D:4D) and neck circumference: implications for risk factors in coronary heart disease

“…It should be noted that accurate calculation of 2D:4D is not dependent on measurement of finger lengths to 0.01 mm as sexual dimorphism in 2D:4D has been shown from measurements made to the nearest mm with a ruler or tape measure. 22 Each finger was measured twice and comparisons between first and second 2D:4D ratios measurements gave an intraclass correlation coefficient of r 1 ¼ 0.89 for the right hand and r 1 ¼ 0.79 for the left. We used repeated measures ANOVA to calculate the ratio (F) between measurement error (the differences between successive measures of 2D:4D) and between-participant differences.…”

Digit ratios (2D:4D) determined by computer‐assisted analysis are more reliable than those using physical measurements, photocopies, and printed scans

“…Unfortunately, these associations with 2D:4D have been dampened by the enormous amount of nonreplication that has been reported among studies investigating similar study populations (e.g. Male and female homosexuality- Lippa, 2003;Robinson and Manning, 2000;Williams et al, 2000; Polycystic ovary syndrome-Bloski et al., 2008;Cattrall et al, 2005; Aggression-Bailey and Hurd, 2005;Hampson et al, 2008).Studies designed to test the notion that prenatal androgens program certain traits and phenotypes require a standardized, validated method of measuring fingers and determining 2D:4D . This is particularly important as effect sizes on 2D:4D are generally only moderate to low (Kemper and Schwerdtfeger, in press).…”

“…Previous studies in humans have shown low digit ratios (2D:4D) to be associated with a variety of traits including, enhanced visual spatial ability (Burton et al, 2005;van Anders and Hampson, 2005), increased athleticism (Honekopp et al, 2006a), female homosexuality (Brown et al, 2002;Hall and Love, 2003;Kraemer et al, 2006;Williams et al, 2000), decreased susceptibility to coronary artery disease (Fink et al, 2003;Manning and Bundred, 2000), and greater fertility potential in men (Manning et al, 1998) but lower fertility potential in women (Cattrall et al, 2005). By contrast, high 2D:4D were shown to be associated with high verbal fluency (Burton et al, 2005), increased emotional behavior (Williams et al, 2003), lower waist-hip ratios (Fink et al, 2003), male homosexuality (Lippa, 2003) and an increased risk of breast cancer (Manning and Bundred, 2000). Unfortunately, these associations with 2D:4D have been dampened by the enormous amount of nonreplication that has been reported among studies investigating similar study populations (e.g.…”

“…Unfortunately, these associations with 2D:4D have been dampened by the enormous amount of nonreplication that has been reported among studies investigating similar study populations (e.g. Male and female homosexuality -Lippa, 2003;Robinson and Manning, 2000;Williams et al, 2000; Polycystic ovary syndrome- Bloski et al, 2008;Cattrall et al, 2005;Aggression-Bailey and Hurd, 2005;Hampson et al, 2008).…”