Original Research Article
Digit ratio (2D:4D), dominance, reproductive success, asymmetry, and sociosexuality in the BBC Internet Study
Article first published online: 23 APR 2008
Copyright © 2008 Wiley-Liss, Inc.
American Journal of Human Biology
Volume 20, Issue 4, pages 451–461, July/August 2008
How to Cite
Manning, J. T. and Fink, B. (2008), Digit ratio (2D:4D), dominance, reproductive success, asymmetry, and sociosexuality in the BBC Internet Study. Am. J. Hum. Biol., 20: 451–461. doi: 10.1002/ajhb.20767
- Issue published online: 12 JUN 2008
- Article first published online: 23 APR 2008
- Manuscript Accepted: 13 JAN 2008
- Manuscript Revised: 27 NOV 2007
- Manuscript Received: 23 AUG 2007
Digit ratio (2D:4D) may be a correlate of prenatal sex steroids, and has been linked to traits, which are influenced by fetal testosterone and estrogen. Here we consider such links in a large Internet study of sex differences (the BBC Internet Study) in which finger lengths were self-measured. Consistent with lab-based findings the 2D:4D in this study shows sexual dimorphism, ethnic differences and higher dimorphism of right 2D:4D than left, thereby indicating that 2D:4D does measure real between-participant variation. High error in self-measurement of fingers reduces effect sizes. However, the large sample size gives assurance that significant effects are likely to be real. We controlled for ethnicity and sexual orientation by considering White heterosexuals only (153,429 participants). Sexual dimorphism was confirmed in 2D:4D and for the difference of right–left 2D:4D. After Bonferroni correction we found highly significant relationships with low effect sizes as follows. In males and females there were negative associations between 2D:4D and dominance. In males there were negative associations between 2D:4D and family size and factors associated with reproductive success. For females these associations were positive. For asymmetry we found U-shaped relationships with 2D:4D in both males and females. We found no relationship between 2D:4D and promiscuity (sociosexuality). In total, we considered 48 relationships and found 29 to be significant. We compare our findings with a similar study reported by Putz et al. (2004), which found only 2 out of 57 correlations to be significant and discuss possible reasons for the discrepancies between the studies. Am. J. Hum. Biol., 2008. © 2008 Wiley-Liss, Inc.