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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. |
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| 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). |
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