Examination marks of male university students positively correlate with finger length ratios (2D:4D).

Intersexual and intrasexual variation in second to fourth digit length (2D:4D) in humans may result from differential exposure to fetal testosterone. 2D:4D predicts several physiological, psychological and performance traits in adulthood. These relationships may reflect the 'pleiotropic' effects of testosterone on development of digits and diverse organ systems, which are expressed in adulthood. We hypothesized that 2D:4D also predicts academic success of students. 2D:4D of right hand positively predicted examination marks of males from two three-year degree courses (TYDCs). Marks of females did not covary with 2D:4D. Males from the two TYDCs differed in 2D:4D. The present results thus add to the rapidly accumulating literature on 2D:4D showing correlations with phenotypic traits in humans. If testosterone affects 2D:4D and intellectual performance, our results suggest that testosterone levels are under stabilizing selection because of effects on performance traits documented in previous studies and antagonistic effects on intellectual performance (present study).