The Ratio of the 2nd to 4th Finger Length Predicts Spatialability in Men but Not Women

On average men score higher on time-constrained tests of spatial ability than women. Both brain and behaviour are influenced by prenatal and adult exposure to gonadal steroid hormones. In humans the ratio of the 2ndto 4thfinger length (2D:4D) is a sexually dimorphic character that is lower in men than women and negatively correlated with testosterone levels. We report three independent studies from Sweden/London, Hungary and Liverpool confirming that 2D:4D is generally larger in women than men, that men obtain higher MRT scores than women, and demonstrating that 2D:4D is negatively correlated with MRT score in men but not women. We argue that this negative correlation between 2D:4D and spatial ability reflects the association between 2D:4D and prenatal, rather than adult, exposure to testosterone and conclude that testosterone exposure influences brain development leading to better performance on male-favouring spatial tasks.