Picture recall skills correlate with 2D:4D ratio in women but not men

We analyzed sex differences in spatial and recall abilities of college students while also examining the relationship to 2D:4D ratio. The 2D:4D ratio is thought to be an indirect measure of testosterone and estrogen exposure in fetal development. Participants completed a mental rotation (MR) test, free recall tests, and placement recall tests. It was predicted and confirmed that males have lower 2D:4D ratio and higher MR scores. Additionally, females outscored males on picture free recall and picture placement. Higher scoring females on these two measures had higher 2D:4D ratios, that is, more “feminine” looking hands. The results from our study are consistent with the hypothesis that fetal hormones affect 2D:4D ratio while also directly or indirectly influencing visual recall abilities in females. The tendency of sexually dimorphic cognitive skills to correlate with 2D:4D ratio in only one sex may be typical of traits that were evolutionarily adaptive in one sex, but not maladaptive in the opposite sex.