Digit Ratio Predicts Spatial Memory Performance in Women

The ratio of the length of the 2nd and 4th digits of the hand is an indicator of prenatal testosterone exposure and has been shown to be a within sex correlate of various abilities, such as visuo-spatial processing in men. However, a number of studies report such links also exist in women, whilst others show no link for either sex. Using a unique paradigm that sub-divides visuo-spatial processing into a distinct subset of component skills we found a strong correlation between finger ratio and spatial memory performance specifically under stereo viewing conditions in women. We argue that the current ambiguity regarding links between digit-ratio and visuo-spatial ability is the result of a lack of clarity between the component skills recruited in different visuo-spatial tasks. Our task independently tested a subset of the component skills used in visuo-spatial tasks such as: mental rotation, cross-dimensionality processing and feature detection. Our results show that digit-ratio, a physical parameter linked to prenatal testosterone levels, indicates performance on a distinct aspect of visuo-spatial processing in women, without contradicting previous links for visuo-spatial processing in men. These results offer an explanation for the differences in previous findings linking visuo-spatial processing in both men and women.