On relationships between digit ratio (2D:4D) and two fundamental cognitive drives, empathizing and systemizing, in Japanese sample

Degree of prenatal testosterone exposure in individuals is indexed by the biomarker, digit ratio, which is the length ratio between second and fourth digit fingers (2D:4D). Recent research has suggested a relationship between the digit ratio and individual differences in empathizing and systemizing, which are the two fundamental cognitive drives hypothesized by Baron-Cohen (2003). However, some studies on the relationship between digit ratio and empathy quotient (EQ) and systemizing quotient (SQ) have reported inconsistent results (Manning et al., 2010, von Horn et al., 2010 and Voracek and Dressler, 2006). This study examined the relationship between digit ratio and EQ and SQ in a sample of Japanese university students (174 males and 174 females, mean age = 19.6). Results showed that, on average, male digit ratio was lower than female digit ratio, and digit ratio correlated positively with scores on EQ and negatively with scores on SQ, although correlation coefficients were very low. These results suggest that the fetal testosterone level as estimated by the digit ratio is related to individual differences in adult cognitive and behavioral patterns.