Men Are from Mars, Women Are from Venus: 2D:4D Digit Ratio Mediates Emotion Recognition from Male Eyes in Men

Background:  according to the theory of gender differences in cognitive styles, the male brain is more preprogrammed to construct and comprehend systems based on logic rules, while the female brain is more hardwired to understand other people’s mental states and emotions. It has been suggested that androgen (especially testosterone) prenatal exposure may effect brain development towards a more male-typical cognitive style. In this regard, the ratio of the length of the index finger to the ring finger  (2D:4D digit ratio) is generally considered a measure of prenatal androgen exposure, as low 2D:4D digit ratio has been associated with high fetal testosterone.  To date, there are controversial data on the correlation between 2D:4D digit ratio and emotion recognition.

Objectives: the present study aimed to investigate the potential correlation between emotion recognition and 2D:4D digit ratio in a cohort of healthy young adults.

Methods: one hundred and fifty subjects were recruited. All participants were screened by a senior psychiatrist to exclude the presence of psychiatric disorders. Participants completed the Autism Spectrum Quotient (AQ), a measure for the identification of autistic traits in the general population, the Empathy Quotient (EQ) and The Reading the Mind in the Eye Test (RMET), both measures of empathizing.

Results:  in the entire sample, there was a significant correlation between left 2D:4D digit ratio and number of RMET correct responses. Analyzing data by gender, women showed more empathizing qualities compared to men (p<0.001) and displayed a higher number of RMET correct responses both to female and to male eyes (p<0.001). However, no significant correlation between 2D:4D digit ratio and number of RMET correct responses was observed in women. In male subjects, we observed a significant positive correlation  (p<0.01) between left 2D:4D digit ratio and number of RMET correct responses to male eyes.

Conclusions: these preliminary results are in line with the hypothesis that females outperformed males in empathizing. Interestingly, literature data reported that men have more difficulties to recognize emotional expressions in female as compared to male eyes and emotion recognition in male eyes has been associated with an increased right amygdala response. Our results may suggest that androgen priming of the brain (as expressed by 2D:4D digit ratio) might be a mediator for this effect.