The Second to Fourth Digit Ratio: A measure of two hormonally-based temperament dimensions

Constellations of biobehavioral traits are associated with activity in the testosterone and estrogen systems, due to fetal priming or hormonal alterations during the life course. Using these data, we developed two 14-item measures to investigate the traits associated with these hormone systems. To reach adequate internal consistency, we used participants of an Internet dating site; the final sample was 39,913 individuals. Factorial structure and correlations with several validating criteria were consistent with the hypothesis that these scales measured these neurochemical systems (Fisher, 2009; Fisher et al., in preparation). Two of these validity measures are discussed: gender loading of each scale; and degree to which members of each scale pursued particular occupations. Then we investigated the hypothesis that individuals scoring high on either of these scales also expressed a specific second to fourth digit ratio of the right hand. Individuals who reported a longer 4th finger relative to 2nd expressed high scores on the proposed testosterone scale; individuals who reported a longer 2nd finger relative to 4th or 2nd and 4th digits of equal length expressed high scores on the proposed estrogen/oxytocin scale. These data are consistent with the hypothesis that these 2D:4D ratios are artifacts of hormonal priming in utero.

Download the PDF