Lack of correlation between 2D:4D ratio and assertiveness in college age women

The ratio of the second and fourth digits of the human hand (2D:4D ratio) is an indirect measure of prenatal exposure to testosterone, with a lower ratio indicating higher exposure (Manning, 2002). Based on a previous report by Wilson (1983) that women with low 2D:4D ratios were more likely to describe themselves as assertive, we examined the correlation between 2D:4D ratio and score on the Rathus Assertiveness Schedule (RAS, Rathus, 1973). While Wilson (1983) depended on self-reports of finger length and used a chi-square analysis that did not quite reach statistical significance, we measured finger length from photocopied hands and used a parametric statistical analysis by the Pearson product correlation coefficient. We recruited 70 female college age participants without history of injury to the right hand, administered the RAS and then calculated 2D:4D ratio based on measurements taken from photocopies of the participants’ right hands. Unlike Wilson (1983), we found no significant relationship between digit ratio and assertiveness, r(68) = −0.0128, p > 0.05. Our findings suggest that variations in prenatal exposure to testosterone within the normal phenotypic range during the period of 2D:4D differentiation have little to no effect on assertiveness in women.