In their article entitled "Sex Hormones and Finger Length: What Does 2D:4D Indicate?," Putz et al. reported their investigation of the relationships between three measures (left hand, right hand and mean) of the ratio of the lengths of second and fourth manual digits (2D:4D) and sex-hormone-related variables. Apart from the following variables that had been found to be related to 2D:4D in previous studies– "sexual orientation, spatial ability, status, physical prowess and components of reproductive success" (Putz et al. 187), additional variables were also examined – "voice pitch, sociosexuality, mating success and fluctuating asymmetry" (Putz et al. 187). The remainder of this paper offers a concise summary of the findings of their studies.
Corresponding to previous findings, Putz et al. found significant sex differences for the two measures of 2D:4D (left hand and right hand) and the dependent variables (such as mental rotation tests and sociosexuality scores) among male and female subjects aged between 18 and 30 (187, 192). Nonetheless, the results indicated that 2D:4D was not a particularly useful predictor of sex-hormone-mediated traits assessed in this study. Of the 57 correlations, only the left hand measure of 2D:4D was found to be significantly correlated with sexual orientation for both the male and female participants in the predicted direction (Putz et al. 195). To address the lack of correlations between the 2D:4D measures and the sex-hormone-mediated traits in the findings, Putz et al. suggested that the fluctuations of the sex hormone levels at different times of human growth and development might have affected the validity of the measurement of the traits. In other words, the disparities between the sexual differentiation in the sex-hormone-mediated traits and the timing of the sexual differentiation of the 2D:4D measures, in terms of the timing and the uniqueness of individual development, might have acco...