The association between 2D:4D ratios and sociosexuality: a failure to replicate.

Researchers investigating the role of biological factors in the development and maintenance of interest in uncommitted sexual activity (i.e., sociosexuality) have reported that greater prenatal androgen action in women, as inferred by the ratio of the 2nd to 4th digit, is associated with greater interest in uncommitted sexual relationships, as measured by scores on the Sociosexuality Orientation Inventory (SOI) (Clark, 2004). This evidence suggesting a rather extensive role for prenatal factors in human mating behavior has been cited over 20 times in the literature. However, despite this indication of the impact of the research results on theories of human sex differences, there are no published replications of the original finding. For that reason, the association between 2D:4D ratios and sociosexuality was evaluated in two studies. In the first study, using methodology similar to the original report, no significant association between 2D:4D ratios and SOI scores was found either in women (n = 25) or men (n = 25). Next, to test the possibility that moderating factors, such as menstrual cycle phase and circulating testosterone levels, influence the strength of the association between 2D:4D ratios and sociosexuality, salivary hormone levels and behaviors were measured during the early follicular and mid-luteal phase of the menstrual cycle in women not using hormonal contraceptives (n = 40) and at two time points in women using oral contraceptives (n = 44) and in men (n = 42). Women and men in this study showed the expected sex differences in hormone levels and behavior. However, circulating hormones and 2D:4D ratios were unrelated to measures of sociosexuality obtained at the two test sessions. In sum, these data suggest that factors other than prenatal and circulating hormones explain the sex differences in self-reports of sociosexuality.