The ratio of index to ring finger length (2D:4D) is used as a proxy for prenatal sex hormone exposure. It has been hypothesised to correlate with religiosity, though no published research has explored this possibility. Here, we initially examined 2D:4D in relation to self-reported religious affiliation and questionnaire measures of general religiosity, spirituality, religious fundamentalism, and religious commitment in male (N = 106) and female (N = 105) university students (Study 1). Although no significant correlations were observed between 2D:4D and the questionnaire measures, females who affiliated with organised religions had higher right and left hand digit ratios compared to agnostic or atheist females. Study 2 attempted to replicate these findings in an adult general population sample (N = 172 males, N = 257 females), but did not observe significant effects in either sex. Overall, these findings suggest that high 2D:4D may be relatively-specifically associated with increased religious affiliation in young, highly-educated, females.This work was supported by a Student Research Grant from the European Human Behaviour and Evolution Association (EHBEA), and an Experimental Psychology Society (EPS) Grindley Grant awarded to GR. The work was partially undertaken within the Medical Research Council UK Centre for Neuropsychiatric Genetics and Genomics (MR/L010305/1). The funders played no role in study design, data collection, analysis and interpretation, writing of the manuscript, or the decision to submit the article for publication
