Association between second to fourth digit ratio and personality among Indian men

To examine the relationship between the personality domains with the second to fourth digit ratio (2d:4d); a prenatal testosterone exposure marker.

The 2d:4d for both hands was measured for the Indian male subjects' (n = 994). Ten-item personality inventory and displaced aggression questionnaire data were collected in a self-reported proforma in this cross sectional study with a convenient sampling approach.

The personality traits, namely openness to new experiences, carelessness, and self-discipline were significantly differed between lower-half and higher-half of 2d:4d by median split. The right hand 2d:4d was positively correlated with open to new experiences and negatively correlated with disorganization, carelessness, and revenge planning. The left hand 2d:4d was positively correlated with aggression. On binary logistic regression, openness was positively associated while carelessness was negatively associated with the right hand 2d:4d and self-discipline trait was negatively associated with the left hand 2d:4d.

This study affirmed the link between 2d:4d and domains of Big Five personality factors among Indian men and inverse relationship between 2d:4d and more "female" hands in the domains of disorganization, carelessness, and revenge planning even in men, emphasizing the effect of prenatal testosterone exposure on human personality.