Criminality and the 2D:4D Ratio

Abstract

A decade old theory hypothesizes that brain exposure to androgens promotes involvement in criminal behavior. General support for this hypothesis has been provided by studies of postpubertal circulating levels of testosterone, at least among males. However, the theory also predicts that for both genders, prenatal androgens will be positively correlated with persistent offending, an idea for which no evidence currently exists. The present study used an indirect measure of prenatal androgen exposure—the relative length of the second and fourth fingers of the right hand (r2D:4D)—to test the hypothesis that elevated prenatal androgens promote criminal tendencies later in life for males and females. Questionnaires were administered to 2,059 college students in Malaysia and 1,291 college students in the United States. Respondents reported their r2D:4D relative finger lengths along with involvement in 13 categories of delinquent and criminal acts. Statistically significant correlations between the commission of most types of offenses and r2D:4D ratios were found for males and females even after controlling for age. It is concluded that high exposure to androgens during prenatal development contributes to most forms of offending following the onset of puberty.