Is digit ratio (2D:4D) different between sexual and non-sexual offenders, and non-offending men? Study of a Colombian sample

Abstract

One research line in criminal behavior studies 2D:4D ratio as predictor of aggression and violent behavior has been established, given that there are sexually dimorphic behaviors associated with the influence of testosterone on brain organization. However, results have been mixed. The aim of this study was to explore the differences in the 2D:4D ratio among offending and non-offending Colombian men in four groups (N = 139). A comparative study was conducted with three groups of offenders sentenced in a Colombian penitentiary: (1) sexual offenders against children (n = 34), (2) sexual offenders against adult women (n = 31), and (3) non-sexual violent offenders (n=26); as well as one group (4) men with no criminal record (n = 48). The 2D:4D ratio was measured using the hand scanning technique and three digital measurements were analyzed with the Autometric software: right hand ratio, left hand ratio, and difference between the right and left hand ratios (Dr -Iz). Although, in all groups, right-digit ratio was lower that left-digit ratio (negative Dr–l ratio) and, in non-offending men this difference was not significant, no strong significant differences were found between groups in any measure of 2D:4D ratio used (right hand, left hand or Dr−l). The results support the idea that these associations are too weak to consider them predictors of sexual or non-sexual criminal behavior. The risk factors determining sexual or non-sexual criminal behavior, seems to go beyond intra-uterine effects and involve complex interactions between heritability, epigenetics, and pre-natal and post-natal life events.