2D:4D Ratio and its Relation to Aggression in Athletic Students Who Play Contact Sports.

Abstract

Background: Digit ratio is calculated by dividing the length of the index finger (second digit, 2D) be the length of the ring finger (fourth finger, 4D). Positive relationships have been demonstrated between 2D:4D ratio and the level of testosterone individuals are exposed to prenatally in the womb, which is a sexually dimorphic trait. Aggression is also correlated with 2D:4D ratio, as a biological marker of high prenatal testosterone exposure. As contact-based sport is also associated with aggressiveness, it was hypothesised that a relationship would occur between low digit ratio and aggression in a population of participants involved in contact sport. Methods: A total of 44 QMU undergraduate students (contact n=21, non-contact n=21) participated in this study. All students were asked to complete Buss and Perry's Aggression Questionnaire (AQ). Aggression was measured using a 'Total Aggression Score' and on each sub-category of the AQ to include 'Anger', 'Verbal', Hostility' and 'Physical'. Second and fourth digit lengths were measured using digital callipers and the 2D:4D ratio was calculated. Data was recorded on Microsoft Excel and analysed using SPSS. Results: The results revealed a positive correlation with 'Physical' aggression and 2D:4D ratio on the dominant hand in the non-contact sports group (p = 0.04). Results from this study did reveal there was no significance in aggression scores between groups however there was a trend indicating that the contact sports group exhibit higher aggression levels. Discussion: In part, these results do strengthen the use of 2D:4D as a predictor for the effects of testosterone in utero and human behaviour, particularly for 'Physical' aggression. Although the results are not consistent with the hypothesis that the contact sports group would reveal correlations between low digit ratio and aggressiveness. Key Words: 2D:4D Ratio; Aggression; Testosterone; Prenatal Sex Hormones; Buss and Perry Questionnaire