Investigating the relationship between 2D:4D Ratio and Aggression

Abstract

Digit ratio (2D:4D) is calculated by dividing the length of the index finger (second digit, 2D) by the length of the ring finger (fourth digit, 4D). As there is a positive relationship between left length of the fourth digit and the level of prenatal testosterone a foetus is exposed to, men are known to have a longer 4D than 2D, and thus a lower digit ratio. This trait is sexually dimorphic. High levels of testosterone are associated with increased aggression, and thus it was hypothesized that individuals with a low 2D:4D ratio would be more aggressive than those with a high ratio. A negative correlation was expected to be observed between 2D:4D and aggression. Aggression was measured on four scales as well as a total aggression score, though distribution of the Buss-Perry Aggression Questionnaire. Finger length was measured from the tip of the finger to the distal palmar crease in males and females. When data for gender was pooled (N=34), a positive correlation was observed between right hand digit ratio and anger (r=0.399, p=0.019), hostility (r=0.453, p=0.007) and total aggression (r=0.355, p=0.039). A positive correlation was also observed between these variables in an exclusively female population. This research has provided no statistical evidence of a correlation between verbal or physical aggression and 2D:4D ratio in males or females. Results from this study are not consistent with the hypothesis that a low 2D:4D ratio gives a high aggression score. Key Words 2D:4D Ratio; Digit Ratio; Aggression; Buss-Perry Questionnaire; Prenatal Sex Hormones; Testosterone.