Aggression, Digit Ratio and Variation in Androgen Receptor and Monoamine Oxidase A Genes in Men

Abstract

Variation in prenatal exposure to androgens is thought to be responsible for some of the individual differences in aggressive behavior among adults. A putative indicator of prenatal testosterone exposure, 2D:4D (the index to ring finger length) ratios have shown a weak correlation with aggression. Variation in sensitivity of the androgen receptor, resulting from polymorphism in the AR gene, is also thought to influence the relative expression of sexually dimorphic traits within each sex, including aggressive behavior and 2D:4D. Here we examine variation in aggression, 2D:4D, and polymorphism in the AR and MAO-A genes in a sample of 188 men. We find no evidence of AR gene influence on right hand 2D:4D, and a weak trend towards more feminine-typical left hand 2D:4D in men with more sensitive androgen receptors. Men with more sensitive androgen receptors tended to score lower on many of the subscales of the Aggression Questionnaire and Indirect Aggression Questionnaire. We found no influence of MAO-A allele on either digit ratio or aggressive behavior. We conclude that more masculine-typical 2D:4D does not reflect greater sensitivity to testosterone through variation in this locus on the AR gene, and that AR alleles conferring greater sensitivity to testosterone are associated with lower, not higher propensity to aggression.

Spatial abilities are not related to testosterone levels and variation in the androgen receptor in healthy young men

“…2D and E). Our results are in accordance with other studies which have not found a significant relationship between polymorphism in AR and 2D/4D ratio (Hurd et al 2010;Folland et al 2012). Further studies employing more subjects are needed to clarify these inconsistent findings.…”

Digit ratio (2D:4D) in Klinefelter's syndrome

“…Manning et al (2003) have reported that right 2D:4D and right-left 2D:4D were positively correlated with CAGn in men, and Butovskaya et al, 2012 found a similar relationship between male left 2D:4D and CAGn. These relationships were not replicated by Loehlin et al, (2011), andHurd et al, (2011) in men, but Loehlin et al (2011) reported a significant positive correlation between left 2D:4D and CAGn in women. In addition, Knickmeyer et al (2011), considering 2D:4D in newborns, reported that 2D:4D was not predicted by CAGn or by neonatal levels of testosterone, but that the interaction between CAGn and testosterone was predictive of 2D:4D.…”

Resolving the role of prenatal sex steroids in the development of digit ratio

“…In addition, high sensitivity to testosterone has been reported to be correlated with low 2D:4D (16,17). However, other studies have reported null findings with regard to correlation studies between 2D:4D and sensitivity to androgen (18) and have challenged the correlation between 2D:4D and PT (19). Clearly, we need experimental studies that do not suffer from the limitations associated with correlation data.…”