Behavior Genetics

, Volume 41, Issue 4, pp 543–556 | Cite as

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

  • Peter L. Hurd
  • Kathryn L. Vaillancourt
  • Natalie L. Dinsdale


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.


Aggression 2D:4D Digit ratio Humans Androgen receptor AR MAO-A 



The authors thank Bernie Crespi for generously hosting PLH’s sabbatical work in his lab, providing all equipment, materials, resources and advice required for the extractions and AR geneotyping, and to Tanja Schwander and Lisa Raeburn for their advice and assistance in the lab. Thanks also to Felix Breden and Julian Guttman and their labs for equipment. Thanks also to Shelagh Campbell and her lab for providing resources and equipment for MAO-A genotyping, and to Ran Zhuo for assistance in the lab. This manuscript benefited greatly from comments by Associate Editor Sarah Medland and two anonymous reviewers. This research was supported by an NSERC (Canada) Discovery Grants to PLH, Bernie Crespi, and Shelagh Campbell.


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© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Peter L. Hurd
    • 1
  • Kathryn L. Vaillancourt
    • 1
  • Natalie L. Dinsdale
    • 1
  1. 1.Department of PsychologyUniversity of AlbertaEdmontonCanada

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