Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis


Arts and Sciences



First Advisor

Dr. C. Nathan DeWall


In order to defend against outgroups, males and females respond to outgroup threat with different strategies. Specifically, males have been shown to respond to outgroup threat with increased ingroup solidarity and cooperation which is likely reflective of their ancestral role as warriors. What remains unknown is whether this cooperative warrior mindset among males not only increases ingroup prosociality, but also decreases ingroup aggression. Aggression against ingroup members under outgroup threat would likely disadvantage the ingroup by reducing the ingroup’s collective formidability. Further, prosocial motivations inhibit aggression. As such, I hypothesized that sex and outgroup threat would interact such that males, but not females, would respond to outgroup threat with reduced aggression towards ingroup members. To test this hypothesis, 41 male and 60 female participants were induced to either feel outgroup threat or no threat. All participants were then provoked by an ingroup member and then given a chance to aggress against that individual. Failing to support my hypothesis, outgroup threat did not interact with sex to predict aggression against ingroup members. This interactive effect was not further moderated by personality factors relevant to aggression. I discuss my findings in context of statistical power and the punishment of deviant ingroup members.