Oxford, J., Ponzi, D., & Geary, D. C. (2010). Hormonal responses differ when playing violent video games against an ingroup and outgroup. Evolution And Human Behavior, 31(3), 201-209. doi:10.1016/j.evolhumbehav.2009.07.002

For 14 teams of three young men, salivary testosterone and cortisol were assessed twice before and twice after competing in within-group and between-group video games that simulated violent male–male competition. Men who contributed the most to their teams’ between-group victory showed testosterone increases immediately after the competition, but only if this competition was played before the within-group tournament. High-scoring men on losing teams did not show this immediate effect, but they did show a delayed increase in testosterone. In contrast, high-ranking men tended to have lower testosterone and higher cortisol during within-group tournaments. The results are consistent with the hypothesis that men’s competitive testosterone response varies across ingroup and outgroup competitions and is muted during the former. The testosterone response during the between-group competition also suggests that violent multiplayer video games may be appealing to young men because they simulate male–male coalitional competition. (PsycINFO Database Record (c) 2012 APA, all rights reserved)