Testosterone is associated with cooperation during intergroup competition by enhancing parochial altruism

Abstract

The steroid hormone testosterone is widely associated with negative behavioral effects, such as aggression or dominance. However, recent studies applying economic exchange tasks revealed conflicting results. While some point to a prosocial effect of testosterone by increasing altruistic behavior, others report that testosterone promotes antisocial tendencies. Taking into account additional factors such as parochial altruism (i.e., ingroup favoritism and outgroup hostility) might help to explain this contradiction. First evidence for a link between testosterone and parochial altruism comes from recently reported data of male soccer fans playing the ultimatum game. In this study high levels of endogenous testosterone predicted increased altruistic punishment during outgroup interactions and at the same time heightened ingroup generosity. Here, we report findings of another experimental task, the prisoner's dilemma, applied in the same context to examine the role of testosterone on parochial tendencies in terms of cooperation. In this task, 50 male soccer fans were asked to decide whether or not they wanted to cooperate with partners marked as either fans of the subject's own favorite team (ingroup) or fans of other teams (outgroups). Our results show that high testosterone levels were associated with increased ingroup cooperation during intergroup competition. In addition, subjects displaying a high degree of parochialism during intergroup competition had significantly higher levels of testosterone than subjects who did not differentiate much between the different groups. In sum, the present data demonstrate that the behavioral effects of testosterone are not limited to aggressive and selfish tendencies but may imply prosocial aspects depending on the context. By this means, our results support the previously reported findings on testosterone-dependent intergroup bias and indicate that this social hormone might be an important factor driving parochial altruism.

Evolving the neuroendocrine physiology of human and primate cooperation and collective action

“…Additional evidence with more salient ingroups come from Dominica, where men playing dominoes against competitors from neighbouring villages tended to have larger increases in testosterone than individuals playing against competitors from their home community [117]. A recent study found that acute increases in testosterone can increase cooperation within an in-group via increased parochial altruism when facing a potential out-group [119]. Interestingly, research conducted among Tsimané, where community membership is fluid and community-based competitions often pit men against their kin, show no evidence of a team-based winner effect [98].…”

Not on my team: Medial prefrontal cortex responses to ingroup fusion and unfair monetary divisions

“…These results also support a growing body of evidence that people are more likely to prevent outgroup members obtaining monetary rewards, relative to ingroup members. People are more likely to reject offers in the UG from outgroups, and the rejection of UG offers increases with increasing social distance to the outgroup (De Dreu et al., 2010; Everett et al., 2015; Kubota, Li, Bar‐David, Banaji, & Phelps, 2013; Mendoza, Lane, & Amodio, 2014; Reimers & Diekhof, 2015; Yamagishi & Mifune, 2016) . Behaviorally our results support such findings, underscoring the powerful effects that group membership has on the willingness to be altruistic toward others.…”

“In x Out”: Reviewing the Group Bias through the Biological Perspective

“…This effect of testosterone on human cooperation was more evident in participants with little prenatal exposure to testosterone (this was verifi ed via the 2D:4D ratio). Reimers and Diekhof (2015) recently verifi ed the role of testosterone in ingroup favoritism involving soccer fans. During the prisoner's dilemma game, players with high testosterone levels increased their ingroup cooperation when exposed to intergroup competition.…”