The effect of intergroup competition outcome on ingroup cooperation: insights from the male warrior hypothesis.

Introduction: The Male Warrior Hypothesis (MWH) proposes that sex-specific selective pressures have promoted male cooperation with the ingroup members to outcompete rival groups. However, intergroup conflicts do not occur in isolation and the outcomes of previous competitions may influence group cooperativeness. Since this phenomenon is not well understood, we aimed to shed light on the effect of previous competition outcome on later cooperative behavior under intergroup conflicts. Based on the MWH, we hypothesized that repeated contests between groups could enhance ingroup cooperation, regardless of the outcome of the previous contest because status is at risk, but when competition is not present, participants would move to the symmetric equilibria. Methods: To test this hypothesis, we recruited 246 individuals organized in groups of 6 and measured cooperation using a threshold public good game over two rounds, manipulating the outcome in the first round to create groups of winners and losers. Results: Our results show that intergroup conflict scenarios promoted cooperation in both victory and defeat conditions, whereas, in the control scenario only losers increased their cooperation. Discussion: We argue that winners under the presence of an external threat may enhance in-group cooperation in order to assure their status; whereas, losers may be attempting to regain it.

The role of exogenous testosterone and social environment on the expression of sociosexuality and status-seeking behaviors in young Chilean men.

Testosterone plays an important role as a social hormone. Current evidence suggests that testosterone is positively related to sociosexuality increasing the psychological attitudes toward investing in short-term versus long-term mating and promotes status-seeking behaviors both by dominance and prestige. In addition, the social environment may play an important role in the expression of mating effort through changes in sociosexuality and status-seeking behaviors. However, the causal relationships among the mentioned variables are still debated. We employed a double-blind, placebo-controlled within-individual design, in order to test and integrate the proposed causal relationships between testosterone and social environment over short-term and long-term mating orientation and dominant and prestigious status-seeking behaviors in a sample of 95 young Chilean men. We did not find evidence that the administration of exogenous testosterone increased short-term or decreased long-term mating orientation as expected. Moreover, exogenous testosterone did not affect either aggressive or cooperative behavior failing to support the social status hypothesis. We also did not find any relationship between short or long-term mating orientation with status-seeking behaviors. Finally, we found support for the effect of social environment on sociosexual attitudes but not over status-seeking behaviors. Thus, men reported higher levels of short-term mating orientation in the presence of a woman compared to a man and no differences were found for long-term mating orientation. We argue that sociosexuality may be expressed flexibly, but contextual factors such as the presence of women seem more important than changes in testosterone levels.

Evidence of the active participation of women in the intergroup conflict based on the use of aggression and cooperation.

Intergroup conflict has been a persistent aspect of human societies since the emergence of our species. Various researchers have proposed that competition between groups has acted as a key selective force throughout human evolutionary history. Such intergroup competition for limited resources exacerbated the expression of intergroup aggression and intragroup cooperation. Furthermore, it would have a sexual dimorphism, with men demonstrating increased sensitivity to conflict threats-in order to maximize reproductive opportunities-, while women generally reject from active engagement in intergroup conflict. In the present study, we conducted behavioral experiments under controlled laboratory conditions to measure cooperation and aggression from using virtual games, specifically the Public Good Games and the Point Subtraction Aggression Paradigm, in a sample of 541 participants. We created control and experimental intergroup competition scenarios, where aggression and cooperation were necessary to increase monetary rewards. Our results shows that men modulate aggression and cooperation in the presence of intergroup conflict. In addition, our data also reveals that women cooperate more than men and display heightened levels of cooperation and aggression when confronted with intergroup conflict. These findings prompt a reevaluation of current functional theoretical models concerning the role of women in intergroup conflict and suggest that the dynamics of human aggression and cooperation may be more nuanced than previously believed.