Project Title
Study of aggresive and cooperative tendencies in male humans linked to testoterone levels: a new approach to provide experimental evidence under an intergroup competition scenario
Partner Organisations
Internal ID
1170513
Principal Investigator
Type
basic research

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    Item type:Publication,
    The effect of intergroup competition outcome on ingroup cooperation: insights from the male warrior hypothesis
    (2024)
    BELINCHÓN, MONTSERRAT  
    ;
    POLO RODRIGO, PABLO  
    ;
    RODRÍGUEZ SICKERT, CARLOS ANDRÉS  
    ;
    FIGUEROA VALDEBENITO, ORIANA CRISTINA  
    ;
    Nohelia Valenzuela
    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.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>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.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>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.</jats:p></jats:sec><jats:sec><jats:title>Discussion</jats:title><jats:p>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.
    Scopus© Citations 1  5
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    The Male Warrior Hypothesis: Testosterone-related Cooperation and Aggression in the Context of Intergroup Conflict
    (2020)
    José Antonio Muñoz Reyes
    ;
    N. Valenzuela
    ;
    Pablo Polo Rodrigo
    ;
    P. Pavez
    ;
    O. Ramírez-Herrera
    <jats:title>Abstract</jats:title><jats:p>The Male Warrior Hypothesis (MWH) establishes that men’s psychology has been shaped by inter-group competition to acquire and protect reproductive resources. In this context, sex-specific selective pressures would have favored cooperation with the members of one’s group in combination with hostility towards outsiders. We investigate the role of developmental testosterone, as measured indirectly through static markers of prenatal testosterone (2D:4D digit ratio) and pubertal testosterone (body musculature and facial masculinity), on both cooperation and aggressive behavior in the context of intergroup conflict among men. Supporting the MWH, our results show that the intergroup conflict scenario promotes cooperation within group members and aggression toward outgroup members. Regarding the hormonal underpinnings of this phenomenon, we find that body musculature is positively associated with aggression and cooperation, but only for cooperation when context (inter-group competition) is taken into account. Finally, we did not find evidence that the formidability of the group affected individual rates of aggression or cooperation, controlling for individual characteristics.</jats:p>
    Scopus© Citations 18  5
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    Muscularity and Strength Affect Individual Variation in Self-Perception of Fighting Ability in Men
    (2019)
    José Antonio Muñoz Reyes
    ;
    Pablo Polo Rodrigo
    ;
    RODRÍGUEZ SICKERT, CARLOS ANDRÉS  
    ;
    Paula Pavez
    ;
    Nohelia Valenzuela
    Scopus© Citations 17  8