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Researchers at the University of Amsterdam have discovered a neurobiological cause of intergroup conflict for the first time.

Researchers at the University of Amsterdam (UvA) have discovered a neurobiological cause of intergroup conflict for the first time. They assert that oxytocine, a neuropeptide produced in the brain that functions as hormone and neurotransmitter, leads humans to give preference to their own group and act aggressively towards competing out-groups. This finding qualifies the widespread belief that oxytocin makes people kinder and more altruistic. Their results were published today in Science.

An important qualification of this research is that oxytocine, commonly referred to as the ‘bonding hormone', arouses defensive aggression - aggression oriented towards neutralizing a threatening out-group. When the competing out-group was not considered a threat, oxytocin only triggered altruism towards one's own group. This finding provides a neurobiological explanation for the fact that conflicts between groups escalate when other groups are seen as threatening. As long as this is not the case, for example because there are (physical) barriers between the group territories, the chances of violent conflict are smaller.

The evolution of altruism in intergroup conflict

The research team at the UvA, headed by Prof. dr. Carsten de Dreu, wondered why oxytocin promotes altruistic behaviour.. Whereas classic economic theory has difficulty accounting for altruism, an evolutionary perspective suggests that altruism functions to make one's own group stronger and more effective, which also benefits the individual in the long run. Aggressive behaviour towards competing out-groups can therefore be seen as an indirect form of altruism and loyalty towards one's own group, which becomes stronger if competing out-groups grow weaker.

Charles Darwin already observed that groups whose members are altruistic towards each other and aggressive towards other groups have a greater chance of surviving than groups lacking such altruism. The researchers reasoned that if this evolutionary perpspective is true, neurobiological mechanisms should have evolved that manage altruism and aggression concurrently. The discovery that oxytocin promotes both altruism towards one's own group and aggression towards threatening out-groups supports this theory.

Publication details

C.K.W. de Dreu, L.L. Greer, M.J.J. Handgraaf, S. Shalvi, G.A. van Kleef, M. Baas, F.S. ten Velden, E. van Dijk and S.W.W. Feith, 2010. The neuropeptide oxytocin regulates parochial altruism in intergroup conflict among humans. Science (Vol. 328, no. 5984, p. 1343).

Note for editors

For more information please contact Carsten de Dreu, telephone: +21 20 525 6865, or email: UvA Press Office, telephone: +31 20 525 2695 or email: