oxytocin and group aggression

WorldScience | A chem­i­cal some­times called the “trust hor­mone” or “bond­ing hor­mone” be­cause of its role in so­cial rela­t­ion­ships can al­so pro­mote a type of con­flict, new re­search sug­gests.

Sci­en­tists have found that the com­pound, called ox­y­to­cin and pro­duced in the brain, leads hu­mans to sac­ri­fice their in­ter­ests for their own group while act­ing against out­side groups per­ceived as threat­en­ing.

The find­ings were pub­lished June 11 in the re­search jour­nal Sci­ence.

The re­search­ers, Carsten de Dreu of the Uni­vers­ity of Am­ster­dam and col­leagues, said the find­ings offer a bi­o­log­i­cal ex­plana­t­ion for why con­flicts be­tween groups es­ca­late when oth­er groups are seen as threat­en­ing. When such threat is low, for ex­am­ple be­cause there are phys­i­cal bar­ri­ers be­tween the group ter­ri­to­ries, con­flict es­cala­t­ion is less like­ly.

De Dreu and col­leagues con­ducted the study aim­ing to learn why ox­y­to­cin would pro­mote al­tru­is­tic be­hav­ior. Where­as clas­sic eco­nom­ic the­o­ry has trou­ble ex­plain­ing al­tru­ism, an ev­o­lu­tion­ary per­spec­tive sug­gests al­tru­ism func­tions to strength­en one’s own group, from which the in­di­vid­ual ben­e­fits in the long run.

Be­cause ag­gres­sion to­wards com­pet­ing groups may help one’s own group to be­come rel­a­tively stronger, ag­gres­sion is an in­di­rect form of al­tru­is­tic, loy­al be­hav­ior to­wards one’s own group, some bi­ol­o­gists the­o­rize.

Charles Dar­win noted that groups whose mem­bers are al­tru­is­tic to­wards their own are more likely to pros­per, to sur­vive, and spread. De Dreu’s team rea­soned that if this is true, mech­a­nisms should have evolved that sus­tain al­tru­ism to­wards the own group, and ag­gres­sion to­wards com­pet­ing oth­er groups. The new find­ings sup­port this per­spec­tive, they ar­gued.