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Size of brain area linked to willingness to give

July 14, 2012
Courtesy of the University of Zurich
and World Science staff

The size of a small brain re­gion in­flu­ences one’s pre­dis­po­si­tion for al­tru­is­tic be­hav­ior, a study has found.

The dis­cov­ery re­veals for the first time a con­nec­tion be­tween brain anat­o­my, brain ac­ti­vity and al­tru­is­tic deeds, said Ernst Fehr of the Uni­vers­ity of Zu­rich in Switz­er­land, who led the stu­dy.

The ar­ea high­light­ed in yel­low is the junc­tion be­tween the pa­ri­e­tal and the tem­po­ral lobes. (Cred­it: U. of Zu­rich)


His team found that peo­ple who be­have more al­tru­is­tic­ally than oth­ers have more “gray mat­ter” at the junc­tion be­tween two large struc­tures called the pa­ri­e­tal and tem­po­ral lobe. Gray mat­ter is a type of brain tis­sue that con­sists of nerve cells and is gray­ish. The brain re­gion in ques­tion, called the tem­po­ro­pa­ri­e­tal junc­tion, lies ap­prox­i­mately be­hind the ear.

The sci­en­tists en­listed vol­un­teers who were asked to di­vide a pot of mon­ey be­tween them­selves and an anon­y­mous sec­ond per­son, at their own dis­cre­tion. Some were al­most nev­er will­ing to sac­ri­fice mon­ey while oth­ers acted quite gen­er­ous­ly. A sig­nif­i­cant cor­rela­t­ion be­tween the size of the tem­po­ro­pa­ri­e­tal junc­tion and gen­eros­ity be­came ev­i­dent, the in­ves­ti­ga­tors re­ported. 

A pre­vi­ous study had linked that brain re­gion to the abil­ity to put one­self in some­one else’s shoes in or­der to un­der­stand their thoughts and feel­ings, though not to al­tru­ism di­rect­ly.

The re­search­ers al­so not­ed what they called an in­tri­guing dif­fer­ence in ac­tiva­t­ion pat­terns. For stin­gi­er peo­ple, cells in the junc­tion be­came elec­tric­ally ac­tive when the cost of al­tru­is­tic be­hav­ior was very low. For gen­er­ous types, this ac­ti­vity went up only when the cost was very high. So ac­tiva­t­ion seemed to oc­cur when some­one hit the lim­it of their will­ingness to be­have al­tru­is­tic­ally, Fehr and col­leagues re­marked.

“These are ex­cit­ing re­sults for us. How­ev­er, one should not jump to the con­clu­sion that al­tru­is­tic be­hav­ior is de­ter­mined by bi­o­log­i­cal fac­tors alone,” Fehr said. So­cial pro­cess al­so in­flu­ence gray mat­ter vol­ume, he ex­plained, so the find­ings sug­gest that per­haps ap­pro­pri­ate train­ing or so­cial norms could pro­mote the de­vel­op­ment of brain re­gions im­por­tant for al­tru­is­tic be­hav­ior.


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The size of a small brain region influences one’s predisposition for altruistic behavior, a study has found. The discovery reveals for the first time a connection between brain anatomy, brain activity and altruistic deeds, said Ernst Fehr of the University of Zurich in Switzerland, who led the study. His team found that people who behave more altruistically than others have more “gray matter” at the junction between two large structures called the parietal and temporal lobe. Gray matter is a greyish type of brain tissue consisting of nerve cells. The brain region in question, called the temporoparietal junction, lies approximately behind the ear. The scientists enlisted volunteers who were asked to divide a pot of money between themselves and an anonymous second person, at their own discretion. Some were almost never willing to sacrifice money while others acted quite generously. A significant correlation between the size of the temporoparietal junction and generosity became evident, the investigators reported. A previous study had linked that brain region to the ability to put oneself in someone else’s shoes in order to understand their thoughts and feelings, though not to altruism directly. The researchers also noted what they called an intriguing difference in activation patterns. For stingier people, cells in the junction became electrically active when the cost of altruistic behavior was very low. For generous types, this activity went up only when the cost was very high. So activation seemed to occur when someone hit the limit of their willingness to behave altruistically, Fehr and colleagues remarked. “These are exciting results for us. However, one should not jump to the conclusion that altruistic behavior is determined by biological factors alone,” Fehr said. Social process also influence gray matter volume, he explained, so the findings suggest the notion that appropriate training or social norms could promote the development of brain regions important for altruistic behavior.