Political Science, Department of


Date of this Version



PNAS, April 24, 2012, vol. 109, no. 17, pp. 6479–6483; doi: 10.1073/pnas.1118653109


Individuals are willing to sacrifice their own resources to promote equality in groups. These costly choices promote equality and are associated with behavior that supports cooperation in humans, but little is known about the brain processes involved. We use functional MRI to study egalitarian preferences based on behavior observed in the “random income game.” In this game, subjects decide whether to pay a cost to alter group members’ randomly allocated incomes.Wespecifically examinewhether egalitarian behavior is associated with neural activity in the ventromedial prefrontal cortex and the insular cortex, two regions that have been shown to be related to social preferences. Consistent with previous studies, we find significant activation in both regions; however, only the insular cortex activations are significantly associated with measures of revealed and expressed egalitarian preferences elicited outside the scanner. These results are consistentwith the notion that brainmechanisms involved in experiencing the emotional states of others underlie egalitarian behavior in humans.

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