期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：5
页码：1619-1624
DOI：10.1073/pnas.1414715112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificancePeople often consider the well-being of others. However, they are more likely to be generous toward individuals they feel close to than to those they only meet sporadically. Using neuroimaging tools, we show that the decline in generosity across social distance is realized by the interplay of two brain structures--the ventromedial prefrontal cortex coding the relative appeal of a selfish or a generous option, and the temporoparietal junction modulating appeal signals of the generous outcome, depending on social distance between participant and beneficiary. Based on these findings, we developed a biologically plausible model explaining social discounting in particular, and prosocial behavior in general. Our study opens up new avenues to understand and tackle frictions arising in social networks. Most people are generous, but not toward everyone alike: generosity usually declines with social distance between individuals, a phenomenon called social discounting. Despite the pervasiveness of social discounting, social distance between actors has been surprisingly neglected in economic theory and neuroscientific research. We used functional magnetic resonance imaging (fMRI) to study the neural basis of this process to understand the neural underpinnings of social decision making. Participants chose between selfish and generous alternatives, yielding either a large reward for the participant alone, or smaller rewards for the participant and another individual at a particular social distance. We found that generous choices engaged the temporoparietal junction (TPJ). In particular, the TPJ activity was scaled to the social-distance-dependent conflict between selfish and generous motives during prosocial choice, consistent with ideas that the TPJ promotes generosity by facilitating overcoming egoism bias. Based on functional coupling data, we propose and provide evidence for a biologically plausible neural model according to which the TPJ supports social discounting by modulating basic neural value signals in the ventromedial prefrontal cortex to incorporate social-distance-dependent other-regarding preferences into an otherwise exclusively own-reward value representation.
