Activity in the Nucleus Accumbens and Amygdala Underlies Individual Differences in Prosocial and Individualistic Economic Choices

• Published in: Journal of cognitive neuroscience Vol. 26; no. 8; pp. 1861 - 1870
• Main Authors: Haruno, Masahiko, Kimura, Minoru, Frith, Christopher D.
• Format: Journal Article
• Language: English
• Published: One Rogers Street, Cambridge, MA 02142-1209, USA MIT Press 01.08.2014; MIT Press Journals, The
• Subjects: Adult; Amygdala - physiology; Behavior; Brain; Cerebral Cortex - physiology; Choice Behavior - physiology; Correlation analysis; Decision making; Female; Functional Neuroimaging; Humans; Individuality; Magnetic Resonance Imaging; Male; Neurosciences; NMR; Nuclear magnetic resonance; Nucleus Accumbens - physiology; Social Behavior; Social Values; Young Adult
• ISSN: 0898-929X; 1530-8898
• DOI: 10.1162/jocn_a_00589

Much decision-making requires balancing benefits to the self with benefits to the group. There are marked individual differences in this balance such that individualists tend to favor themselves whereas prosocials tend to favor the group. Understanding the mechanisms underlying this difference has important implications for society and its institutions. Using behavioral and fMRI data collected during the performance of the ultimatum game, we show that individual differences in social preferences for resource allocation, so-called “social value orientation,” is linked with activity in the nucleus accumbens and amygdala elicited by inequity, rather than activity in insula, ACC, and dorsolateral pFC. Importantly, the presence of cognitive load made prosocials behave more prosocially and individualists more individualistically, suggesting that social value orientation is driven more by intuition than reflection. In parallel, activity in the nucleus accumbens and amygdala, in response to inequity, tracked this behavioral pattern of prosocials and individualists. In addition, we conducted an impunity game experiment with different participants where they could not punish unfair behavior and found that the inequity-correlated activity seen in prosocials during the ultimatum game disappeared. This result suggests that the accumbens and amygdala activity of prosocials encodes “outcome-oriented emotion” designed to change situations (i.e., achieve equity or punish). Together, our results suggest a pivotal contribution of the nucleus accumbens and amygdala to individual differences in sociality.