Humans resist unequal distributions of goods in their social interactions, even if it requires foregoing personal gains—Study Finds A Causal Role of the Insula in Aversion to Social Inequity Via Lesion Evidence

Lesion Evidence for a Causal Role of the Insula in Aversion to Social Inequity. Felix Jan Nitsch, Hannah Strenger, Stefan Knecht, Bettina Studer. Social Cognitive and Affective Neuroscience, nsab098, August 6 2021. https://doi.org/10.1093/scan/nsab098

Abstract: Humans resist unequal distributions of goods in their social interactions, even if it requires foregoing personal gains. Functional neuroimaging studies implicate the insula in this aversion to social inequity and in fairness-related decisions, but a causal contribution has not yet been established. We compared the responses of 30 patients with lesions to the insula on a multiple-trial version of the one-shot Ultimatum Game, a neuroeconomic social exchange paradigm where a sum of money is split between two players, to those of 30 matched patients with brain injuries sparing the insula. Insula lesion patients accepted offers of an unequal disadvantageous split significantly more often than comparison lesion patients. Computational modeling confirmed that this difference in choice behavior was due to decreased aversion to disadvantageous inequity following insula damage, rather than due to increased decision noise or non-consideration of inequity. Our results provide novel evidence that the insula is causally involved in aversion to inequity and in value-based choices in the context of social interactions.

Keywords: inequity aversion, insula, computational modeling, social decision-making, value-based choices