title: Anterior insula signals inequalities in a modified Ultimatum Game.
abstract: Studies employing the Ultimatum Game (UG) which involves two parties (i.e., proposers and responders) splitting some money have suggested the role that anterior insula (AI) plays in detecting fairness norm violation, i.e., violation of the responder's expectation of receiving equal splits from the proposer. In this study, we explored how AI would respond when there existed simultaneously another expectation of being treated equivalently as others. Participants acted as responders and would be informed about both the offers they received and the average amount of money the same proposer offered to others. Hence we introduced different conditions where participants were treated equivalently or not equivalently as other responders in UG. Participants could decide to accept or reject the offer with acceptance leading to the suggested split and rejection leaving both parties nothing. Behavioral results showed that participants rejected more unfair offers and reacted more slowly during acceptance (vs. rejection) of offers when they were offered less than others. At the neural level, stronger AI activation was observed when participants received unfair relative to fair offers, as well as when they received unequal relative to equal offers. Moreover, dorsomedial prefrontal cortex/dorsal anterior cingulate cortex (dmPFC/dACC) exhibited greater activity during receiving unequal (vs. equal) offers and during acceptance (vs. rejection) of offers which were less than others'. Taken together, the present study demonstrated that the treatment of others modulated both behavioral responses to unfairness and neural correlates of the fairness-related decision-making process, and that AI played a general role in detecting norm violations.
authors.affiliation: Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai, China.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Shanghai Key Laboratory of Magnetic Resonance and Key Laboratory of Brain Functional Genomics, Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, East China Normal University, Shanghai, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zheng
authors.affiliation: School of Psychology and Cognitive Science, East China Normal University, Shanghai, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai, China.
authors.forename: Yijie
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Shanghai Key Laboratory of Magnetic Resonance and Key Laboratory of Brain Functional Genomics, Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, East China Normal University, Shanghai, China. Electronic address: xyguo@psy.ecnu.edu.cn.
authors.forename: Xiuyan
authors.initials: X
authors.lastname: Guo
authors.affiliation: Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai, China.
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000502:physiology*; D003657:Decision Making / Q000502:physiology*; D004644:Emotions / Q000502:physiology*; D005260:Female; D005717:Games, Experimental; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D012959:Socioeconomic Factors; D055815:Young Adult
keywords: anterior insula; expectation; fMRI; norm violation; unfairness