title: Equality versus self-interest in the brain: differential roles of anterior insula and medial prefrontal cortex.
abstract: Everything else being the same, an equal outcome is generally preferred; however, an equitable allocation sometimes is possible only by sacrificing the total amount of resources available to society. Moreover, direct interests may interact with the perception of equality. Here, we have investigated individual preferences, and their neural basis, by employing a task in which an allocation of a fixed amount between the subject and another person (MS condition) or two third parties (TP condition) is randomly determined. The subject can accept or reject the outcome, in the same fashion as the Ultimatum Game: thus an unequal offer may be rejected at the cost of a loss in total amount. Behavioral results show preference for equal outcomes in TP and for equal and advantageous outcomes in MS. An activation of medial prefrontal cortex (mPFC), extending to the anterior middle cingulate cortex (aMCC), was found in MS unequal outcomes, particularly for disadvantageous outcomes and consequent rejections. The anterior insula (AI) was active for unequal outcomes, in both MS and TP. We propose that the equal treatment is a default social norm, and its violation is signaled by the AI, whereas aMCC/mPFC activation, negatively correlated to rejections, reflects the effort to overcome the default rule of equal treatment in favor of a self-advantageous efficiency.
authors.affiliation: Cognitive Neuroscience Sector, International School for Advanced Studies (SISSA/ISAS), Via Bonomea 265, 34136 Trieste (TS), Italy. claudia.civai@gmail.com
authors.forename: Claudia
authors.initials: C
authors.lastname: Civai
authors.forename: Cristiano
authors.initials: C
authors.lastname: Crescentini
authors.forename: Aldo
authors.initials: A
authors.lastname: Rustichini
authors.forename: Raffaella Ida
authors.initials: RI
authors.lastname: Rumiati
mesh_terms: D003220:Conflict, Psychological; D003657:Decision Making / Q000502:physiology*; D005260:Female; D005717:Games, Experimental; D006801:Humans; D007398:Interpersonal Relations; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D012649:Self Concept; D055815:Young Adult