Equality versus self-interest in the brain: Differential roles of anterior insula and medial prefrontal cortex Claudia Civai a, c, ⁎, Cristiano Crescentini a, b , Aldo Rustichini c , Raffaella Ida Rumiati a a Cognitive Neuroscience Sector, International School for Advanced Studies (SISSA/ISAS), Via Bonomea 265, 34136 Trieste (TS), Italy b Azienda Ospedaliero-Universitaria Santa Maria della Misericordia, Piazzale Santa Maria della Misericordia, 15 33100 Udine, Italy c Department of Economics, University of Minnesota, 1925 4th Street South 4-101, Hanson Hall Minneapolis, MN 55455-0462, USA abstract article info Article history: Accepted 16 April 2012 Available online 23 April 2012 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. © 2012 Elsevier Inc. All rights reserved. Introduction Everything else being the same, an equal treatment of individuals is widely considered a preferable outcome (Engelmann and Strobel, 2007; Messick, 1995; Skitka and Tetlock, 1992). However, the realization of a more equitable allocation of outcomes is sometimes possible only at the cost of a loss in the total amount of resources available to society. The alternative between a more equitable, but smaller, pie and a larger, but less equitable, one is widespread and problematic. It is only made even more complex by the fact that the parties involved in the decision have sometimes a direct interest in the outcome. It is therefore essential to have a good understanding of how people perceive this tradeoff, and how the direct interest interacts with the abstract principle that equality is, everything else being equal, preferable. We investigated how individuals perceive the alternative by asking subjects to decide between accepting a less equitable distribution of existing resources between two individuals or rejecting the allocation at the cost of a loss of those resources for both parties. To contrast the effect of personal interest and abstract reasoning, we employed two manipulations, one in which the subject who has to accept or reject the proposed allocation is a recipient of one of the two payments, and one in which he is not. Thus, the two manipulations pose the same problem to the decider, but they differ in the level of self-involvement. When chance makes equal treatment impossible, because the available allocation is unequal, the deciding subject has the choice between either accepting, that is accepting inequality or rejecting, which means restoring equality at the cost of a zero payment to both. A relevant number of studies from different fields addressed the issues of distributional justice and perception of equality, and the findings agree in describing equality, everything being the same, as the preferred outcome. From a psychological point of view, Messick (1995) has hypothesized that people use equality heuristically, which means that they often make decisions applying some form of the idea of equality, that may lead to more or less efficient and just allocations. Fehr and Schmidt (1999) and Bolton and Ockenfels (2000) put forward formal models describing the preferences over outcome distributions, predicting aversion for unequal payoffs. Engelmann and Strobel (2007) found experimental evidence for perfect equality as a focal point, when there is no other reason to give an advantage to any person and there are no substantial costs in terms of efficiency. Neuroscientific findings support the idea that equality and fairness are the preferred distribution: Tabibnia et al. NeuroImage 62 (2012) 102–112 ⁎ Corresponding author at: Department of Economics, University of Minnesota, 1925 4th Street South 4-101, Hanson Hall Minneapolis, MN 55455-0462, USA. Fax: + 39 040 3787615. E-mail addresses: claudia.civai@gmail.com (C. Civai), crescent@sissa.it (C. Crescentini), aldo.rustichini@gmail.com (A. Rustichini), rumiati@sissa.it (RI. Rumiati). 1053-8119/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2012.04.037 Contents lists available at SciVerse ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg