The behavioral and neural signatures of distinct conceptions of fairness

Adhering to standard procedures (impartiality), returning favors (reciprocity) or giving based on individuals' needs (charity) may all be considered moral and/or fair ways to allocate resources. However, these allocation behaviors may be perceived as differently motivated, and their moral evaluation may make different demands on theory of mind (ToM) - the capacity to process information about mental states, including motives. In Studies 1 and 2, we examined participants' moral judgments of allocations based on (1) impartiality, (2) reciprocity, (3) charity and (4) unspecified criteria as depicted in vignettes, as well as participants' perceptions of allocators' motivations. In Study 3, we used functional magnetic resonance imaging to investigate how brain regions for ToM were recruited during moral evaluation of the same vignettes. Reciprocity and charity were processed similarly, in that they recruited ToM regions to the same extent, i.e., precuneus, dorsal and ventral medial prefrontal cortex and left temporoparietal junction (LTPJ). In turn, impartiality and the unspecified condition were processed similarly, recruiting the same ToM regions to a lesser extent. Nevertheless, reciprocity elicited greater activity relative to impartiality and unspecified in the ToM regions of interest. Overall, evaluations of different allocation behaviors depend differently on ToM, with charity and reciprocity eliciting greater attention to individuals' unique states and motivations.