Neural responses underlying extraordinary altruists’ generosity for socially distant others

People typically sacrifice fewer resources for socially distant others than close others, a bias termed social discounting. But people who engage in extraordinary real-world altruism, such as altruistic kidney donors, show dramatically reduced social discounting. Why they do so is unclear. Some prior research suggests generosity toward strangers requires effortfully overcoming selfishness bias. Alternately, generosity for strangers could reflect genuinely valuing strangers’ welfare more. We tested both hypotheses in this pre-registered study. Extraordinary altruists and demographically matched controls completed a social discounting task during fMRI scanning. In addition, we tested whether an eight-week Metta meditation training would reduce social discounting in typical adults. During fMRI, participants (N=77) chose selfish or generous options benefiting others at varying social distances. Behavioral results replicated altruists’ reduced social discounting relative to controls. Neither behavioral nor imaging analyses yielded support for the possibility that extraordinary altruism reflects effortfully overcoming a selfishness bias. Instead, we identified group differences in a constellation of social brain regions, including amygdala and rostral anterior cingulate, in which activation reflects the subjective valuation of distant others’ welfare. We found no effects of Metta training on behavioral or neural responses. Our results indicate altruists are more generous to strangers because regions involved in social decision-making encode the subjective value of distant others’ welfare differently than controls. As a result, altruists genuinely value distant others’ welfare more. Interventions aimed at promoting generosity for distant others may succeed to the degree they can alter neural processes supporting the subjective valuation of distant others’ welfare