Neural representations of vicarious rewards are linked to interoception and prosocial behaviour

From ‘likes’ on social media, to seeing other people eat in a restaurant, every day we constantly observe other people receiving rewards. Theoretical accounts posit that vicarious processing of these rewards might be linked to people’s sensitivity to internal body states (interoception) and facilitates a tendency to act prosocially to obtain positive outcomes for others. However, the neural processes underlying the links between vicarious reward processing, interoception and prosocial behaviour are poorly understood. Previous research has linked vicarious reward processing to the anterior cingulate gyrus (ACCg) and the anterior insula (AI). Can we predict someone’s tendency to be prosocial, or their propensity to be aware of interoceptive signals, from variability in how the ACCg and AI process other people’s rewards? Here, participants monitored rewards being delivered to themselves or an anonymous stranger during functional magnetic resonance imaging (fMRI). In a separate session, they performed a task measuring their willingness to be prosocial and exert effort to obtain rewards for others, and a task measuring their propensity to be aware and use interoceptive signals. Using multivariate similarity analysis, we show that people’s willingness to be prosocial is predicted by greater similarity between self and other representations in the ACCg. Moreover, greater dissimilarity in self-other representations in the AI is linked to a greater interoceptive propensity. These findings highlight that vicarious reward representations are linked to bodily signals in AI, and foster prosocial tendencies through the ACCg, with such information represented when simply seeing stimuli that indicate other people’s rewards. Significance Statement Every day we see other people receiving rewards. Theories suggest that how we think about these stimuli is linked to our tendency to help others (prosociality), and how strongly we rely on bodily (interoceptive) signals to guide behaviour. Can we predict someone’s degree of prosociality, or propensity to be aware of interoceptive signals, from how similarly their brain processes other people’s rewards to their own? Here, we show that responses in the anterior cingulate cortex and anterior insula when simply being told that an anonymous other person or oneself is receiving rewards, can predict how prosocial someone is and their level of interoceptive propensity, respectively. Simply viewing others’ getting rewarded fosters prosociality and varies with bodily signals. ### Competing Interest Statement The authors have declared no competing interest.