Computational and Neurobiological Substrates of Cost-Benefit Integration in Altruistic Helping Decision

Although altruistic behaviors, e.g., sacrificing one's own interests to alleviate others' suffering, are widely observed in human society, altruism varies greatly across individuals. Such individual differences in altruistic preference have been hypothesized to arise from both individuals' dispositional empathic concern for others' welfare and context-specific cost-benefit integration processes. However, how cost-benefit integration is implemented in the brain and how it is linked to empathy remain unclear. Here, we combine a novel paradigm with the model-based functional magnetic resonance imaging (fMRI) approach to examine the neurocomputational basis of altruistic behaviors. Thirty-seven adults (16 females) were tested. Modeling analyses suggest that individuals are likely to integrate their own monetary costs with nonlinearly transformed recipients' benefits. Neuroimaging results demonstrate the involvement of an extended common currency system during decision-making by showing that selfish and other-regarding motives were processed in dorsal anterior cingulate cortex (ACC) and right inferior parietal lobe in a domain-general manner. Importantly, a functional dissociation of adjacent but different subregions within anterior insular cortex (aINS) was observed for different subprocesses underlying altruistic behaviors. While dorsal aINS (daINS) and inferior frontal gyrus (IFG) were involved in valuation of benefactors' costs, ventral aINS and middle INS (vaINS/mINS), as empathy-related regions, reflected individual variations in valuating recipients' benefits. Multivariate analyses further suggest that both vaINS/mINS and dorsolateral prefrontal cortex (DLPFC) reflect individual variations in general altruistic preferences which account for both dispositional empathy and context-specific other-regarding tendency. Together, these findings provide valuable insights into our understanding of psychological and neurobiological basis of altruistic behaviors.SIGNIFICANCE STATEMENT Altruistic behaviors play a crucial role in facilitating solidarity and development of human society, but the mechanisms of the cost-benefit integration underlying these behaviors are still unclear. Using model-based neuroimaging approaches, we clarify that people integrate personal costs and non-linearly transformed other's benefits during altruistic decision-making and the implementations of the integration processes are supported by an extended common currency neural network. Importantly, multivariate analyses reveal that both empathy-related and cognitive control-related brain regions are involved in modulating individual variations of altruistic preference, which implicate complex psychological and computational processes. Our results provide a neurocomputational account of how people weigh between different attributes to make altruistic decisions and why altruistic preference varies to a great extent across individuals.