How effort-based self-interest motivation shapes altruistic donation behavior and brain responses

Prosocial behaviors are central to individual and societal well-being. Although the relationship between effort and prosocial behavior is increasingly studied, the impact of effort-based self-interested motivation on prosocial behavior has received less attention. In the current study, we carried out two experiments to examine the effect of motivation to obtain a reward for oneself on donation behavior and brain response. We observed that individuals who accumulated more money in the effort-expenditure rewards task (EEfRT) donated a lower proportion of their earnings. The sigmoid model fitted participants' choices in the EEfRT task, and the effort-reward bias and sigma parameters negatively correlated with the amount of money donated in the donation task. Additionally, the effort-reward bias and sigma parameters negatively predicted N2 amplitude during processing of charitable donation-related information. We propose that individuals who exhibit a lower level of effort-based self-interest motivation may allocate more cognitive control or attentional resources when processing information related to charitable donations. Our work adds weight to understanding the relationship between effort-based self-interest motivation and prosocial behavior and provides electrophysiological evidence.