Neural correlations of the influence of self-relevance on moral decision-making involving a trade-off between harm and reward

Although economists have suggested that humans generally prioritize maximizing their own self-interest rather than others' when distributing rewards, recent psychological studies have shown that people are hyperaltruistic when allocating physical harm to themselves and others during moral decision-making. However, little is known about how the neurocognitive mechanisms underlying self-relevance modulate this behavioral tendency under different degrees of physical harm. This study adopted a moral decision-making task to investigate behavioral and neural processes during moral decision-making involving different levels of self-relevance and physical harm. Event-related potentials were measured while participants made trade-offs of different monetary gains for themselves against painful electric shocks experienced by the receivers (self, friend, or stranger). These results suggest that early anterior N1, indexing fast and automatic moral intuitional process, decreased during the strong conflict trade-off decisions involving strong painful electric shocks and much monetary gains. Lower self-relevance enhanced the aversive experience and increased the mental cost of resolving moral conflict, reflected by a larger P260-LPP (300-450 ms) effect during weaker conflict decisions toward strangers than themselves and friends. However, this effect was weaker during strong conflict decisions. When making decisions about whether to shock others to gain money for themselves, participants were hyperaltruistic, foregoing greater self-interest to restrain harm directed toward strangers than themselves or friends. These findings shed light on the neural basis of the tension between egoistic and altruistic tendencies during moral decision-making integrating benefits and harms.