Social value orientation modulates fairness decision-making in empathic contexts: evidence from event-related potentials and neural oscillations

Fairness is essential for balancing interests and mitigating social conflict. People's rejection of unfairness is influenced by contextual factors (e.g. empathic concern) and individual traits including social value orientation (SVO). This study examines how individuals with different SVOs make trade-offs between empathic concern and fairness without involving their own interests. Participants played a modified ultimatum game, in which they made decisions on behalf of either a beneficiary of a public welfare project (empathy) or a stranger (non-empathy), choosing whether to accept or reject allocation offers. Results showed that empathy increased participants' tolerance for unfair offers, particularly among prosocials, who accepted more disadvantageous offers than proselfs did. EEG results showed that proselfs exhibited reduced N1 amplitudes in empathic conditions, reflecting attentional avoidance. Moreover, in the empathy condition, an unfairness-related MFN was observed only in proselfs. The absence of this typical MFN response in prosocials provides neural evidence for their active downregulation of unfairness aversion to prioritize the interests of empathic targets. In addition, prosocials showed stronger parietal-occipital alpha suppression and reduced P3 amplitude in empathy contexts, indicating heightened attentional arousal and greater allocation of cognitive resources. These findings highlight the crucial role of empathic concern and SVO in fairness decision-making.