Self-interest is intuitive during opportunity (in)equity: Evidence from multivariate pattern analysis of electroencephalography data.

Fairness is a remarkable preference for human society, involving both outcome and opportunity equity. Most previous studies have explored whether fairness itself or self-interest is intuitive during outcome (in)equity. However, intuition during outcome (in)equity can be affected by both fairness level and actual payoff. Since opportunity (in)equity is only affected by the fairness level, we explored only intuition during fairness by measuring event-related potential responses to opportunity (in)equity. Participants played a social non-competitive two-person choice game with advantage opportunity inequity (AI), opportunity equity (OE), and disadvantage opportunity inequity (DI). The behavioral results suggested an opportunity inequity bias, with greater feelings of fairness and pleasantness during OE than during AI and DI. However, multivariate pattern analysis of the event-related potential (ERP) data suggested that AI, OE, and DI can be significantly distinguished from each other in relatively early windows overlapping with early positive negativity (EPN), and AI and DI can be significantly further distinguished during a relatively late window overlapping with late positive potential (LPP). Moreover, the conventional ERP analysis found that EPN amplitudes were more negative for AI than for OE and DI, as well as for OE than for DI, suggesting a pleasure bias for increased self-interest. LPP amplitudes were greater for DI than for AI and OE, suggesting enhanced sensitivity to DI. These results suggest that self-interest is intuitive during opportunity (in)equity.

Give Me a Chance! Sense of Opportunity Inequality Affects Brain Responses to Outcome Evaluation in a Social Competitive Context: An Event-Related Potential Study.

People are strongly motivated to pursue social equality during social interactions. Previous studies have shown that outcome equality influences the neural activities of monetary feedback processing in socioeconomic games; however, it remains unclear whether perception of opportunity equality affects outcome evaluation even when outcomes are maintained equal. The current study investigated the electrophysiological activities of outcome evaluation in different instructed opportunity equality conditions with event-related potentials (ERPs). Participants were asked to play a competitive dice game against an opponent to win money. Opportunity equality was manipulated in three conditions, depending on whether participants were allowed the opportunity to throw less, equal, or more dice compared to their opponents. Although participants received a winning outcome with approximately 50% chance in all equality conditions, they selectively exhibited sensitivity to the less-dice condition by reporting stronger feelings of unfairness and unpleasantness than in the equal and more-dice conditions. In line with the behavioral results, larger reward positivity amplitudes were elicited by the monetary outcome in the less-dice condition than in the other two conditions, reflecting intensified reward prediction error (RPE) signals under negative emotional arousal. Further, P3 amplitudes were enhanced following reward feedback only in the unequal conditions, perhaps due to the high-level motivational and affective processing associated with resolving conflict between social norms and self-interest. The present findings elucidate the complex temporal course of outcome evaluation processes in different opportunity equality conditions.