Abstract:

Social comparison is a mental process through which people come to know themselves by evaluating their own abilities, attitudes, outcomes and believes in comparison with others. Previous studies found that social comparison influenced the evaluative process of the outcome in the brain. However, in all those studies, social comparison was manipulated as the comparison between the rewards of two participants, so it remains unclear whether the monetary value or the comparison affects the outcome evaluation. By dissociating the monetary value from comparison, the current study aimed to investigate how non-monetary social comparison affects the process of outcome evaluation in a cooperative task. Eighteen healthy undergraduates (10 males, 8 females) took part in the EPR experiment. Participants cooperated with a confederate to complete a gambling game on two connected computers. Each of them chucked one dice sequentially and randomly. If the numbers on the two dices totaled greater than 6 in the trail, they would win 1 yuan in the trial; if not, they would lose 1 yuan. The final reward would be portioned out equally between them. After they chucked the two dices, a “>” or “<” between their name cueing comparison feedback indicates which one get a larger number. Then a feedback screen informed about whether they win or loss. However, unknown to the participants, the feedback was independent of their performance. Trails of each conditions were equal. Both social comparison feedback and monetary feedback were included in the final statistical analyses. For FRN analysis, we measured the average amplitude in the 250-350 ms time window for the social comparison feedback and the monetary feedback. P300 amplitude was quantified as the positive peak in the time window of 300-600 ms after feedback onset. ERP results revealed that FRN and P300 were both sensitive to non-monetary social comparison. When compared with those who had a better performance, participants who got a smaller number showed a larger FRN and a smaller P300. FRN amplitude of gain was more negative than that of loss. P300 showed an opposite pattern relative to FRN. Social comparison did not affect the process of outcome evaluation of the cooperative task. These findings suggest that the encoding of social comparison occurs at the early stage of the outcome evaluation. And FRN could code not only the prediction errors for monetary reward but also the information in the social context. Our results also indicate that FRN responds to the most notable information in the current context.

Key words: social comparison, outcome evaluation, FRN, P300, ERP