Social Comparison Modulates Outcome Evaluation: Neural Mechanisms of Emotional-Cognitive Processing in Gain and Loss...

People usually evaluate themselves in comparison to others, and this can occur in three directions. Upward comparisons occur when comparing oneself to a superior person, parallel comparisons occur when comparing oneself to a similar person, and downward comparisons occur when comparing oneself to an inferior person. The present study explores how social comparison influences individual decision-making and the associated neural mechanisms within gain/loss frames. Using a two-option gambling task, we created an ecologically valid social comparison scenario, implicitly manipulating the three comparison types. A total of 69 participants (aged 18-27, 37 females) were assigned to one of these three groups. Our results revealed that behavioral and subjective emotional responses differed significantly across groups. Using electroencephalography, the study also explored the neural mechanisms underlying emotional response, reflected in P2, P3, and late positive component (LPP), and cognitive responses, reflected in delta and aperiodic activity including offset and exponent. In the parallel comparison group, the LPP was enhanced for equal outcomes compared to other outcomes across both gain and loss frames, and aperiodic activities, triggered by different outcomes, depended on whether it was the gain or loss frame, indicating a "social consistency-frame adaptation" pattern. In the upward comparison group, non-advantageous outcomes elicited larger LPP than advantageous outcomes in the loss frame, while advantageous outcomes elicited greater cognitive processing than non-advantageous outcomes (delta and offset), suggesting a "non-advantageous sensitivity-cognitive overload" pattern. In the downward comparison group, an enhancement of P2-P3-LPP amplitude was elicited by advantageous outcomes in the gain frame, while disadvantageous outcomes induced greater cognitive processing than even outcomes (delta and exponent), indicating an "advantageous preference-disadvantageous reappraisal" pattern. These findings have important implications for understanding decision-making biases in social contexts and mental health problems, such as the emotional abnormalities linked to social comparison.