Over 6 decades ago, experimental evidence from social psychology revealed that individuals could alter their responses in perceptual judgement tasks if they differed from the prevailing view emitted by a group of peers. Responses were thus modulated to agree with the opinion of the social group. An open question remains whether such changes actually reflect modified perception, or whether they are simply the result of a feigned agreement, indicating submissive acceptance. In this study, we addressed this topic by performing a perceptual task involving the assessment of ambiguous and distinct stimuli. Participants were asked to judge the colours of squares, before, and after receiving feedback for their response. In order to pinpoint the moment in time that social feedback affected neural processing, ERP components to ambiguous stimuli were compared before and after participants received supposed social feedback that agreed with, or disputed their response. The comparison revealed the presence of differences beginning already 100ms after stimulus presentation (on the P1 and N1 components) despite otherwise identical stimuli. The modulation of these early components, normally thought to be dependent on low-level visual features, demonstrate that social pressure tangibly modifies early perceptual brain processes.

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In recent years, neuroscience has begun to investigate brain responses to social stimuli. To date, however, the effects of social feedback on attentional and perceptual processes remain unclear. In this study, participants were asked to judge the hues of distinct, or ambiguously coloured stimuli, and to indicate their confidence ratings. Alleged social feedback was then provided, either endorsing or disputing the participants’ responses. Participants were then presented the stimulus a second time and given the option to reconsider their decision. Behavioural findings showed that confidence levels decreased both with task difficulty and with conflicting social feedback. Event-related potential data showed greater P2 and N2 amplitudes for ambiguous squares compared to distinct squares upon initial stimulus presentations, compatible with heightened attention. Moreover, a decreased P300 was found for ambiguous stimuli, consistent with an increase in metacognitive activity. After social feedback, an early-late positive potential between 270 and 370 ms continued to distinguish ambiguous from distinct stimuli. More importantly, after 400 ms, the late positive potential distinguished endorsed from disputed stimuli. These results reveal that social feedback, while decreasing effects linked to uncertainty, gives rise to later processes associated with enhanced motivational significance of the stimulus following divergence from social approval.