ERP correlates of social conformity in a line judgment task

Abstract

Background: Previous research showed that individuals have a natural tendency to conform to others. This study investigated the temporal characteristics of neural processing involved in social conformity by recording participants' brain potentials in performing a line judgment task. After making his initial choice, a participant was presented with the choices of four same-sex group members, which could be congruent or highly or moderately incongruent with the participant's own choice. The participant was then immediately given a second opportunity to respond to the same stimulus.

Results: Participants were more likely to conform to the group members by changing their initial choices when these choices were in conflict with the group's choices, and this behavioral adjustment occurred more often as the level of incongruence increased. Electrophysiologically, group choices that were incongruent with the participant's choice elicited more negative-going medial frontal negativity (MFN), a component associated with processing expectancy violation, than those that were congruent with the participant's choice, and the size of this effect increased as the level of incongruence increased. Moreover, at both levels of incongruence, the MFN responses were more negative-going for incongruent trials in which participants subsequently performed behavioral adjustment than for trials in which they stuck to their initial choices. Furthermore, over individual participants, participants who were more likely to conform to others (i.e., changing their initial choices) exhibited stronger MFN effect than individuals who were more independent.

Conclusions: These findings suggest that incongruence with group choices or opinions can elicit brain responses that are similar to those elicited by violation of non-social expectancy in outcome evaluation and performance monitoring, and these brain signals are utilized in the following behavioral adjustment. The present research complements recent brain imaging studies by showing the temporal characteristics of neural processing involved in social conformity and by suggesting common mechanisms for reinforcement learning in social and non-social situations.

Figure 1

Sequence of events in a single trial.

Figure 2

The rate of making behavioral adjustment (i.e., making a response different from the initial one) in the second presentation of the line stimulus, depicted as a function of the incongruence level. Error bars represented standard errors of the means.

Figure 3

(A) ERP responses at the midline Fz, FCz, Cz, CPz, and Pz, time-locked to the onset of the presentation of group choices and categorized by level of incongruence. The shaded 250–350 ms window was for the calculation of the mean amplitudes of the MFN responses; (B) ERP responses at the midline Fz, FCz, Cz, CPz and Pz, time-locked to the onset of the presentation of incongruent group choices and categorized by subsequent behavioral tendency (change vs. no change), clasping over the highly and moderately incongruent conditions. The shaded 250–350 ms window was for the calculation of the mean amplitudes of the MFN responses.

Figure 4

(A) topographic maps for the MFN effects evoked by group choices, categorized by level of incongruence; (B) topographic maps for the MFN differences evoked by incongruent group choices, categorized by behavioral tendency (change vs. no change).

Figure 5

(A) mean MFN responses in the “change” and “no change” trials for the high vs. low conformist group; (B) Correlation between the individual index of conformity and the MFN difference between “change” and “no change” trials, clasping over the highly and moderately incongruent conditions.