Downregulation of the Posterior Medial Frontal Cortex Prevents Social Conformity

Abstract

We often change our behavior to conform to real or imagined group pressure. Social influence on our behavior has been extensively studied in social psychology, but its neural mechanisms have remained largely unknown. Here we demonstrate that the transient downregulation of the posterior medial frontal cortex by theta-burst transcranial magnetic stimulation reduces conformity, as indicated by reduced conformal adjustments in line with group opinion. Both the extent and probability of conformal behavioral adjustments decreased significantly relative to a sham and a control stimulation over another brain area. The posterior part of the medial frontal cortex has previously been implicated in behavioral and attitudinal adjustments. Here, we provide the first interventional evidence of its critical role in social influence on human behavior.

Modulation of Social Influence by Methylphenidate

“…The task (Figure 1) was similar to that described previously (Klucharev et al, 2009(Klucharev et al, , 2011Zaki et al, 2011). Subjects rated 153 female faces with moderate smile and attractiveness on a scale from 1 (not at all) to 8 (very), for how 'trustworthy' they believed the owner of the face to be.…”

“…Subtraction of subject ratings from the social norm resulted in our independent variable of 'social conflict' for each face. To enable comparisons with neuroimaging studies that used similar tasks (Klucharev et al, 2009(Klucharev et al, , 2011Zaki et al, 2011), we used the same five social conflict conditions as those studies. Subjects could be in 'no conflict' (NC) (within 1, including zero), moderate social conflict (À2, + 2), or high social conflict (À3, + 3) with the social norm.…”

“…Because MPH enhances reinforcement saliency in healthy adults and makes behavior of patients more acceptable to one's peers and authority figures, we anticipated that the effect would be to increase conformity. We adapted a task shown to be sensitive susceptibility to social influence (Klucharev et al, 2009(Klucharev et al, , 2011Zaki et al, 2011) to test for the effect of MPH on conformity of trustworthiness-ratings of faces.…”

Social influence and the brain: persuasion, susceptibility to influence and retransmission

“…Second, techniques such as TMS and tDCS can provide stronger evidence for causal relationships (i.e., regions or network nodes that are not only involved but necessary for influence to occur) [19,62]. In addition, taking advantage of alternative neuroimaging tools such as functional near-infrared spectroscopy can allow researchers to capture neural mechanisms of more natural, live social interactions, allowing for greater external validity of findings [63].…”

“…To further test the causal role of brain regions hypothesized to be involved in conflict monitoring and detection in social influence, researchers used transcranial magnetic stimulation (TMS) to downregulate the posterior medial frontal cortex (pMFC), overlapping with dACC, during a social influence task. This manipulation reduced conformity to social influence, possibly by interrupting key processes relevant to reinforcement learning, and hence social conformity [19].…”