Changing Social Norm Compliance with Noninvasive Brain Stimulation

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Science  25 Oct 2013:
Vol. 342, Issue 6157, pp. 482-484
DOI: 10.1126/science.1241399

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Conform to the Norm

Human societies have always enforced compliance with norms of acceptable behavior among their members by threatening punishment. It has been proposed that the human brain may have developed neural processes that support norm enforcement behavior and generate appropriate behavioral responses to social punishment threats. However, evidence for the neural circuitry underlying sanction-induced norm compliance in humans is limited. Using noninvasive brain stimulation, Ruff et al. (p. 482, published online 10 October) observed that alteration of the activity and excitability of the right lateral prefrontal cortex affected norm compliance, without affecting awareness of the content of the respective norms, or the expected sanctions. These alterations were much larger in a social, as compared to a nonsocial, context.


All known human societies have maintained social order by enforcing compliance with social norms. The biological mechanisms underlying norm compliance are, however, hardly understood. We show that the right lateral prefrontal cortex (rLPFC) is involved in both voluntary and sanction-induced norm compliance. Both types of compliance could be changed by varying the neural excitability of this brain region with transcranial direct current stimulation, but they were affected in opposite ways, suggesting that the stimulated region plays a fundamentally different role in voluntary and sanction-based compliance. Brain stimulation had a particularly strong effect on compliance in the context of socially constituted sanctions, whereas it left beliefs about what the norm prescribes and about subjectively expected sanctions unaffected. Our findings suggest that rLPFC activity is a key biological prerequisite for an evolutionarily and socially important aspect of human behavior.

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