Brain stimulation can control compliance with social norms

Human beings are totally dependent on a complex social structure for their survival. Since all behavior is controlled by the brain, humans may have developed specialized neural circuits that are responsible for following societal rules. A new study has identified such a region in the human brain, and researchers can increase or decrease a person’s good behavior with electrodes on the scalp that stimulate or inhibit this brain circuit.

Individuals must adhere to the rules of society, which are ultimately enforced with penalties ranging from peer criticism to severe legal penalties. “Our results suggest a neural mechanism specialized in respecting social norms,” ​​says Christian Ruff, one of the researchers of this new study published in the October 4, 2013 edition of the journal. Science. In addition to shedding light on the neurobiological basis for the evolution of social structure in humans, this new discovery suggests new therapeutic treatments for people who have problems conforming to normal social behavior. “The fact that this mechanism can be upregulated by brain stimulation indeed suggests that targeted influences on these neural processes (by brain stimulation or pharmacology) may help improve problems with social norms compliance in medical and medical settings. forensic, ”he says.

The fMRI studies already knew that neural activity increased in a specific part of the human cerebral cortex when participants conformed to social norms. This region is located in the prefrontal region of the right cerebral hemisphere, called the right lateral prefrontal cortex (rLPFC). However, a correlation between brain activity and behavior does not prove that this neural circuit causes people to conform to social norms. Such evidence would require manipulating electrical activity in this region of the brain to see if people have altered their behavior in terms of conforming to social expectations.

To test this hypothesis, the researchers designed a computerized social game in which participants had to share their winnings with a randomly assigned partner. Fairness dictates an equal distribution of earnings with the partner, but if there is no possibility of punishment for misconduct, people tend to cheat. On average, people in this study only shared 10-25% of their earnings with their randomly assigned partner if they had no recourse to punish misconduct. When the partner had the opportunity to punish the donor for unfairly sharing the winnings, players on average voluntarily complied with social norms of fairness and donated 40-50% of their winnings to the other player. .

The researchers then stimulated the participants’ rLPFC with a positively charged electrode placed on the scalp above this region of the brain, which is known to increase neural activity in the underlying tissue. Subjects then increased their transfer of gains to the other partner by 33.5%. When a negative charge of the electrode was used to decrease neural activity in this region of the brain, participants decreased fund transfer by 22.7%. “Our study shows that we can not only decrease but also increase compliance with standards with brain stimulation. It’s quite different from most of the existing studies that have primarily reported disturbances in social behavior through brain stimulation, ”says Ruff.

In the situation where there was no possibility of social sanction (punishment), brain stimulation did not have the same effect. This shows that stimulation “does not make people conform more to standards in general (it does not make them” better “). On the contrary, it makes them behaviorally sensitive to the presence / absence of threats of punishment, ”Ruff explained in an email. “This is quite important, because the theory of evolution proposes that social punishments have been absolutely crucial for the development of complex social behaviors and societal structures of humans. Without credible threats of punishment, the social order collapses very quickly. Our results establish a dedicated neurobiological mechanism that allows us to flexibly control our behavior based on the possibility of social punishment. “

Interestingly, rLPFC is not fully developed in adolescents, and people with lesions in this region may have problems controlling behavior in general and sometimes specifically during social interactions. The rLPFC integrates and coordinates activity in a large network of connections spanning many regions of the brain, so that several regions of the brain are probably cooperating in this neural circuit of fairness that binds humans together in society.


Ruff, CC, Ugazio, G. & Fehr, E. (2013) Altering Social Norm Compliance with Non-invasive Brain Stimulation. Science DOI 10.1126 / science.1241399

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Courtesy of Marc Latzel

About Marjorie C. Hudson

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