October 3, 2013 | 2
Human beings are utterly dependent on a complex social structure for their survival. Since all behavior is controlled by the brain, human beings may have evolved specialized neural circuits that are responsible for compliance with society’s rules. A new study has identified such a region in the human brain, and researchers can increase or decrease a person’s good behavior by electrodes on the scalp that stimulate or inhibit this brain circuit.
Individuals must adhere to rules of society, which are ultimately enforced by punishments ranging from peer criticism to severe legal sanctions. “Our findings suggest a neural mechanism that is specialized for social norm compliance,” says Christian Ruff, one of the researchers in this new study published in the October 4, 2013 edition of the journal Science. In addition to illuminating the neurobiological basis for the evolution of social structure in humans, this new finding suggests new therapeutic treatments for people who have problems complying with normal social behavior. “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 to ameliorate problems with social norm compliance in medical and forensic contexts,” he says.
It was already known from fMRI studies that neural activity increased in a specific part of the human cerebral cortex when participants comply with 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 comply with social norms. Such proof would require manipulating electrical activity in this brain region to see if people altered their behavior in terms of complying with social expectations.
To test this hypothesis, the researchers devised a computerized social game in which participants were required to share their winnings with a randomly assigned partner. Fairness dictates an equal split of winnings with the partner, but if there is no possibility of punishment for misbehavior, people tend to cheat. On average, people in this study only shared 10-25% of their winnings with their randomly assigned partner if the partner had no recourse for punishing misbehavior. When the partner did have the ability to punish the donor for splitting the winnings unfairly, players on average voluntarily complied with social norms of fairness and donated 40-50% of their winnings with the other player.
The researchers then stimulated the rLPFC of participants with a positively charged electrode placed on the scalp over this brain region, which is known to increase neural activity in the underlying tissue. Subjects then increased their transfer of winnings to the other partner by 33.5%. When a negative charge from the electrode was used to decrease neural activity in this brain region, participants decreased the transfer of funds by 22.7%. “Our study shows that we can not only decrease but also increase norm compliance with brain stimulation. This is quite different from most existing studies which have mainly reported disruptions of social behavior by brain stimulation,” Ruff explains.
In the situation where there was no possibility of social sanction (punishment), brain stimulation did not have the same effect. This shows that the stimulation “does not make people comply more with norms in general (it does not make them ‘better people’). Rather it renders them behaviorally sensitive to the presence/absence of punishment threats,” Ruff explained in an e-mail. “This is quite significant, as evolutionary theory proposes that social punishments have been absolutely crucial for the development of the complex social behaviors and societal structures of humans. Without credible punishment threats, social order breaks down very quickly. Our findings establish a dedicated neurobiological mechanism that enables us to flexibly control our behavior in line with the possibility of social punishment.”
It is interesting that the rLPFC is not fully developed in teenagers and people with damage to this region can have problems in control of behavior in general and sometimes specifically during social interactions. The rLPFC integrates and coordinates activity in a broad network of connections spanning many brain regions, so multiple regions of the brain likely cooperate in this neural circuitry of fairness that binds humans together in society.
Ruff, C.C., Ugazio, G., and Fehr, E. (2013) Changing social norm compliance with noninvasive brain stimulation. Science DOI 10.1126/science.1241399
Courtesy of Marc Latzel
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