Influencing the brain to increase anti-social behaviour

Researchers at the Maastricht and Bonn universities influence brain activation and subsequently increase the extent to which social norms are breached.

The ability to adapt behaviour to fit social norms and values is an important prerequisite for peaceful coexistence in human societies. Researchers at the universities of Maastricht and Bonn have now shown that the right dorsolateral prefrontal cortex in the brain guards us from violating social norms. Using Transcranial Magnetic Stimulation (TMS), they were able to inhibit the activity of this brain structure and evoke unfair behaviour and norm violation in the test subjects as a result. The results are now available in the Social Cognitive and Affective Neuroscience journal.

Getting along in human society requires people to be considerate of others and adapt their behaviour to social norms. If they only take their own welfare into account, they rapidly become outsiders. To avoid that, the majority of people adopt a fairness strategy.

For many years now, scientists have seen a correlation between fair behaviour and a brain structure called the dorsolateral prefrontal cortex, which is located in the frontal lobe. “This brain region is responsible for self control and it appears that, without self control, we lean towards self interest,” explains Arno Riedl. Riedl is one of the authors of the study and an economist at the Department of Economics at Maastricht University.

The research team, also consisting of Jörg Gross, Alexander Sack and Teresa Schuhmann from the Department of Cognitive Neuroscience of Maastricht University and researchers from Bonn University in Germany, succeeded in performing an experiment demonstrating the direct functional link between the right dorsolateral prefrontal cortex and norm-guided fair behaviour. In doing so, the research team used the scientific knowledge that people are more prepared to adhere to norms if they are otherwise threatened with consequences.

Test subjects become “dictators”

In the Maastricht University laboratory, scientists carried out an experiment called the “dictator game.” Seventeen test subjects slipped into the role of dictators: they were able to freely decide what proportion of a previously determined sum of money they wanted to share with their fellow players.

Sixty additional test subjects acted as “recipients.” This experiment was conducted in two ways: in one version, the recipient simply had to accept the decision that the dictators made. In the second variant, they had the option to punish the dictators. If they thought that the sum of money that was shared was too low, they were able to impose a financial fine on the dictator. When the dictators had no consequences to fear, they were, as expected, significantly more tight-fisted than when the “recipients” were able to punish them for their meanness.

Shortly before the test subjects played the two variants of the dictator game, the researchers inhibited the right dorsolateral prefrontal cortex in dictators using TMS. This involved using a coil to create a magnetic field from the outside through the cranial vaults of the test subjects, which can inhibit the activity of specific regions of the brain.

“This method is not dangerous for the test subjects and the effect disappears after a few minutes,” explains Schumann. When the dictators with inhibited brain regions began distributing the amounts of money, the result was clear: they behaved more selfishly and were poorer at adapting their behaviour to the impending consequences than when the right dorsolateral prefrontal cortex was active.

Selfish behaviour against better knowledge

“Despite the test subjects knowing that their unfair behaviour would lead to a fine, they were clearly unable to respond with appropriate strategies, due to the restricted activity of the inhibited brain structure,” says Riedl from Maastricht University.

Can such complex behaviour actually be traced back to a single brain structure? According to the researchers, norm-guided behaviour is an important prerequisite for functioning societies and the dorsolateral prefrontal cortex appears to be the key to that. Sack explains that there are limitations, however: “It is not yet possible to increase the activity of the brain structure in the long-term in order to promote fair behaviour.”

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