Non-invasive brain stimulation can increase honest behavior

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New research provides more clues about the brain processes involved in honesty and cheating.

“Honesty is a fundamental value in many societies,” explained one of the study’s authors, Alain Cohn of the University of Chicago. “Nevertheless, people often cheat when they can privately benefit from their dishonesty. Institutions cannot always prevent people from behaving dishonestly. Thus, we often have to rely on the intrinsic honesty of our fellow citizens.”

The study, published in the Proceedings of the National Academy of Sciences, found that honest behavior could be increased by means of non-invasive brain stimulation. The researchers found that using transcranial direct current stimulation (tDCS) to stimulate a region in the right dorsolateral prefrontal cortex (rDLPFC) made participants less likely to cheat.

“We still know relatively little about the biological basis of intrinsic honesty,” Cohn told PsyPost. “One brain imaging study (Greene and Paxton, 2009 PNAS) found that a specific area in the brain (rDLPFC) was more active when subjects pondered the trade-off between honesty and financial gain. However, the brain imaging study cannot tell us in which direction causality is running or whether the identified brain area is actually involved in this decision process or whether it is merely a byproduct. Applying tDCS allowed us to test whether the rDLPFC is causally involved when people face the trade-off between honesty and financial gain.”

The researchers used a die-rolling task to test honesty. The researchers told 145 university students to roll a six-sided die ten times for the opportunity to win 90 Swiss Francs in total. Because the participants entered their results into a computer in total anonymity, they could easily lie about whether they won money.

But the researchers could measure the amount of lying by comparing the percentage of reported successful die rolls against the statistical 50% benchmark that would be expected if everyone was honest.

“This is basic research and not meant for direct practical applications,” Cohn told PsyPost. “Our findings should be taken as a first step in identifying the brain processes that allow people to remain honest when faced with a material incentive to cheat. These brain processes could lie at the heart of individual differences in honest behavior and we show that they can, in principle, be altered through external, non-invasive interventions.

“However, it is important to note that our results suggest that such interventions may not work with pathological cheaters because in our experiments, only people who felt a moral conflict responded to the intervention. Nevertheless, our results can have implications for jurisdiction, such as to what extent people can be made fully liable for their wrongdoings.”

“The next step would be to identify the network of neural processes that are involved in decisions of honesty,” Cohn said. “The rDLPFC is most likely not the only brain region responsible for honest behavior. Our results suggest that the rDLPFC regulates the trade-off between honesty and personal material gain.”

The study, “Increasing honesty in humans with noninvasive brain stimulation“, was also co-authored by Michel André Maréchal, Giuseppe Ugazio, and Christian C. Ruffa.