While honesty is generally exalted in most cultures, most of us are dishonest at times, particularly if there’s an opportunity for personal gain. Stimulating the brain may counter that tendency, according to Chicago Booth postdoctoral researcher Alain Cohn, University of Zurich’s Michel André Maréchal and Christian C. Ruff, and Harvard’s Giuseppe Ugazio.

The researchers set up an experiment in which participants played a die-rolling game often used in research to determine how much people cheat. In this variation, each time players rolled the die, they had a 50 percent chance of either winning nothing or winning 9 Swiss francs (about $9). But players then decided whether to tell the truth or lie about how the die fell.

During the game, the researchers applied an electrical current to the top of participants’ skulls (transcranial stimulation) to enhance neural excitability in the right dorsolateral prefrontal cortex, a brain area that’s known to become active when people are making decisions about honesty. In another group of participants, who served as controls, the researchers passed a stimulator over people’s skulls, but shut down the current after a few seconds.

Participants in the control group reported a 68 percent success rate in their die rolls, which the researchers calculate corresponds to cheating on 37 percent of their total responses. But when the researchers applied the stimulation, the participants reported a 58 percent success rate, which corresponds to lying on just 15 percent of their responses, a significant reduction.

When a participant played the game to win money for another person instead of himself, the stimulation didn’t increase honesty as it had before: people cheated at the same rate as in the control group, which suggests that the brain area studied may be active specifically when people are behaving honestly for themselves, not for others. Further investigation revealed that the brain stimulation was likely affecting the calculation participants were making between money and honesty, rather than decreasing the value of money or increasing the value of honesty in their minds.

Though the results might one day be used in lie detection or in the rehabilitation of pathological liars, Cohn says the research goal at this point is simply to understand the neurobiology behind cheating. The findings indicate that honesty can, in principle, be externally influenced. But, he says, “it also raises the philosophical or legal question, to what extent can people be made liable for their wrongdoings?” If physiological constraints in the brain affect people’s tendency to cheat for personal gain, “we may want to rethink the extent to which we hold people accountable for their legal transgressions.”

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