Neuroimaging finds honesty is easier than lying

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The cognitive processes involved with honesty suggest that truthfulness depends more on absence of temptation than active resistance to temptation, according to a study to be published online this month in the Proceedings of the National Academy of Sciences.

Using functional MRI (fMRI), Harvard University psychologists looked at the brain activity of people given the chance to gain money dishonestly by lying and found that honest people showed no additional neural activity when telling the truth, implying that extra cognitive processes were not necessary to choose honesty. However, those individuals who behaved dishonestly, even when telling the truth, showed additional activity in brain regions that involve control and attention.

"Being honest is not so much a matter of exercising willpower as it is being disposed to behave honestly in a more effortless kind of way," said lead author Joshua Greene, assistant professor of psychology in the faculty of arts and sciences at Harvard in Cambridge, Mass. "This may not be true for all situations, but it seems to be true for at least this situation."

Greene, along with Joe Paxton, a Harvard graduate student in psychology, designed the study to test two theories about the nature of honesty--the Will theory, in which honesty results from the active resistance of temptation, and the Grace theory, in which honesty is a product of lack of temptation.

Using fMRI, they found that the Grace theory is accurate, because the honest participants did not show any additional neural activity when telling the truth.

To prompt participants to lie, the researchers created a cover story about the focus of their study. Participants were asked to predict the outcomes of a series of coin tosses, and were told that the researchers believed predicting the future was more likely when given a monetary incentive and when the prediction wasn't shared in advance of the outcome. This method gave the participants the opportunity to lie and claim that they had correctly predicted the coin toss to win the money.

Individuals who reported improbably high levels of accuracy were classified as dishonest, and participants reporting statistically feasible levels of accuracy were classified as honest. The researchers emphasized that the labels ‘honest' and ‘dishonest' describe only these individuals' behavior in the experiment and need not characterize their behavior more generally.

Using fMRI, Greene and colleagues found that the ‘honest' individuals displayed little to no additional brain activity when reporting their prediction of the coin toss. However, the dishonest participants' brains were most active in control-related brain regions when they chose not to lie. The control-related brain regions include the dorsolateral prefrontal cortex and the anterior cingulate cortex, and previous research has shown that these regions are active when an individual is asked to lie.

"When the honest people leave money on the table, you don't see anything special or extra going on in their brains at all," Greene said. "Whereas, when the dishonest people leave money on the table, that's when you saw the most robust control network activation."

Greene added eventually neuroscience may be possible to detect lies by looking at someone's brain activity, although a lot more research needs to be conducted in this area before anything could be said conclusively.

The research was funded by the John D. and Catherine T. MacArthur Foundation, the National Science Foundation and the Athinoula A. Martinos Center for Biomedical Imaging.