Telling lies can make the brain insensitive to dishonesty

Catch me if you can

Everyone tell small lies in daily life. Although these lies seem to be insignificant, they can gradually make the brain insensitive to dishonesty, meaning that lying gradually feels more comfortable over time.

The finding is published in Nature Neuroscience. Researchers from University College London led the study.

They are interested in a phenomenon that deceivers often recall small acts of dishonesty snowballed over time and they suddenly found themselves committing quite large crimes.

This is just like American fraudster Frank Abagnale, played by Leonardo DiCaprio in the film Catch Me If You Can, started out swindling his father out of small change for date money and ended up impersonating an airline pilot, despite the admission that he “couldn’t fly a kite”.

Researchers suspected that this phenomenon was due to changes in the brain’s response to lying, rather than simply being a case of one lie necessitating another to maintain a story.

In the study, 80 volunteers played a game in which they estimated the value of pennies in a jar and sent their guess to an unseen partner.

Sometimes participants were told they would secretly benefit at their partner’s expense if they overestimated the cash in the jar, incentivising them to lie.

Researchers knew by how many British pounds participants lied on each trial. They found that the amount by which participants lied got larger and larger.

At first, volunteers tended to alter the jar’s value by around £1, but this typically ramped up to about £8 by the end of the session.

After that, 25 of the volunteers played the game while having their brain activity monitored by an MRI scanner.

This showed that the amygdala, a part of the brain linked with emotion, was most active when people told their first lie.

But while the untruths escalated in magnitude, the amygdala’s response gradually declined. Larger drops in brain activity predicted bigger lies in future.

The researchers said this adaptation effect was similar to those seen in basic sensory experiences. A scent becomes less potent when smelt repeatedly, for instance.

They speculate that the amygdala activity could represent the internal conflict between wanting to see oneself as honest and being tempted to act in self-interest by lying.

This fits with their observation that people appeared to lie more readily in tasks where it benefited both themselves and their partner, possibly because it was easier to justify a lie that served the common good.

In addition, it shows that lying is probably a learnt behaviour. If people develop a pattern of behaviour and it’s reinforced, they will return to that habit.

An interesting question is whether there would be interventions to un-train somebody. If a person is a chronic liar, that’s really a problem for society.

Finally, there is little prospect of converting the findings into a more accurate lie detection test. In fact, the variation over time in the brain’s response to lying demonstrates how difficult it would be to come up with a universal test.

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Citation: Garrett N, et al. (2016). The brain adapts to dishonesty. Nature Neuroscience, published online. Doi:10.1038/nn.4426.
Figure legend: This image is for illustrative purposes only.