How the brain adapts to telling lies

Posted on October 25, 2016

"Whether it’s evading taxes, being unfaithful, doping in sports, making up data or committing financial fraud, deceivers often recall how small acts of dishonesty snowballed over time," said U.C.L. neuroscientist Tali Sharot, the work's senior author. The team's findings confirm in a laboratory setting that dishonesty grows with repetition. The researchers also used brain imaging to reveal a neural mechanism that may help explain why. "We suspected there might be a basic biological principle of how our brain works that contributes to this phenomenon, called emotional adaptation," Sharot said.

In the study the researchers recruited 80 adults to participate in a task that involved estimating and advising a partner about the amount of money in a glass jar of pennies, which contained between £15 and £35 (around $18 to $43). The participants saw large, high-resolution images of the jars for three seconds and were told their partner (played by an actor) would see a smaller picture of the jar for one second. The participants were told their partner's goal was to estimate the amount with the help of the participant's advice, sent via linked computers. This allowed the researchers to record participants' estimates for each jar when they had no reason to lie. The participants were then given different instructions that provided incentives to be dishonest. Comparing estimates between the honest and dishonest situations allowed the team to measure degrees of dishonesty.

Depending on the scenario, dishonesty could benefit the participant at their partner's expense, benefit the partner at the participant's expense, benefit both or benefit either the participant or partner without affecting the other. For instance, in the first case participants were told they would be rewarded according to how much their partner overestimated the amount whereas their partner would be rewarded for accuracy. Participants were told their partner had no knowledge of these new instructions.

The team found that dishonesty increased over 60 presentations of the jar, but only when it was self-serving. Participants still lied when only their partner benefited but this dishonesty remained constant. When both parties benefited, participants lied more, suggesting they found this kind of dishonesty more acceptable. "People lie most when it’s good for them and the other person," Sharot said. "When it's only good for them but hurts someone else, they lie less." But lies only increased over time when the participant benefited, suggesting self-interest was necessary for dishonesty to escalate. "This study is the first empirical evidence that dishonest behavior escalates when it's repeated, when all else is held constant," said lead author Neil Garrett, a cognitive neuroscientist at U.C.L..

Twenty-five of the participants conducted the task in a functional MRI scanner, allowing the researchers to measure brain activity. They focused on areas of the brain previously found to respond to emotional stimulation, identified using a large database of brain-imaging results. This consisted primarily of the amygdala, a brain region known to respond to and process emotion. Activity in this area was initially high when participants lied, but declined over time during subsequent acts of dishonesty.

Importantly, larger reductions in activity predicted bigger subsequent lies. This suggests a biological mechanism that might underlie escalating dishonesty. A phenomenon called adaptation causes neural responses to repeated stimuli to decline. For instance, in the case of emotion amygdala activation in response to unpleasant images declines with repetition. A similar process may be operating here. "The first time you cheat, say on your taxes, you feel bad about it. But that's good, it curbs your dishonesty," Sharot explained. "Next time you cheat, you've already adapted. There's less of a negative reaction to hold you back - and you might lie more."

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Category(s):Antisocial personality, Other

Source material from Scientific American


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