Lying sets up a liar’s brain to lie more

Activity in a brain region called the amygdala may explain how small lies escalate

Everyone tells a little lie once in a while. But brain activity may explain why telling lies gets easier with experience.


When small fibs snowball into blizzards of deception, the brain becomes numb to lying. As people tell more and bigger untruths, certain brain areas respond less to the whoppers, scientists now show. Their data finding might help explain how small fibs can ultimately set pants afire.

The findings “have big implications for how lying can develop,” says Victoria Talwar. She is a developmental psychologist at McGill University in Montreal, Canada. She studies how dishonest behavior develops in children. This research, she says, “starts to give us some idea about how lying escalates from small lies to bigger ones.”

Neil Garrett is a neuroscientist in England at University College London. He and colleagues there and at Duke University in Durham, N.C., performed an experiment. Their teams showed 80 participants a crisp, big picture of a glass jar of pennies. The participants were told to estimate how much money was in the jar. Then they had to share that estimate with an unseen partner. That partner, they were told, saw a smaller picture of the same jar. That meant the partner would have to rely on the participant to get a good estimate.

Each participant was serving as a “well-informed financial adviser tasked with advising a client who is less informed about what investments to make,” Garrett noted. He offered the explanation at an October 20 news briefing.

The participants didn’t have to tell their partners the truth. And the researchers gave people varying incentives to lie. In some cases, for instance, overestimating how much money was in the jar resulted in the participant getting a bigger cut of the money. That gave the estimators an incentive to stretch the truth.

As the experiment wore on, the fibs started flying. People lied the most when the lie would benefit both themselves and their unseen partner. But these “financial advisers” also told self-serving lies even when it would hurt their partner.

Twenty-five participants also underwent scans of their brains while they told lies. The researchers used a technique known as functional magnetic resonance imaging (fMRI). It estimates brain activity based on changing rates of blood flow in different parts of the brain as some task is performed. When someone had lied before, brain activity lessened in certain areas of the brain. This was most notable in the amygdala (Ah-MIG-duh-lah). A pair of these almond-shaped brain structures sit deep within each person’s brain. These areas are tightly linked to emotions.

A drop in the amygdala’s activity even seemed to predict whether someone would lie on the next trial. The findings suggest that the reduced brain activity actually influences the decision to lie.

Garrett’s group described its findings online October 24 in Nature Neuroscience.

The study design gets around a problem that can compromise other lying experiments, says Bernd Weber. He is a neuroscientist at the University of Bonn in Germany. Many experiments are based on lies that people have been instructed to say, he notes. That situation, he notes, “hardly resembles real-world behavior.” In the new study, the participants were self-motivated. They chose to play loose with the truth.

But there weren’t any real costs to a liar for a fib. The participants did not have to fear being caught. If they had been afraid, that might have altered activity in their amygdalas, Weber says. Further tests are needed to hunt for any effects of such fear.

There are plenty of examples from the worlds of finance and politics in which small lies spiraled into much bigger deceits, Tali Sharot noted in the news briefing. This neuroscientist at UCL was a coauthor of the new study. “There are many reasons why this might happen, societal reasons,” she said. “But we suspected that there might be a basic biological principle of how our brain works that contributes to this phenomenon.”

The principle she had in mind is called emotional adaptation. This is the same phenomenon that explains why the scent of strong perfume becomes less noticeable over time. The first time people cheat on their taxes, they probably feel quite bad about it, Sharot says. That remorse is good, she says. It curbs dishonesty. “The next time you cheat, you have already adapted,” she explains. Now there’s less of an emotional doubt “to hold you back, so you might be lying more.” In other words, the more someone lies, the easier it may get.

Laura Sanders is the neuroscience writer at Science News. She holds a Ph.D. in molecular biology from the University of Southern California.

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