Understanding why people are dishonest is complicated. Theories about that have been the subject of psychology and sociology books.
But could there be a biological component at play? Recent research that focused on a specific region in our brains suggests there is.
"When we lie for personal gain, our amygdala produces a negative feeling that limits the extent to which we are prepared to lie," said Tali Sharot, an associate professor of cognitive neuroscience at University College London. "However, this response fades as we continue to lie, and the more it (fades) the bigger our lies become."
A decreased amygdala response, in other words, may help explain the "slippery slope" of lying, said Sharot, one of the authors of "The Human Brain Adapts to Dishonesty
," just published in the journal Nature Neuroscience.
When lying gets easier
The scientists involved in this research tapped Neurosynth
, a platform that culls thousands of maps of brain activity, to identify parts of the brain associated with emotion.
While the amygdala, located deep in our temporal lobes, wasn't the exclusive region highlighted, it predominated, researchers said. So when the neuroscientists set out to look at how the brain changes while lying, they focused on that region.
A study was devised in which participants were partnered with someone else and then put into a brain-imaging scanner. They were shown images of a glass jar filled with pennies and asked to advise their partners (who had a blurry image) about the amount of money in the jar -- thereby establishing a baseline.
Without telling participants to be dishonest, the researchers switched incentives. In one approach, they incentivized them to lie by saying that if they got their partners to overestimate the amounts it would entitle the participant to a bigger cut of a financial reward.
The researchers found that when dishonesty served the participants, they were more inclined to lie. The more they lied, the less their amygdala lit up.
"If someone lies repeatedly, they no longer have an emotional response when they lie," explained Sharot. "In absence of an emotional response, they feel more comfortable and lie more."
The concept, she said, isn't exclusive to emotions.
Consider this: A cold pool feels unbearable at first, and then you adapt. A woman drenched in the perfume she's worn for ages doesn't notice the smell, but strangers recoil. Gruesome photographs are less difficult to look at the second, third, fourth time around.
Similarly, small lies can desensitize our brains to the negative feelings associated with lying, which opens the door to more significant lies. And the more often we're dishonest about something, the easier it is to continue being dishonest.
Take, for instance, a person who cheats on their taxes, Sharot said. The first time, that person is likely to feel guilt-ridden, nervous or scared. Over time, the cheating gets a lot easier.
Another way to look at this
This new research, while interesting, doesn't leave neuroscientist Lisa Feldman Barrett entirely convinced.
Barrett, a professor of psychology at Northeastern University and author of the forthcoming book, "How Emotions are Made: The Secret Life of the Brain," says focusing on the amygdala as the brain's source of emotion may be misguided.
Hand-selected, meta-analyses of brain mapping data, as opposed to results spit out by Neurosynth, she says, have shown that the amygdala is not necessarily critical for emotion.
People feel emotion without changes in amygdala action, she says. In fact, even people who don't have an amygdala feel emotion. Yes, that region of the brain is often engaged during emotions -- but it also becomes engaged when something appears that is novel or simply interesting. It's associated with perception, memory and social interactions.
Barrett said she also wonders if the research results would hold outside a laboratory's doors.
"They did not reward or punish for lying, whereas there is always a payoff or risk in real life," she said. "That might cause the amygdala to maintain its engagement."
All of this said, Barrett said she doesn't doubt that habituation plays a part in lying. She just isn't sure this new research, pointing to the amygdala as the source of emotion, focuses on the correct cause.