New research finds little lies pave the way for big ones.

The study, published Monday in the journal Nature Neuroscience, is the latest addition to the catalog of scientific findings that make many people think, "Well yeah, we knew that." (Other examples include the findings that sugar makes bees hyper, that holiday food makes us fatter and that not many people read online service contracts, all of which led to a collective "Duh.")

But testing the truth of what appears obvious is kind of what science is all about, and the latest study, conducted by researchers from University College London and Duke University, set out to test whether telling small lies really did pave the way for telling larger ones.

As they put it in the introduction to their paper:

"Many dishonest acts are speculatively traced back to a sequence of smaller transgressions that gradually escalated. From financial fraud to plagiarism, online scams and scientific misconduct, deceivers retrospectively describe how minor dishonest decisions snowballed into significant ones over time. Despite the dramatic impact of these acts on economics, policy and education, we do not have a clear understanding of how and why small transgressions may gradually lead to larger ones."

To test whether little lies led to bigger ones, the researchers had 55 people look at pictures of jars full of pennies, and asked them to tell a partner how much money was in the jar. In some scenarios, they adjusted the incentives such that people would be rewarded for lying about how much money was in the jar — for example, they would get to keep the difference between what they said and what their partner said.

While that was happening, the researchers scanned the brains of about half the participants for activity in the amygdala region, known to process emotion.

What they found was that when people first started lying — deceiving their partner in order to benefit themselves — the amygdala showed more activity. But the more the participant lied, the less active the amygdala got.

And the magnitude of self-serving lies grew with repetition. A participant who deceived his partner for a couple pennies many times was more likely to go on to deceive his partner out of more money in later experiments.

"This experimental result is consistent with anecdotal observations of small digressions gradually snowballing into larger ones," the authors write.

Notably, participants were also willing to lie to benefit their partners, but the magnitude of those lies did not grow over time.

As for the role of the emotion-processing part of the brain, the authors speculate that it may be related to the idea of moral desensitization. "People often perceive self-serving dishonesty as morally wrong," they write. "Physiological and neurological measures of emotional arousal are observed when people deceive."

Or, as another deception researcher, Sophie van der Zee at the Free University of Amsterdam in the Netherlands, explained it to the New Scientist, "When you lie or cheat for your own benefit, it makes you feel bad. But when you keep doing it, that feeling goes away, so you're more likely to do it again."

So, if there's less of an emotional response to lying, they reason, "people may engage in more frequent and severe acts [of self-serving deception]."

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