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Trust no one.

Whether it’s politicians misleading voters, athletes doping, financial managers defrauding investors, or just us destroying our relationships, lying is a big problem. So it’s probably a good idea to understand how it works.

We often talk about a “web of lies,” and how “one lie leads to another,” so it’s natural to think lies propagate through a perverse kind of logic: Maintaining the first little lie necessitates further, often bigger lies. But a recent study suggests otherwise.

It might not come as a surprise that when researchers at University College London studied how we lie, they did find “empirical evidence for a gradual escalation of self-serving dishonesty.”

“Deceivers often recall how small acts of dishonesty snowballed over time and they suddenly found themselves committing quite large crimes… Here, we set out to empirically demonstrate dishonesty escalation in a controlled laboratory setting and examine the underlying mechanism.”
—Tali Sharot, University College London

What’s surprising is they also uncovered a “neural mechanism” that actually supports habitual lying.

Sharot knew from others’ research that we feel bad — what she calls “emotional arousal” — when we lie. In one experiment, researchers gave subjects a drug that blocked those emotional signals. Sure enough, those given the drug were more likely to cheat on an exam than those given a placebo.

She also knew that when subjects are shown negative images, there is an emotional response in a part of the brain called the amygdala, which is associated with emotion. However, this response weakens when subjects view the images repeatedly.

With these studies in mind, Sharot and her team showed 80 subjects a picture of a jar of pennies, and asked them to tell a partner how many pennies were in the jar. In some cases the subjects were told they’d get money if they deceived their partner. In other cases, they were told they’d profit if they told the truth.

The researchers used a functional MRI scanner to analyze the brains of the subjects. When the first lie was told, the amygdala reacted strongly with a negative emotional response — in other words, guilt. But that response weakened with further lies. The response weakened significantly when big lies were told.

Lying creates a negative response in the amygdala, known commonly as ‘guilt.’ |TatyaniGI/Getty

“When we lie for personal gain, our amygdala produces a negative feeling that limits the extent to which we are prepared to lie,” Sharot told the Independent. “However, this response fades as we continue to lie, and the more it falls the bigger our lies become.” Sharot says this is why telling small lies can lead to a “slippery slope” of escalating deception.

What’s fascinating is that Sharot compares this to adaptive behavior — that collection of words and acts we adopt because they are useful for survival. If she’s right, we lie because it gives us an evolutionary advantage.

So does this mean, as a CNN headline reads, that “Lying may be your brain’s fault?” Maybe not. If lying’s to our evolutionary advantage, why are our brains hardwired to send us that stab of guilt when we do it? In any case, since the first lie is voluntary, we can choose whether we proceed down that slippery slope.