Lying is part of our daily lives: The majority of us can't go even 10 minutes without lying.

But there's a qualitative difference between telling a small fib about someone's "nice" haircut and denying an extramarital affair to your spouse.

Society tells us that "honesty is the best policy."

So how do people become so adept at telling such huge lies?

A new study offers the first empirical evidence to answer that question. The answer is: self-interest.

The team of researchers paired 80 participants with an actor whom they believed to be another participant. Together, they had to guess how much money was in a photo of jars of pennies.

The researchers created various conditions in which there was an incentive to lie at the expense of their partner, to lie to benefit both parties, or to lie to benefit their partner but not themselves. The first two conditions were labeled as "self-serving" dishonesty.

Telling a self-serving lie, however small, makes it easier to tell increasingly larger lies, the study found.

Neil Garrett - nature.com

"A real-life example would be trying to sell a car with lots of problems and hiding that information from potential buyers," Neil Garrett, first author of the study and who was a doctoral student at University College London at the time, told ATTN:.

Dishonesty beneficial to both parties, the liar and the recipient of the lie, falls under the self-serving category, too. "For example, a real estate who lies to their client about how much their apartment is worth can rationalize it, because by being dishonest, they're going to get a higher price for their client and a higher commission as well," Garrett said.

The findings of the study suggest "the rate at which dishonesty escalates is best explained by self-interest." But why?

Neil Garrett - nature.com

According to the brain scans of participants during the experiments, dishonesty motivated by self-interest desensitizes the brain to the emotional response, which is usually a strong negative reaction, that a person feels while telling a lie.

"Telling small lies every day might seem fairly insignificant, but we should be cautious about them, because by the sheer act of repetition, they can escalate," Garrett said. Here's how The Huffington Post reported it:

"His findings align with past research that shows students who took mild beta blockers, a medication that reduces the effect of stress hormones and lowers a person’s physical reactions to fear and other negative stimuli, were twice as likely to cheat on a test than students who took a placebo."

Garrett, who is now a postdoctoral researcher at Princeton, said that the study leads to more unanswered questions, such as whether or not lying escalates over the long term and how other factors influence people to tell lies.

[h/t HuffPost]