Lies Breed Lies: Brain May Get Desensitized to Dishonesty

A person holds their fingers crossed behind their back. — (Image credit: file404/Shutterstock.com)

Dishonesty is a slippery slope: If you behave dishonestly once, you may become more likely to do so again in the future, a new study from England shows.

The reason may be that the brain grow less sensitive to self-serving dishonest behavior over time, the researchers said.

In the study, researchers asked 80 adults ages 18 to 65 to advise a second person about the amount of money in a glass jar of pennies. In several of the trials, conditions made it so that dishonesty benefited the participant. For example, researchers might promise the participants a higher reward if their partners overestimated the number of pennies in the jar. [10 Things That Make Humans Special]

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The study also offers support for the idea that the activity in the amygdala "signals aversion to acts that we consider wrong or immoral," Garrett said. In other words, whenever a person lies for personal gain, the amygdala produces a negative feeling that helps curb that act — but the more often a person lies, the more the response fades, leading to a slippery slope that may encourage an escalation of dishonest behavior.

People in the study actually lied the most when their lies benefited both them and their partners. This may be because it is easier to rationalize these lies, said Tali Sharot, the senior author of the study and an associate professor of cognitive neuroscience, also at University College London. In this condition, the amygdala did not show the same response pattern as when people lied solely to benefit themselves, she said at the news conference. [5 Interesting Facts about Human Cooperation]

Interestingly, though, the researchers found that study participants never lied as much as they could have. Participants' estimates of the value of the coins in the jar were always significantly lower than the ceiling, meaning that the individuals "always had an opportunity to lie more than they actually did," the paper said. Sharot explained that people usually lie by just a little bit, perhaps so they can still hold a relatively positive perception of themselves.

The researchers noted that one limitation of their study was that there was no feedback given to the participants when they lied. In the real world, the researchers noted, people who are caught being dishonest may be punished, and people who are honest may be praised, which may also affect their future behaviors. It's also unclear whether the findings would hold true in other populations, the researchers said.

Still, the results may have important implications for other types of decision-making, such as risk-taking or violent behavior, the researchers said. "The results show the possible dangers of regular engagement in small acts of dishonesty, perils that are frequently observed in domains ranging from business to politics and law enforcement," the scientists wrote in their findings. The study suggests that repeated small lies may pave the way for larger lies over time, the researchers said.