Scientists say they have found a part of the brain that helps us decide to be honest, even when telling a lie is more beneficial.
“We prefer to be honest, even if lying is beneficial,” said Lusha Zhu, Ph.D., the study’s lead author and a postdoctoral associate at the Virginia Tech Carilion Research Institute. “How does the brain make the choice to be honest, even when there is a significant cost to being honest?”
Previous studies have shown that brain areas behind the forehead, called the dorsolateral prefrontal cortex and orbitofrontal cortex, become more active during functional brain scanning when a person is told to lie or to be honest.
But there’s no way to know if those parts of the brain are engaged because an individual is lying or because he or she prefers to be honest, noted Dr. Brooks King-Casas, an assistant professor.
For this study, the researchers asked a different question.
“We asked whether there’s a switch in the brain that controls the cost and benefit tradeoff between honesty and self-interest,” said Dr. Pearl Chiu, an assistant professor. “The answer to this question will help shed light on the nature of honesty and human preferences.”
For their study, the researchers compared the decisions of healthy participants with decisions made by participants with damaged dorsolateral prefrontal cortices or orbitofrontal cortices.
The team, including scientists from the Virginia Tech Carilion Research Institute and the University of California at Berkeley, had volunteers decide between honesty and self-interest in an economic “signaling game.” Such games have been extensively studied in behavioral economics, game theory, and evolutionary biology.
In one game, the researchers presented participants with an option that gave them more money at a cost to an anonymous opponent, and an option that gave the opponent more money at a cost to the participant. Unsurprisingly, participants chose the option that gave them more money, the researchers reported.
In a different game, the researchers presented participants with the same options and but asked them to send a message to their opponents, recommending one option over the other. The participants either lie and reap the reward, or tell the truth and suffer a loss.
“The average person usually shows lie aversion,” Zhu said. “If they don’t need to send a message, they prefer the option that gives them more money. If they do need to send a message, they’re more likely to send a message that will benefit the other person even at a loss to themselves.
“They want to be honest, at the cost of their own wallet.”
Participants with damage in the dorsolateral prefrontal cortex were not as averse to lying as the two comparison groups, the researchers found. They were more likely to pick the practical option and were less concerned about the potential cost to self-image, the scientists noted.
In the game where no message was required, however, participants with dorsolateral prefrontal cortex damage showed the same pattern of decision-making as the comparison groups, suggesting that for each group, the tendency to give to others is the same, the researchers found.
“These results suggest that the dorsolateral prefrontal cortex, a brain region known to be critically involved in cognitive control, may play a causal role in enabling honest behavior,” Chiu said.
“People feel good when they’re honest and they feel bad when they lie,” King-Casas added. “Self-interest and self-image are both powerful factors influencing a person’s decision to be honest.”
“In past studies, participants are typically instructed by the experimenter to lie or be honest. There’s no consequence for lying; the subject is just complying,” he continued. “One of the real strengths of our study is that we’re able to see how a person’s tradeoffs change when we add in responsibility.”
Another factor in the new study, according to researchers, was if there is a measurable tradeoff to help determine when an honest person decides the benefit is worth the lie.
“We manipulated the costs and benefits of honesty to quantify the tipping point for each person,” said Chiu.
“We picked tough dilemmas where, for example, telling a lie might harm the other player one cent, whereas being honest will cost you $20. And you might decide that being seen as an honest person is worth more than $20, so you won’t lie even though it costs you, or you might decide that one cent of harm isn’t so bad.”
The new study sheds light on some longstanding hypotheses about honesty vs. self-interest, according to the researchers.
For example, the “Grace” hypothesis suggests that people are innately honest and have to control honest impulses if they want to profit. The “Will” hypothesis holds that self-interest is our automatic response.
“The prefrontal cortex is key to controlling our behavior and helps to override our natural impulses to be either honest or self-interested,” King-Casas said. “Knowing this, we can test whether ‘Grace’ or ‘Will’ is dominant.
“By including participants with lesions in the prefrontal cortex, we were able to test whether honesty requires us to actively resist self-interest — in which case disrupting the prefrontal cortex would reduce the influence of honesty preferences — or whether we are automatically predisposed toward honesty, in which case disrupting the prefrontal cortex would instead enhance honest behavior. And our results show a necessary role for prefrontal control in generating honest behavior by overriding our tendencies to be self-interested.
“Our next step will be to combine functional brain imaging with economic modeling to understand how the brain computes the tradeoff between the costs and benefits of lying,” he continued. “Then we can begin to understand the nature of honesty.”
The study was published in Nature Neuroscience.
Source: Virginia Tech