Brain Stimulation Can Boost Honesty, Limit Selfish Feelings


Zapping a person’s brain with an electrical current may stimulate honesty, suggests a new study that sheds light on the largely unstudied juncture between truth-telling and self-interest.

Credit: Marina del Castell/Flickr, CC BY 2.0

Researchers from the University of Stockholm in Sweden had study participants roll a regular, six-sided die 10 times and input the results of the die roll into a computer. Depending on the number that turned up, people could gain a reward of about $9 per roll – or about $90 total.

Because the participants entered the results of the die-rolling anonymously, they could decide to report the actual result or make it up.

“Most people seem to weigh motives of self-interest against honesty on a case-by-case basis; they cheat a little but not on every possible occasion,” said Michel Marechal, professor for Experimental Economics at the University of Zurich.

About 8 percent of people cheated at every opportunity in order to increase their monetary bonus, according to the study. But the incidence of cheating was not the only takeaway.

The rDLPFC area of the brain is highlighted in red. Credit: NIH

While the study participants took part in the die-rolling test, the researchers monitored their neural activity and applied a light stimulation over a portion of the brain known as the right dorsolateral prefrontal cortex (rDLPFC). The electric current “makes brain cells more sensitive” and prompts them to be more active, according to the researchers.

People who received the transcranial current on the rDLPFC region of the brain were less likely to cheat than people who didn’t receive the brain stimulation.

“This finding suggests that the stimulation mainly reduced cheating in participants who actually experienced a moral conflict, but did not influence the decision making process in those not in those who were committed to maximizing their earnings,” explained Christian Ruff, a professor of Neuroeconomics with the university.

Digging Into the Unknown

“Despite its importance, remarkably little is known about the neurobiological mechanisms supporting honest behavior,” report the authors in the journal Proceedings of the National Academy of Sciences.

The authors note that dishonesty is the cause of many known social ills and inequities, despite the lack of scientific study into its potential causes and cures. “For example, illegal tax evasion is thought to account for over 5% of the world’s gross domestic product, and total bribes to public officials are estimated at over US $1 trillion annually,” they report.

Whether someone decides to cheat comes down to a complex interplay of behavior, both inherited and learned, say the researchers. “These brain processes could lie at the heart of individual differences and possibly pathologies of honest behavior,” said Christian Ruff.

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“If breaches of honesty indeed represent an organic condition, our results question to what extent people can be made fully liable for their wrongdoings,” noted Marechal. 

Because the link to being honest resides in a specific part of the brain, the authors believe that human evolution has played a part in the ability to put truth-telling ahead of one’s own interests. The honesty-related “neural processes are functionally independent of other forms of behavioral trade-offs,” write the researchers.

“Such specialization suggests a dedicated neurobiological process that enables humans to resist the self-interested temptation to cheat, consistent with proposals that complex social structures in primate groups have led to the evolution of neural processes dedicated to the control of social behavior,” they report.

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