You, Illuminated

Commonsense explanations of neuroscience

How to Tell a Lie

Uncovering the moral center of the brain

A friend recently told me a story about how, as a gesture of goodwill, she baked her roommate's favorite dessert. She got hold of the recommended recipe, went to the store to purchase sugar, flour, fresh strawberries and a few other ingredients, and set to work in the kitchen for the rest of the afternoon before plucking the gooey, fruit-filled confection from the oven. I can only imagine how proud she must have felt when presenting the finished product, looking just like the picture in the recipe book. After tasting the first few morsels, her roommate confessed, "It's not as good as what I'm used to," and declined an offer for seconds. This tale puts a question mark to the oft-heard expression: Is honesty really the best policy?

As a culture, we laud truth-tellers. From an early age we're taught to revere two of our most noteworthy presidents, Honest Abe and George Washington, who could not tell a lie. What does it indicate, though, when the well-known story about the first US president coming clean after cutting down his father's cherry tree is nothing more than fiction, a bold-faced lie? Certainly, there are occasions where telling the truth, plain and simple, is the appropriate thing to do, such as when under oath. But let's be honest, lying, by embellishment or fabrication, is something we do as part of our everyday lives; it's part of being human. By acknowledging our deceit, we may learn something about our nature.

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Recent studies in neuroscience have sought to understand what happens in our brains when we fib. One of the most remarkable results is that we are finally developing reliable lie-detectors. Although the polygraph has been a helpful tool, good liars are able to beat it. Prevaricators often exhibit poor eye-contact, but sometimes a person is simply nervous. Using fMRI to observe brain activity, scientists can detect lies with greater than 90% accuracy. The reason is that lying requires more brain power.

Pundits noted long ago that telling the truth is easier than lying because you don't have to remember what you said to keep your story straight. As it turns out, deception is a complicated mental task, and it requires greater brain activation than truthfulness in several key brain regions, such as the prefrontal cortex and anterior cingulate cortex. While the prefrontal cortex, what is evolutionarily-speaking the most advanced region of the human brain, plays roles in short-term memory, social conduct, decision-making and planning, the anterior cingulate cortex serves emotional functions and helps us empathize with others. It's no wonder that brain regions essential for empathy, planning, short-term memory and social conduct are active when lying. To mislead someone you have to anticipate how they'll react to your story, you have to make the story plausible enough that they'll believe it, and most importantly, you have to know the difference between when to be frank and when to B.S.
lying brainThere are different categories of lies, such as bluffing or omitting the truth, and each requires its own unique patchwork of brain activity to pull the wool over someone's eyes. One brain region, however, remains consistently active during nearly all forms of lying. The anterior prefrontal cortex, the frontal extremity of the brain directly above the eyes, seems to be the brain's command center for lying. Despite its unfailing activation during lies, until recently it was unclear if this region was busy suppressing the truth or if it served as a moral conflict monitor in the brain that lit up during deception. Basically, if this brain region were missing, would we lie less because we were no longer able to conceal the truth, or more because we no longer found it immoral?

As it turns out, it's possible to find out what our brain would be like if part of it were missing. A group of researchers in Germany's University of Tuebingen recently tested the function of the anterior prefrontal cortex by temporarily disabling it using a method known as transcranial direct current stimulation (tDCS). tDCS works by sending a weak electrical current through the scalp to interfere with the activity of the brain cells below. The effects are harmless and are used to moderately alter behavior and even as a treatment for depression.

To test the relationship between lying and the anterior prefrontal cortex, the researchers wanted to create a realistic scenario where subjects could lie or tell the truth at their own discretion. They used a task called the Guilty Knowledge Test, where two subjects participate in a role-playing game and each is given either the role of an innocent person or a thief. The researchers leave the two subjects alone for several minutes and the thief is instructed to steal money from a room while the innocent person waits outside, and then both subjects are interrogated. To motivate the thief, he gets to keep the money if he can convince the researchers of his innocence. In fact, the innocent person is a collaborator and the subject is always assigned the role of thief.

Just before the interrogation began, the subjects underwent either tDCS of the anterior prefrontal cortex or a sham operation where they sat in the machine but no current passed through it. The subjects who underwent tDCS not only lied more frequently, but their lies were more convincing and they reported feeling less guilty about it afterwards. The thieves got to keep the money. The anterior prefrontal cortex seemed to serve the role of a moral compass, and without it people were able to lie more easily and with fewer qualms.

Exploration of the brain has helped elucidate one of human's oldest tricks, lying, and has even taught us how to improve upon it. When I told my friends about this possibility, they lightheartedly considered calling in sick to work the next day. I am not advocating that we abandon truthfulness, for it clearly has great value. I simply suggest that if someone goes to the trouble of baking your favorite dessert and, although you're touched by the gesture, you cannot feign pleasure, perhaps you should consider becoming a better liar.

Joshua Gowin, Ph.D., earned his doctorate in behavioral neuroscience at the University of Texas Health Science Center in Houston.

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