Poor Pinocchio, he never had a chance. A new study in Nature Neuroscience confirms the reason for the puppet's ever-growing proboscis: The more we practice prevarication, the easier it gets.

In the latest contribution to research literature on lying, scientists at University College London and Duke University have shown that repetition of small lies weakens the negative emotions associated with telling untruths, leading to bigger lies down the road.

In a laboratory experiment, 80 college volunteers told a second participant their best guess at the number of pennies in a jar. Various scenarios gave them incentives for being dishonest about the amount. In one, dishonesty about the amount benefited the first subject only. In others, dishonesty benefited both or benefited the first subject but hurt the second participant.

“People often perceive self-serving dishonesty as morally wrong and report uneasiness when engaging in such behavior,” the authors wrote. “Consistent with these reports … measures of emotional arousal are observed when people deceive.”

The researchers scanned subjects’ brains with an fMRI while they performed the various tasks. Focusing their attention on the amygdala, where emotions, emotional behavior and motivation are all integrated, the scientists discovered that the more times subjects lied to benefit only themselves, the less activity in the amygdala. In other words, more lying appeared to lead to fewer qualms about lying.

On one level, the finding wasn’t all that surprising. Neuroscientists have shown over the years that repeating a stimulus that evokes a negative emotion diminishes the intensity of that emotional response: for example, soldiers becoming inured to the horrors of battle.

What may be more surprising is what other researchers have discovered about honesty.

Last year, scientists at Jerusalem College of Technology in Israel conducted an experiment similar to the one above. Instead of a brain scanner, however, the researchers asked participants an extensive series of questions to determine their backgrounds, personalities, education, employment, even IQ. Only one relationship emerged: The more honest someone was, the higher his or her intelligence.

The question of whether these “smarter” people were really more moral went unsettled. Perhaps those who were more intelligent saw through the experiment, realized it was a setup, and chose to answer honestly because of concerns about self-image. Or perhaps the smarter a person is, the better able they are to assess the potential negative consequences of lying, even with a short-term gain.

A central question at the core of these experiments is one that has engaged moral philosophers for millennia: Are human beings predisposed to tell the truth? There are two competing theories about the nature of honesty. The “Grace” theory holds that truth-telling is innate and arises from a lack of temptation. The “Will” theory, on the other hand, holds that truth-telling depends on a person's ability to resist temptation.

To discover at what point people will choose to be dishonest, despite harm to their self-interest or self-image, researchers at Virginia Tech looked at people who had damage to the dorsolateral prefrontal cortex, a highly-evolved structure at the front of the brain involved in working memory, planning and cognitive control, including moral decision-making.

In a paper published in Nature Neuroscience two years ago, the scientists posed the question: Was the dorsolateral prefrontal cortex the brain switch that controlled the cost/benefit analysis of honesty versus dishonesty? Previous experiments had detected activity in the dorsolateral prefrontal cortex in lying experiments, but it wasn't clear whether the activity signaled lying per se or discomfort because of a desire to tell the truth. Some of the participants in the Virginia Tech study had suffered damage to their dorsolateral prefrontal cortex, and it was these subjects, the scientists found, who were less averse to lying and also less concerned about their self-image. With the source of cognitive control removed, the brain is more likely to “choose” to lie.

Count one for the “Will” theory. Which means, perhaps, that Russian author Dostoevsky was right: “Nothing in this world is harder than speaking the truth.  . . . ”

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