Once a thief always a thief. Could this proverb be true from a neuroscientific perspective? According to a team of researchers in the Experimental Psychology Department at University College London, a neuronal mechanism could be the cause for the progressive learning of dishonesty. Their study shows that, through a snowball effect, small acts of cheating could result in more significant acts of dishonesty. How does our brain learn to be dishonest?

Starting from the observation that many fraudulent acts begin as minor transgressions, Neil Garrett and colleagues attempted to empirically demonstrate this phenomenon of escalating dishonesty and explore the underlying neurological mechanisms. They combined brain imaging with a behavioral task in which participants were repeatedly given the possibility to act dishonestly.

The scientists developed two protocols in which one person had to advise another in estimating a sum of money, knowing that in some cases, lying could be profitable...

Thus, in the first experiment, the researchers told 55 participants (34 women, 21 men, average age = 23.02) the following: you will be placed in a booth and given 30 seconds to analyze an image of a clear jar containing a quantity of coins; you will then have four seconds to indicate to an estimator located in another booth (but who doesn't actually exist) the amount of money that you think is in the jar; you are thus their "advisor." The participants were also told that the estimator would see a smaller image of the jar for only one second and, after receiving their advice, would propose an estimate on behalf of the two. In the end, a trial would be chosen at random to be given the potential reward. From this experimental basis, several reward scenarios were disclosed to the participant-advisor; some of them encouraged the advisor to lie in order to earn more money, sometimes at the expense of the estimator. For example, participant-advisors were informed that the more the estimator overestimated the amount in the jar, the greater the reward for the advisor. A second experiment, designed to extend and reproduce the results of the first one, was also carried out with 25 participants (18 women, 7 men, average age = 20.76).

Neil Garrett’s team observed that dishonesty grew in proportion to the potential gains. Indeed, the instances of deliberately erroneous advice, which was initially very low, increased as the experimental sessions progressed. This escalation was observed when the lies were likely to profit the participant-advisor, but not the estimator (the authors call this “selfish dishonesty”). Using a functional MRI, the neuroscientists observed a brain area in participants, the amygdala, became progressively less active. The area is one of the brain’s centers for processing emotions.

The hypothesis goes as follows: at first, out of fear of punishment, an act of dishonesty activates the amygdala. But if no punishment ensues, fear diminishes until it disappears… a true desensitization process occurs: as unpunished cheating multiplies, the brain no longer receives an alarm signal. According to the study, measuring the reduced sensitivity of the amygdala to dishonesty could allow us to predict the extent of the next selfish trickery.

The conclusion of this research is thus rather unsettling: according to the authors, a brain mechanism, under "favorable" conditions, could encourage dishonesty!