Can a Brain Scan Predict a Broken Promise?

A new study suggests that brain activity may give away dishonest intent







The researchers ran a brain-scanning experiment in which pairs of participants played a well-established economic game involving trust. Player A, who was outside the MRI scanner, had to decide whether to keep or give away a certain amount of money -- say, $1 -- to Player B, who lay in the scanner.

If Player A decided to give the money to Player B, the amount would be increased five times (to $5). Once entrusted with the money, Player B could choose to either split it with Player A, so that each ended up with equal shares, or to keep it all.

Before Player A decided whether to hand over the money, player B made one of four promises: That if given the money, he would always, mostly, sometimes or never share it. The twist, however, was that once given the money, Player B could break his promise and keep the entire amount. Player A therefore faced a dilemma: to trust or not to trust the promise.

The main objective of this study was to illuminate how brain activity differs when promises are kept and when they are broken. Therefore, Player B’s brain activity was measured at three points during each game: When he made his promise; while he waited for player A to decide whether to trust him; and finally when he decided whether to keep his promise to share or not.







The study provides an interesting insight into how deception can be investigated experimentally. Lately, research into the brain correlates of deception has been heating up. Most recent studies have investigated deception in the context of lie-detection, and they found increased brain activity in a number of regions, including the anterior cingulate cortex and dorsolateral prefrontal cortex.

However, such findings should be treated with caution, because the participants of most of these studies were instructed to tell a falsehood without having a choice about whether or not to do so. In the Baumgartner et al study, the researchers observed people doing what came naturally to them in a social interaction – and for about half, the experiment was enough to elicit deceptive behavior.

These findings, therefore, bear more relevance to real-life deception than those of most previous studies. They also show that deception can be successfully examined as a social act rather than in the context of lie-detection. This makes it possible to relate the findings to the wider spectrum of social behavior in which trust, cooperation and (unfortunately) deception are intimately linked.



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