How to spot a lie: brain scans outperform lie detectors

fMRI wins out in the first comparison of the two technologies.

8th November 2016
How to spot a lie: brain scans outperform lie detectors © iStock

Fibbers watch out: new research at the University of Pennsylvania has shown that brain scans are significantly more likely to spot lies than traditional lie detectors.

It's the first time the two technologies have been compared in a controlled experiment. A polygraph, commonly known as a lie detector, measures physiological activity such as electrical skin conductivity, heart rate and respiration, with the idea being that these will spike when someone is lying. The brain scans, on the other hand, use functional magnetic resonance imaging (fMRI) to monitor brain activity by detecting changes associated with blood flow. Previous studies have shown that when people are lying, areas of the brain linked to decision making 'light up'.

The researchers asked 28 participants to choose a number between three and eight. They were then instructed to answer "no" to questions about all of the numbers, making one of their six answers a lie. The tests were carried out while the participants were either hooked to a polygraph or lying inside an MRI scanner, and the results were compared to find out which technology was most effective at spotting deception.

The brain scans were found to be 24 per cent more accurate at detecting lies than the polygraph. What's more, when the polygraph and fMRI both agreed on the lie, they were 100 per cent correct.

This brings up the controversial question of whether brain scans could be an effective way to catch criminals. "While the jury remains out on whether fMRI will ever become a forensic tool, these data certainly justify further investigation of its potential," says Daniel D. Langleben, lead author of the study.

 


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