Brain scans detect lies better than polygraph tests, new study shows

Forget fact checkers or polygraph tests. A functional magnetic resonance imaging (fMRI) brain scan might be the best way to tell if someone is lying.

According to a study from the University of Pennsylvania, our brains are more likely to give us away when we’re lying than sweaty palms, rapid breathing or spikes in blood pressure, the factors tracked by polygraph tests.

The researchers directly compared the ability of two techniques — fMRI and polygraph tests — to detect concealed information. They had 28 participants secretly write down a number between 3 and 8 on a slip of paper. Each participant then had both lie-detection tests, in random order, a few hours apart. During both sessions, they always answered “no” when asked if they had picked a certain number, which meant that one out of the six answers was a lie.

Three fMRI experts and three professional polygraph examiners then independently analyzed the results. The fMRI experts were 24 percent more likely to detect the lie than the polygraph experts, as recently reported in the Journal of Clinical Psychiatry.

Although the study wasn’t designed to evaluate the combined use of both techniques, the polygraph and fMRI results agreed correctly on the concealed number for 17 participants. So they plan to investigate in the future whether these techniques are complementary.

The study includes only a small number of participants, but the research team is encouraged by the results. “While the jury remains out on whether fMRI will ever become a forensic tool, these data certainly justify further investigation of its potential,” said Daniel Langleben, MD, first author and a professor in psychiatry, in a recent news release.

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

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