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Illuminating lies with brain scan outshines polygraph test

It has been demonstrated that when someone is lying, areas of the brain linked to decision-making are activated, which lights up on an fMRI scan for experts to see. While laboratory studies showed fMRI’s ability to detect deception with up to 90 percent accuracy, estimates of polygraphs’ accuracy ranged wildly, between chance and 100 percent, depending on the study. The Penn study was the first to compare the two modalities in the same individuals in a blinded and prospective fashion. The approach adds scientific data to the long-standing debate about this technology and builds the case for more studies investigating its potential real-life applications, such as evidence in the criminal legal proceedings.

Researchers from Penn’s departments of Psychiatry and Biostatistics and Epidemiology found that neuroscience experts without prior experience in lie detection, using fMRI data, were 24 percent more likely to detect deception than professional polygraph examiners reviewing polygraph recordings. In both fMRI and polygraph, participants took a standardized “concealed information” test.

Polygraph, the only physiological lie detector in worldwide use since it was introduced in its present form more than 50 years ago, monitors individuals’ electrical skin conductivity, heart rate, and respiration during a series of questions. Polygraph is based on the assumption that incidents of lying are marked by upward or downward spikes in these measurements. Despite having been deemed inadmissible as legal evidence in most jurisdictions in the United States or for pre-employment screening in the private sector for almost 30 years, polygraph is widely used for government background checks and security clearances.

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