Wednesday, February 23, 2011

How To Cheat a Brain-Scan-Based Lie Detector

Via Research Digest.
Sure, it's possible to differentiate patterns of truth-telling brain activity from patterns of lying-related activity. But contrary to media hype, experts have been quick to point out that the accuracy of brain-scan based lie detection is often no better than with traditional approaches, such as the polygraph. Furthermore, these experts warn, brain-scan methods could, in theory, be easily thwarted by liars with even modest levels of guile. That claim is no longer purely theoretical, for in a new study, Girgio Ganis and his colleagues have used a popular paradigm to show just how easy it is for lying participants to trick the brain-scanner.
Twenty-six participants had their brains scanned whilst they looked at the same six dates appearing for half a second each, one at a time, on a screen. For each date they had to indicate with a button press whether it was their date of birth - yes or no. This was repeated several times. In the truth-telling condition, none of the dates was their birth date and the participants simply told the truth and said 'no' to each date. In the lying condition, one of the dates was their birth date and their task was to lie and indicate 'no' whenever it appeared. An equivalent set-up in a real-life criminal case might involve a suspect repeatedly looking at the same selection of knives and indicating whether they owned any of them. One further twist to the task was that participants had to look out for a further specific meaningless date - this was just to make sure they stayed engaged with the task.

Click Here to Read: How To Cheat a Brain-Scan-Based Lie Detector

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