MadSci Network: Neuroscience |
Dear Senthil, What is commonly called « lie detector » is actually a polygraph that essentially measures four parameters : heart rate, blood pressure, respiration, and sweating (see the image at the bottom). The variation of these parameters may be associated with some emotions but the question is highly controversial. To my opinion, what should be clear is that the polygraph measures the parameters mentioned above but not in any way whether a person is telling the truth or not. Moreover, the output from a polygraph may fail to detect real emotions (ex. fear) behind lying. Indeed, a 1983 report by the Office of Technology Assessment concluded that polygraphs are not an effective scientific method to check for security breaches. I also think that having “false positive” is very dangerous: a person may tell the truth while being highly stressed by the situation. According to Alan P. Zelicoff (physicist at the Center for National Security and Arms Control at Sandia National Laboratories in Albuquerque, New Mexico): there are “tremendous cynicism and doubt about the utility of the test in both management and technical staff.” To answer your question more precisely, there are no study that have used PET or fMRI as a “lie detector”. On the other hand, some people think that it would yield better results than the polygraph because there are growing evidence that certain parts of the brain are involved with emotions (discussed briefly in Holden, 2001). On the other hand, one must remember that emotions does not necessarily mean truth or lie although it may be indicative in some cases. Thanks for the interesting question! Eric See also: Holden C. (2001) Polygraph screening. Panel seeks truth in lie detector debate. Science 291(5506):967. Lykken DT. (1991) Why (some) Americans believe in the lie detector while others believe in the guilty knowledge test. Integr Physiol Behav Sci 26(3):214-22.
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