Lie detector has been in news recently as Rajesh Talwar, accused in the Noida twin murder case involving his 14 year old daughter Aarushi was subjected to polygraph test by the CBI. Polygraph (or lie detector) is an instrument that measures physiological changes [in the parameters like blood pressure, pulse, respiration and skin conductivity] caused by the sympathetic nervous system during a conversation.

But there exists a controversy on reliability of this device/ technique. William G. Iacono, Professor of Psychology and Neuroscience at McKnight University and Director, Clinical Science and Psychopathology Research Training Program at the University of Minnesota, published a paper titled “Forensic Lie Detection" in 2001 which concludes that "it does not pass muster as a scientifically credible test".

Apart from polygraph, there are other methods also for lie detection such as voice stress analysis, functional magnetic resonance imaging (fMRI), Brain fingerprinting (using electroencephalography), truth drugs such as sodium thiopental (Remember: Kamal haasan's movie - "Kuruthippunal"), Cognitive chronometry (Timed Antagonistic Response Alethiometer - TARA), functional transcranial Doppler (fTCD) etc.

Even there is a scene in Rajinikanth's movie "Baba" where he detect lie from the eyes of the speaker. Even lie can be detected at some point; but truth can never be identified as simple as that.


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