A Polygraph test is commonly known as Lie Detector. Scientists have developed methodology to identify cheating, fraud, trickery and finding truth, which is Lie detection or polygraph testing. Polygraph tool evaluates several physiological procedures and the reactions that one goes through in those processes. Mainly Lie Detector testing is used for crime detection and Employee screening.
Brief History of Lie Detector
In the year 1902 inadequate lie detector test was invented by James McKenzie. In 1921 John Larson invented modern polygraph instrument which gives recorded information on a smoke paper. In 1925 Leonard Keeler further developed instrument with ink pens instead of smoke paper to get better results. Finally in 1992 machine was computerized to record results accurately.
Lie Detection with Polygraph Testing
Lie detection took on scientific aspects with the development of techniques that use measures of physiological responses as indicators of deception. The physiological measurements include heart rate, blood pressure, body movements and electrical conductance in skin. The polygraph instrument contains sensors to measure the physiological phenomena. In polygraph instrument depth of respiration and heart rate are measured by pneumographs chest wrapped, skin conductivity is measured through electrodes attached to finger tips and a blood pressure BP cuff attached on upper arm. While conducting examinations sensors transmit the data to the instrument and print that data on Polygraph Chart. (more…)