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In 1902 an inadequate lie detector test was invented by a man named James McKenzie. Later on in the 18th century, 1921, a medical student named John Larson from the University of California invented the modern polygraph instrument, which was much more accurate in its results than the previous machine. Although it recorded several different physiological responses, it was not as advanced as the modern polygraph instrument; it measured the subjects pulse rate, blood pressure and respiratory rate and recorded the information on a rotating drum of smoke paper. In 1925 Leonarde Keeler refined the instrument invented by John Larson; instead of using smoke paper to record changes in the suspects’ reactions, he incorporated ink pens in order to ensure the efficiency of the machine. In 1938 the machine was further improved by Keeler. He added another measuring component, galvanic skin resistance. The polygraph machine continued to advance throughout the years; a man named John Reid introduced the idea of using ‘control questions’ as a means of comparison. After many years of experimenting with ways to improve the machine, the machine was finally computerized in 1992, this allowed the machine to record the results of the test more efficiently.