PolygraphElephants can't swim. How can you know if I'm telling the truth? You can tell by testing me with a polygraph machine. Ever since civilization began, people have wanted a way to distinguish fact from fiction. In the Middle Ages, Europeans used torture because they thought that if you stressed and hurt your body enough, the person lying might tell the truth. What this method has in common with today's lie detector, or polygraph, is that there is an involuntary physical response from a person when they are lying. The polygraph has a story of its own, but you will have to decide for yourself whether it is true or not. That story includes: how it was made, how it is used, and whether or not it works. The polygraph machine is made up of three main parts, all made by different people. The first scientific instrument used to measure physiological responses to lying dates back to 1895, when the Italian psychiatrist and criminologist Cesare Lombromso modified pre-existing equipment to measure the physiological changes that occurred in the blood pressure and heart rate of a crime suspect during a police operation. interrogation. In 1921, a Canadian psychologist, John Larson, developed what many people consider the original lie detector, using both respiratory rate and blood pressure. He called this device the polygraph. Several years later, in 1938, Leonard Keeler added the third physiological measurement component of the lie detector, creating the polygraph we know today. This latter device is called a psychogalvanometer and measures changes in the amount of galvanic activity, or sweat, of a person. Once completed, the polygraph machine had many uses. The polygraph test consists of many steps and also includes a pre-test. Before taking a polygraph test, the examiner asks the candidate several control questions to understand how the candidate responds to the questions and to help detect whether he or she is lying during the actual polygraph test. This is important because the examiner will later analyze the test to decide whether the candidate was lying or not. Often questions are used that would have special meaning to the criminal but not to others. During a test usually only 3 out of 10 questions are relevant. The other questions are known as controls. Setting up a polygraph requires several parts. To record changes in blood pressure and heart rate, a cuff is placed on the upper arm.