A long time before the polygraph test was invented, humans found other ways to detect a lie. Back in the Middle Ages, in ancient India and China, authorities asked their suspect to chew a grain of rice (or different substances), and based on the ease of the way they spat and the viscosity of the saliva, the suspect was found guilty or not. For example, in China, a dry grain of rice would be indicative of the dry mouth of a liar. In India, rice stuck to the mouth would be a sign of guilt. Even though these methods were incorrect, they were still fixed on the physiological signs—signs that simply show the way a living organism and a bodily part function.
Over the years, many psychologists have studied how the human body reacts to guilt and lies. Starting in 1914 with Vittorio Benussi, an Italian psychologist, and his published findings on the respiratory symptoms of the lie, we get to Dr. James Mackenzie, a simple cardiologist who also decided to be the first to develop the ink-writing polygraph to track irregular heartbeats, and finally, we get to meet John A. Larson, a young policeman and psychiatrist who dedicated his life to creating something that could detect deceptive behavior accurately by measuring continuous changes in blood pressure, heart rate, and respiration rate.
Even though Leonard Keeler was named “Father of the Modern Polygraph,” his technology couldn’t have been possible without Larson’s early invention. The policeman even solved murders, robberies, thefts, and sex crimes with his creation.
Starting in the 1970s, many psychologists didn’t agree with the way the polygraph worked, especially with his results. Therefore, in 1988, in the SUA, “The Employee Polygraph Protection Act” appeared, forbidding private employers from using the lie detector test during the course of employment, but these days, polygraph tests are allowed only in the investigation of criminal acts or in the hiring process for specific positions that have access to sensitive information.
So how does the polygraph work? The machine measures the activity of the autonomic nervous system through the sensors that are attached to different body parts of the suspect: the stomach, the fingers, and the chest. Besides showing changes in blood pressure and heart rate, it can also measure the electrical activity of the brain. The test doesn’t detect the lie, but the physiological changes that are controlled by strong emotions like fear, anger, and especially guilt.
So the big question is: Can you fool a polygraph test?
The answer is yes. The test can’t be taken as valid proof to declare if someone is truly guilty or not, but people are still obsessed with the methods scientists found to be good enough to cheat the test. Well, there are two possibilities: a physical one or a cerebral one.
The physical one is based on self-inflicted pain: biting your tongue, hiding a pioneer in your shoe, or even contracting and relaxing your muscles. The cerebral one is easier to approach because it includes simple options: you can fool the test by either counting down or by having erotic thoughts and fantasies.
Therefore, the polygraph is a great invention in the psychology world, but we must understand that it is the type of machine that can be used in the correct way as well as in the wrong way.
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