The main idea of a lie detector is that our body can betray us. More specifically, when we lie, the body undergoes certain physiological changes, sometimes manifested in the form of wet palms, excessive sweating, nervous movements, or visually observable tics. Even if you do not detect external signs, the body reacts physiologically through surges in blood pressure, respiratory activity and electrical conductivity of the skin.
Most lie detectors, technically called polygraphic machines, consist of four to six sensors attached to the skin to monitor for these key signs. The process is quite simple - the examiner, after connecting the sensors to your skin, starts asking you a series of questions. Initially, the examiner will ask you the so-called. "Test questions" that will help establish a baseline activity rate and signs specific to each person.
When the examiner asks specific questions, polygraphs can measure your answers and compare them with your data corresponding to "lies" and "truth". Therefore, it is very difficult to fool a lie detector, because even if your appearance and tone of voice may not betray you, it is difficult to keep your body from its natural stress response.
Is there a way to fool the lie detector after all?
There is quite a lot of controversy regarding the use of lie detectors for criminal investigations, as there are many loopholes in the development of a polygraph test that allows you to deceive a device. Given that "truth" is measured based on your "control" responses, it logically follows that you can falsely generate physiological stress responses by telling the truth to a question like "Are you a man?" To do this, it is enough either to strongly strain one of the leg muscles, or to bite your tongue or grab your fingernails into the palm - your body will give a strong physiological response, which is registered as an "anomaly" in the control question. If at the same time you remain calm and indifferent with a dishonest answer, the readings of the polygraph could go astray even more.
Even imagining a frightening image or idea can cause physiological stress in the body, which can also be used to distort sensor readings and confuse measurements when real questions are asked. There are some minor variations on this topic, including philosophical syllogisms, to confuse the detector.
Of course, experts are also familiar with these methods of deception, and they have developed various countermeasures, including the use of the latest advanced polygraph models, which also use MRI scans of the brain to identify active areas for correct and incorrect answers.
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And while lie detectors are still used for a wide variety of purposes, the test results on them are not considered the definitive form of proof of deceit or honesty at this time, as they were in the past.
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