Info about Lie Detectors
How lie detectors work
Everybody lies. This is a fact that cannot be denied. However, what makes the difference is the importance of the lies we tell and sometimes, how often we tell them. Of course, a white lie will do no harm, but sometimes, by lying all the time we end up lying ourselves. As a consequence, the idea of a device that is able to say when a person lie is quite compelling.
Nevertheless, a lie detector cannot tell if a person lies or not. What a lie detector can do is to measure the intensity of the person’s in cause physiological response to a question asked.
A lie detector, also called polygraph is a device that monitors your vital signs and the changes they suffer during an interview. The examiner has the duty to study these chances and decide if the verbal response is true or false. What a polygraph machine monitors are the blood pressure, heart rate, respiratory tare and the electro-dermal activity. When these signs vary significantly, the person interrogated may be lying.
The way the polygraphs get all the data about the person being interviewed is through some tubes and wires that are placed strategically around the body. The respiratory rate is monitored by two tubes that are put around the chest and abdomen. When changes in the muscles controlling breath are made, the data are transmitted to a computer. So does the cuff that I wrapped around the arm to monitor the blood pressure and heart rate. The electro-dermal activity or the galvanic skin resistance is measured by the amount of sweat on the fingertips.
All these reactions are produced when somebody is under stress and lying can be a very stressful activity. When we lie, our blood pressure and heart rate increase, we breathe faster and we seat more. Some lie detectors have supplementary components that measure the movement of the legs and hands. When you are nervous, you tend to have some reflex responses.
Why a polygraph cannot be trusted completely is because all these reactions can be triggered by other factors than lying. You can be nervous from a different cause or you can just display other emotion such as excitement. A lie detector cannot tell if you lie or if you just happen to live another stimulus that makes your body react.
What is more, a polygraph cannot say what you are lying about. Maybe your response is a lie, but that does not mean that the actual answer is completely opposed to what you are saying. A detail that you do not want to tell about may make you a liar on the eyes of others. In addition, a lie detector can be tricked by using different drugs that make you relax and lying will not be so obvious.
Lie detectors are not linked only to criminal investigations. You may be surprised to be asked to take a lie detector test when you apply for a job. Polygraphs are now used by both state institutions and private companies when it comes to hiring interviews.