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Polygraph Explained

Updated: Oct 19, 2023

Polygraph, commonly known as the lie detector test, has been a popular method for detecting deception for decades. The test measures physiological responses to questioning to determine whether an individual is telling the truth. But how does the polygraph work, and what is its scientific basis? Raymond Nelson, a renowned expert in the field, explains the principles behind polygraph in his article “The Scientific Basis to Polygraph.”


According to Nelson, a polygraph or lie detector test works on the assumption that deceptive individuals experience increased neurological activity when lying. This increased activity leads to changes in physiological responses such as heart rate, blood pressure, respiration, and electrodermal activity (eccrine sweat gland activity). The polygraph machine records these responses while the individual is answering questions, and a trained examiner then analyzes the results to determine if the person is being truthful or deceptive.


The polygraph test involves two types of main questions: control questions, which are used to establish a baseline physiological response, and relevant questions, which are specific to the incident being investigated. The responses to relevant questions are compared to the answers to control questions to determine if the person is lying or telling the truth.


Nelson explains that the validity of the polygraph test is supported by scientific research. Over the years, numerous studies have shown that a lie detector test is highly effective in detecting deception, with accuracy rates ranging from 70-90%. Factors that can influence the results include the individual’s medical history or medication use, the examination quality, and the examiner’s qualifications. Therefore, finding a well-qualified and experienced polygraph examiner is vital to a successful test.


The scientific basis of polygraph lies in its ability to detect changes in physiological responses, typically associated with deceptive behavior. The test has been supported by scientific research, with numerous studies showing its effectiveness in detecting deception.


Understanding the principles behind the polygraph test is crucial for evaluating its reliability and effectiveness. The scientific basis of polygraph provides a solid foundation for its use in various applications, and its accuracy has been proven repeatedly.


Whether you are an individual looking to take a polygraph test or a company considering using it for pre-employment screening, understanding the science behind the test is essential for making informed decisions.


Read Raymond’s article here: CLICK HERE

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