Do Lie Detector Tests Really Work?

At one point in everyone’s life, they have told a lie. Despite the nature of the lie and the intention of the lie, it is still a lie. Trying to figure out whether or not someone is lying was a pretty hard task to complete, once upon a time. That was up until lie detector tests (polygraphs) were invented. Lie detector tests gauge whether or not someone is lying based on their vitals, like heart rate, etc. As a matter of fact, I took a lie detector test that made me wonder how lie detectors work.

In the American Scientist, the reader is informed that polygraphs are used widely by the government and big businesses as an extremely powerful tool of social control and surveillance. In addition, the legal system has picked up on the use of polygraphs. The police routinely use polygraphs to navigate their way through interviews and to secure confessions. The only problem with this polygraph is that it is a machine, and all machines are subject to fault, and lie detectors are not excused from this.

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This begs the question: “How accurate are lie detector tests?”

The History of the Lie Detector

In the book by Ken Alder, The Lie Detectors, which talks in-depth about the history of the polygraph. Alder begins the narrative on lie detectors in the 1920s, the era well-known for its psychological inventions including the I.Q. test, and scientific industrial management. In Berkeley, California, the local chief of police, August Vollmer was known as someone who kept up to date with the new advances in science.

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Vollmer had a clear appetence for any new methods in the making to determine deception. Naturally, when rookie cop, John Larson invented the “cardio-pneumo-psychograph”, Vollmer took an interest. John Larson based his invention off of William Marston, a Harvard psychologist who did experiments to determine whether changes in systolic blood pressure was correlated to people telling lies. After a bit of initial doubt, Vollmer was intrigued by the idea and got the teenage son of one of his friends, Leonarde Keeler intrigued as well. According to Vollmer’s plan, Leonarde Keeler would fix what needed to be fixed mechanically to maximize the device’s potential. Meanwhile, John Larson would do what needed to be done to ensure that the device did what it was invented to do. Upon receiving Vollmer’s blessing, Larson took the lie detector to the capital of crime, Al Capone’s Chicago, where he was followed by Keeler. Soon after this, however, their roads parted. With the contributions of these men, we now know of the modern-day lie detector that was “conceived in the psychology laboratory and baptized at the police station.”

Understanding How They Work

The lie detector first began as a simple response that determined changes in systolic blood pressure. Since the 1920s, big strides have been made to better the results and accuracy of lie detector tests. On the website of the American Psychological Association (APA), there is an article on the Truth About Lie Detectors. According to the article, as of recently, the item that is generally used to run lie detector tests assess the three indicators of autonomic arousal. Respiration is one of these indicators. The rate and depth of respiration are assessed by pneumographs that surround the subject’s chest. Another indicator of autonomic arousal is cardiovascular activity. This includes heart rate and blood pressure. These two are evaluated by a blood pressure cuff. The last indicator of autonomic arousal is skin conductivity. Skin conductivity is the phenomenon that skin is momentarily a better conductor of stimuli when events that are physiologically arousing occur. This is measured through electrodes attached to the fingertips of the subject.

Once the examination is underway, the investigator will ask the subject a series of pretest questions. During this phase, the technique that will be used to conduct the lie detector test is explained. Furthermore, it ensures subjects being tested on understanding the questions. This stage also does its job in inducing a subject’s concern about being deceptive. Next, a procedure called a stimulation test will occur. This will demonstrate to the subject the accuracy of the instrument in detecting deception. These are the steps that occur prior to the real test, and once they are complete the real test may begin.

Testing Methods

While there are many questioning techniques used to conduct polygraphs, the most commonly used is the Control Question Test (CQT). This method is mostly used on subjects in criminal investigations. In the Control Question Test method, investigators ask control questions, and relevant questions in order to compare the responses. For example, in a murder investigation, the investigator would ask a relevant question, like “Did you shoot your wife?” Then, a control question will be asked by the investigator, like “Have you betrayed anyone who trusted you?” These control questions serve the purpose of controlling the generally threatening nature of relevant questions.

Due to the fact that control questions are designed to arouse one’s concern about their past truthfulness, and relevant questions serve the mere purpose of asking about a specific crime that they did not commit, a person telling the truth would end up fearing control question more than they would fear relevant questions. Based on this, a pattern of greater physiological response to the control questions would point to the fact that the subject is being truthful. In contrast, a pattern of greater physiological response to the relevant questions would point to deception.

Another method of polygraph testing is the Guilty Knowledge Test (GKT). In this test, multiple-choice questions are posed to the subject in question that only a guilty subject would know. A larger physiological response would point to deception

What’s Wrong With Polygraphs?

While it seems that these polygraphs are an amazing idea, there are issues with them that put their accuracy in question. The biggest problem is that there is no real evidence that any pattern of physiological reactions is unique to deception. On Britannica’s website, there is an online article titled “Do Lie Detectors Actually Work?” According to this article, for whatever weird reason, an honest person can be nervous while answering a question truthfully. In the same sense, a dishonest person may not be nervous as they deceptively answer a question. So although the lie detector test does it’s job in measuring physiological factors associated with being nervous, that does not at all mean that the machine is always effectively able to distinguish whether a person is telling the truth or whether that person is lying.

Another topic questioning the validity of lie detector tests involves the placebo effect. The placebo effect is the belief held by the subject being tested that the item to be used will work exactly as it is meant to work. There is no separation between these placebo-like effects and the actual relationship between deception and their physiological responses. Polygraph tests look more accurate than they might actually be because people who believe that the polygraph will work get very nervous before telling lies. If this true, rather than being lie detectors, the machines then become fear detectors.

The last big issue that questions the accuracy of the lie detector test is that there are clear strategies that can be used to “beat” lie detector tests. In order to fool this machine, there are a series of things that can be done. As stated before, you can relax before telling a lie in order to stop your body’s physiological reactions. In addition to this, simple physical movements can enable the subject to fool the lie detector test. You can also use psychological interventions, like manipulating how the subject feels about lie detector tests. Lastly, pharmacological agents can be used to alter the arousal patterns of a person.


I-Search essays are different from your normal essay. When writing an I-Search essay, the author must do deep, deep research in order to have a good understanding of the questions they ask, and what the answer to that question is. Once you have your notes on the topic done, you begin to make an outline and determine where each piece of information will fall. Only then can you begin to write a rough draft of your essay; then you need to perfect it until you have a final draft. Using these steps I was able to learn more about polygraphs and their history, use, and faults. Based on the information, I can conclude that polygraph tests are not as effective as some perceive them to be.

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Do Lie Detector Tests Really Work?. (2020, Sep 27). Retrieved from

Do Lie Detector Tests Really Work?

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