Polygraph instruments, also known as lie detectors, have long been a topic of fascination and controversy. Often featured in popular culture, these devices have garnered a certain mystique over the years. However, many myths and misconceptions about polygraphs continue to circulate, leading to misunderstandings about their function, accuracy, and application. In this article, we aim to debunk common myths and set the record straight regarding polygraph instruments.

Myth 1: Polygraphs Directly Detect Lies

Fact: Polygraphs measure physiological responses, not lies. The polygraph instrument records a subject’s physiological changes, such as heart rate, blood pressure, respiratory rate, and skin conductivity. These changes may indicate stress or anxiety, which are often associated with deception. However, it is important to understand that polygraphs do not directly detect lies; they only measure physiological reactions that can be correlated with deceptive behavior.

Myth 2: Polygraph Results are Infallible

Fact: While polygraphs can be a useful tool, they are not infallible. The accuracy of polygraph tests varies depending on several factors, including the examiner’s skill, the subject’s emotional state, and the specific test format used. Research indicates that polygraph accuracy rates range from 70% to 90%. This means that false positives (identifying truthful people as deceptive) and false negatives (failing to identify deceptive people) can occur.

Myth 3: All Polygraph Examiners are Equally Qualified

Fact: Polygraph examiners vary in skill and experience. A well-trained and experienced examiner is crucial to obtaining accurate results. It is essential to ensure that the examiner administering the test is certified by a reputable organization, such as the American Polygraph Association (APA) or a similar body in the examiner’s country.

Myth 4: You Can “Beat” a Polygraph Test by Remaining Calm or Using Countermeasures

Fact: While it is true that some individuals may attempt to manipulate the results of a polygraph test by employing countermeasures or remaining calm, skilled examiners are trained to detect these tactics. Examiners may use a variety of methods, such as control questions and other techniques, to account for these countermeasures and increase the test’s accuracy.

Myth 5: Polygraph Tests are Admissible in Court

Fact: In many jurisdictions, polygraph results are not admissible in court due to concerns about their accuracy and potential for bias. However, polygraphs can still be used during criminal investigations, pre-employment screenings, and other situations where assessing credibility is important.

Myth 6: Polygraph Tests are Only Used for Criminal Suspects

Fact: Polygraphs are used in various contexts, including pre-employment screenings, security clearance evaluations, and relationship counseling. In some cases, individuals may even volunteer to take a polygraph test to clear their name or prove their honesty.

Myth 7: Polygraph Tests are Invasive and Uncomfortable

Fact: Modern polygraph tests are minimally invasive and generally well-tolerated by subjects. While the subject may be connected to various sensors during the test, the process is usually painless and non-intrusive.

Myth 8: A Single Question Determines the Outcome of a Polygraph Test

Fact: Polygraph tests typically involve a series of questions designed to gauge the subject’s overall truthfulness. The examiner will often include relevant and irrelevant questions, along with control questions, to establish a baseline and monitor the subject’s physiological responses throughout the test.

Myth 9: Taking Medication or Consuming Alcohol Can Affect Polygraph Results

Fact: Some substances, such as alcohol or sedatives

, can potentially affect polygraph results by altering a subject’s physiological responses. However, experienced examiners are trained to recognize when a subject may be under the influence of a substance and can either account for it during the test or postpone the examination until the effects have worn off. It is essential for subjects to be honest with the examiner about any medications or substances they have consumed prior to the test.

Myth 10: Polygraph Tests are Lengthy and Time-Consuming

Fact: While the length of a polygraph test can vary depending on the complexity of the case and the number of questions asked, most tests typically last between one and three hours. This includes the pre-test interview, the actual testing phase, and the post-test analysis. Although this may seem lengthy, it is essential to allow adequate time for the examiner to gather accurate information and assess the subject’s truthfulness effectively.


Understanding the realities of polygraph instruments is essential in making informed decisions about their use and interpretation. While polygraph tests can be a valuable tool in certain situations, it is crucial to recognize their limitations and rely on the expertise of qualified examiners. By debunking common myths surrounding polygraph instruments, we can better appreciate their role in assessing credibility and detecting deception.