Do Lie Detectors Really Work?


For as long as humans have been deceiving one another, people have tried to develop techniques for detecting lies. Lie detection took on scientific aspects in the 20th century with the development of techniques that use physiological responses as indicators of deception. The most well-known of these is the polygraph test.

What is a lie detector?

Lie detectors are devices that monitor the involuntary physiological changes in a subject’s body during a questioning session by a trained examiner. Those changes include heart rate, blood pressure, and galvanic skin response (a proxy for perspiration). The theory is that when people are lying, their responses to questions will be different from those of people who are telling the truth.

During the first decade of the 20th century, American researchers and police officers developed various devices that monitored a subject’s cardiovascular, respiratory, and skin conductivity responses as they answered a series of pre-test control questions and “relevant” questions related to an investigation. They called the results a polygraph test, or lie detector test.

More recent research has focused on using fMRI to decode mental content, and researchers have been able to detect specific patterns of neural activity that occur during a lie. However, it is still possible for subjects to manipulate the resulting data by using mental countermeasures such as eye blinking or suppressing emotional responses.

How does a lie detector work?

Lie detectors (polygraphs) are devices for recording physiological phenomena such as blood pressure, heart rate, and perspiration—reactions allegedly linked to lying—as the subject answers questions from a trained examiner. These data are then analyzed and used to make a determination as to whether or not the subject is lying.

Physiological changes can be caused by a number of things, and there is no evidence that deception causes a unique set of reactions. Furthermore, people can use countermeasures to skew the results of a polygraph test. Examples include taking sedatives, applying antiperspirant, and holding their breath to reduce sweating.

Despite the popularity of polygraph tests, many psychologists believe that they can’t accurately detect lies. This is because the polygraph can’t distinguish between psychological and physiological changes that often accompany dishonesty from the placebo-like effects of undergoing questioning. Additionally, studies have shown that experts are no better than lay persons at determining when a person is lying (Vrij 2000). As a result, many experts agree that the use of polygraphs is unsupported by science and should be discontinued. Get more info on this Lie Detector Test website.

Can a lie detector be fooled?

A lie detector is a machine that claims to be able to tell when someone is telling the truth. It measures a subject’s physiological responses, such as spikes in heart and breathing rates and increased perspiration, which are all said to be caused by lying. Newer technology, such as the one developed by Jim O’Shea and colleagues at MIT, uses 40 different physical channels to measure the subject’s movements, looking for specific patterns that indicate deception.

But while these tests are incredibly expensive and require a trained examiner to operate, it’s not hard to fool a lie detector. For example, serial killer Gary Ridgway was able to pass multiple polygraph tests by taking sedatives and using antiperspirant. More subtle tricks include forcing yourself to smile, biting your tongue, or even inflicting pain on yourself to skew results. These methods aren’t foolproof, but they do reduce the accuracy of the test by 20%. That’s why so many people oppose the use of lie detectors, especially in high-profile cases like the Senate confirmation hearings for Supreme Court nominee Brett Kavanaugh.

What are the best lie detectors?

The polygraph is still the world’s best-known deception detector, even if it’s been plagued by accusations of questionable accuracy. It dominates the public perception of lie detection and remains a $2 billion industry. In the era of fake news and falsehoods, dubious new techniques could easily slip neatly into the role that the polygraph once held, warns one expert.

The problem is that polygraphs, like any other lie-detection technique, can only measure indirect effects of lying. People who are attempting to fool the test may have a variety of physiological responses, from sweating on the palms to changes in eye dilation. They may also have strategies to help them ‘beat the machine’ by changing their own answers, varying their breathing and body language.

For all these reasons, the best lie detectors should rely on proven scientific methods to achieve the highest levels of accuracy. In a world where people’s lives and freedom depend on the truth, we can’t afford to settle for anything less.