How to Read a Lie Detector Test



Lie detectors (also known as polygraphs) record physiological responses like heart rate, blood pressure and perspiration. These responses are then compared to your answers to relevant and control questions.

But it’s surprisingly easy to game a lie detector test using various countermeasures. Here’s how. The basic idea is to ramp up your physiological responses when answering control questions (like “Is this a safe room?”). This will send your relevant responses off the charts.

Physiological responses

While it is not a sure thing that anyone can beat a lie detector test (some people, like the infamous Soviet spy Aldrich Ames, did), there are certain medical conditions and psychological conditions that can skew results. These include mental illness, drug use, heart disease and being pregnant.

During the test, sensors attached to the subject measure their breathing rate, pulse, blood pressure and perspiration. The examiner then records a graph showing their responses to relevant questions and control questions. A large line on the chart indicates that the person is lying while a smaller one means they are telling the truth.

The examiner looks for peaks in these readings to determine whether you are being deceptive. These peaks are often caused by anxiety or stress. They can also be caused by a combination of these factors as well as other environmental or physical issues. If the peaks are inconsistent with your answers to the relevant and control questions, you will fail the test.

The test’s purpose

Lie detectors measure changes in various aspects of a person’s physiology while answering questions. They use sophisticated equipment to record and analyze these changes in order to determine if a person is lying or telling the truth. Several studies have shown that most liars show similar patterns of physiological responses, which sensitive equipment can detect. During the test, an examiner will ask three or more “control” questions unrelated to the subject’s questioning to establish a baseline for the person’s reactions. This is followed by a series of relevant questions. A person will be deemed to have told the truth if their physiological responses to these questions are higher than their responses to the control questions.Get more info on this Lie Detector Test Price website.

If a person’s test results in a “deception indicated” result, they will be suspected of lying and could lose their job, get arrested, or end up in jail. Alternatively, if their test results in a “deception not indicated” (DNI) result, they will be found to have told the truth.

The examiner’s role

The examiner is responsible for interpreting the results of your polygraph test. He typically starts the session with a pretest interview to determine answers to “control” questions (age, eye color, height) and then asks you a series of relevant and control questions. He monitors your heart rate, blood pressure, and respiratory and perspiration rates during the test. He looks for abnormal changes in the data that could indicate deception.

The assumptions that lying produces physiological responses and that examiners can accurately interpret these signals are what make up the basis of the polygraph’s methodology. However, human errors in interpreting these signals do occur.

Before taking a lie detector test, you may want to practice countermeasures for beating the machine. However, these tactics don’t work very well. Biting your tongue or putting a tack in your shoe won’t affect sweat levels, for example, and imagining telling a lie when asked a question will only confuse the examiner.


Many people believe they can beat a lie detector test. In fact, some of them have succeeded in doing so. This is a big reason why many skeptics think it’s unfair for the test to be used in court.

Some countermeasures involve increasing the person’s physiological response. This can be done by breathing more rapidly, tightening muscles, biting the tongue, performing taxing mental multiplication and other tricks. Others are more subtle. Some people answer questions oddly or vaguely so that the examiner can’t get a read on their response. Other people poke their foot to artificially stress themselves.

The simplest way to reduce false positives is to ensure that the person’s exam environment and testing conditions are appropriate. For example, being hungry or tired can cause a false positive result.