Knowing when someone is lying is a difficult feat. But a polygraph test can help determine whether a person is telling the truth or not.

But how accurate are polygraph tests? What can make them inaccurate? There are a number of factors that can affect the results of a polygraph.


Polygraphs work on the theory that when you lie, your body experiences heightened levels of stress and nervousness. This translates to physical changes such as an increased heart rate and blood pressure. These changes are then detected by the machine and recorded on a chart. This information is interpreted by an examiner who then determines whether you’re lying or telling the truth.

The accuracy of polygraphs has been called into question for as long as they’ve existed. Despite this, they continue to be used as a primary tool in law enforcement and criminal justice systems.

The polygraph has a number of flaws that make it unreliable. For example, some people may be able to fool the polygraph by using certain drugs. Additionally, a person’s physiological responses can be affected by many different factors other than lying. This includes PTSD, alcohol withdrawal, psychosis and general anxiety. These can all cause a false positive test result. Furthermore, a polygraph examiner can also be biased towards certain subjects.


Every body movement – from lifting your leg to nodding your head – requires complex communication between the brain and muscles. Doctors can use electrodiagnostic tests to measure the health of your muscles and nerve cells that control them. This includes EMG and nerve conduction velocity (NCV) tests.

During this test, doctors will attach a recording electrode to your skin over the nerve or group of nerves that you’re having tested. They will then stimulate that nerve by sending a short electrical pulse through the stimulating electrode. You might feel slight discomfort for a few seconds. I recommend this website for more Lie Detector Test.

This type of machine-enhanced lie detector looks at tiny flickers of facial movements and clusters them into patterns that are supposedly linked to lying. However, numerous studies have shown that these systems are no more accurate than random guessing. The results could be affected by many variables, such as your mood and the examiner’s preconceptions about you. Other factors include mental or physical conditions that affect your physiological responses and the types of questions you’re asked.


The EEG is a neuroimaging technique that measures the brain’s electrical activity. It looks for a pattern called P300, which is activated when the subject recognizes information they should not know (like a familiar object or question). It has been shown to have only 40 to 80 percent accuracy, and there are many ways that people can game the test.

Other neuroscience-based techniques promise more sophisticated types of lie detection. For example, fMRI can track the flow of blood to different areas of the brain and can detect differences in synchrony between the two sides of the brain when subjects are asked questions related to lying.

However, these methods require sophisticated equipment and trained examiners to interpret the results. They also raise privacy concerns because of the way that fMRI scans are done and how law enforcement might use them. Just as we have to prove that drugs are safe and effective before they can be used, we should demand the equivalent of premarket approval for these technologies.

Skin Conductivity

In a basic lie detector test, sensors monitor heart rate and galvanic skin response. This data is analyzed by computer software to determine whether the subject is telling the truth or lying. However, this type of test is not always accurate as the results can vary greatly from one person to another. For example, some people can train themselves to control their heart rate and galvanic skin responses, which can cause the machine to misread the data.

In addition, some people can tell a lie consistently without feeling any discomfort, which makes the polygraph ineffective. Furthermore, studies of brain activity show that pathological liars may have a larger volume of white matter in the prefrontal cortex, which makes them more skilled at lying. Despite these limitations, some scientists believe that a future with a reliable way to detect lies is possible. However, that requires further research into how a person’s body responds to different stimuli and the influence of those responses on their behavior.