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How Is A Lie Detector Test Performed?

The majority of lie detectors are instruments which measure changes in certain parts of the physiology of an individual when they answer questions. The idea is that if someone responds more strongly to certain kinds of questions, the individual can be determined as innocent or guilt-free. If a person’s behavior is not considered innocent or innocent, this is referred to as an inconclusive outcome.

Through the years, laboratory and field research has revealed that the majority of liars exhibit similar patterns of change of physical behaviour that sensors can detect. Of of course, there are instances when some liars fail to display the same physical indicators like the majority. Because of this, lie detectors can have margins of error.

This page will concentrate on two test to detect lies:

(1) EyeDetect(r)

(2) Polygraph

The two devices were proven by field and laboratory research to possess more than 80% accuracy in detect deceit. If a lie detector test system achieves an accuracy of 80% or more and is therefore not suitable for use by security-conscious companies.

There are various methods in use today for lie detector UK testing, including personal interviews (lie detection by observation), integrity tests, voice stress analyzers, micro expression software, electroencephalogram, fMRI, and others.


The test for ocular motor deception (now known as EyeDetect) was originally developed around 2002, by two researchers from University of Utah. University of Utah.

It’s a computer-driven system that has a high-definition eyes-tracking camera that tracks eye movements like pupil dilation eyes movements (fixations) and blink speed during the 15-30 minute test in which the test participant answers the questions using the computer mouse.

Eye behavior and test results are collected and analyzed by a computer algorithm in order to calculate the credibility score.

EyeDetect offers many features that are similar to polygraph, as its creators have expertise in polygraph.

EyeDetect tests are automated and standardized. They score without any involvement from a human examiner, aside from testing preparation. There are no sensors or other devices are connected to the individual taking the test.


The instrument for polygraphs was initially developed around 1920. In essence, it’s an instrument that monitors the changes that occur in three kinds of physiological activity: (1) cardiovascular activity like blood pressure and heart rate, (2) respiratory activity and (3) conductance of the skin.

The polygraph was initially an analog device, but was updated in the late 1990s to be more digital which is currently software-driven.

The cardiovascular activity is monitored using an instrument for measuring blood pressure similar to one you’ve seen at the doctor’s office. The intensity and frequency of breathing are recorded by tube-shaped sensors , which are connected to the chest and abdomen.

The conductivity of the skin, or resistance which is also known by the term electrodermal, can be measured using small electrodes attached to finger using a small glue as well as Velcro wraps.

The majority of polygraph examiners include a motion sensor that is attached to the chair that is used for testing a person. It detects small movements of the trunk, legs and feet.

Tests based on polygraphs rely on examiners to ask questions and assess test scores.

Test Format

The recording of changes in physiological function as well as the responses to questions is recorded as part of EyeDetect and polygraph tests. Both systems come with the pre-test that follows by the test for lie detection. Both tests come with exercises to make the test subject familiar with the questions and their format.

Note: A person who has to take the lie detector test is known as”examinee. “examinee.”

Before taking the test using EyeDetect The test taker watches an audio-visual demonstration of the subject matter to be tested and is provided with instructions on “how” this test is administered.

Similar to the polygraph test the test taker is given instructions from the examiner regarding “how” it will be conducted and the test questions are discussed to ensure that the person taking the test understands the purpose that the examination will cover.

The tests can also be preceded by a test procedure known as an acquaintance test or stimulation. This test can be used as an opportunity to test the device’s reliability in order to provide the user with confidence in the device.

The tests contain questions on the subject matter. Refer to for the “Test questions” Section below for further information.

Test Protocols

Two test protocol are that are used for EyeDetect or polygraph testing: (1) screening tests and (2) tests for diagnosing.

Screening tests are that are conducted without an incident or allegation that is known and are generally based. They can ask the test taker about a range of target behavior or may focus on one specific issue that is of significance. These target behaviors may include theft, use of drugs and fraud, bribery and domestic violence, among others.

Screening tests are typically employed as a pre-employment screening test of applicants for jobs in addition to a follow-up exercise for employees currently employed.

Diagnostic tests are performed in the event of a known incident or allegation . They include questions that are specific to an incident, for example, the robbery of a bank sexual assault, a bank robbery, or the homicide. These kinds of tests are typically employed in civil or criminal instances.

Test Questions

Tests for eye detection and polygraph contain “relevant” questions that focus on the behavior of the target or the issue of concern.

Have you taken illegal substances within the last 90 days?
Did you smuggle any cash out of your account at the 1st National Bank last week?

There are as well “comparison” questions that are not related to the behavior of the test subject or subject of concern. These questions are intended to establish an appropriate reaction in the event that the examiner is being honest or to provide a different set of questions to test the examiner’s aim of passing the test.

If a person doesn’t react strongly to questions on comparison however, they do react strongly to the relevant questions the two systems may make a suggestion that they are lying.

Psychology of Testing

When testing for lie detectors test, the participants are most focused on being able to pass the examination. If someone fails the test to detect lies and is found to be ineligible, they may lose their job, and not be hired, end up in jail, divorced, etc.

A true-to-lifer will be worried about following instructions and answering every question truthfully. A true-to-life person doesn’t want to be a failure on the test due to any reason that is not related to the truth.

A person who is a liar will be worried about looking innocent and answering the questions in a manner that causes the least amount of physiological response. Every person is driven to succeed in the test.

Both tests show when there is a more physiological response to the relevant questions in comparison to questions of the same type the test subject is believed to be deceiving.

If an examinee exhibits an increased physiological response to questions of comparison than relevant questions, the test subject is believed to be harmless.

If no or little distinction is found in the response of the examiner to the relevant questions and those that compare The test results may be classified as “inconclusive.” That is to say, the test taker’s response seemed to be neither innocent or guilty.

Test Scoring

The tests for eye detection are scored with an algorithm developed by computers. Information about eye behavior and test response are used to calculate the creditability score within minutes of the test’s conclusion.

Polygraph tests are graded by examiners who’ve received instruction in reading and interpreting the physiological responses. Polygraph instruments also rely on algorithms that aid the examiner.

Accuracy of Test

The accuracy of polygraph and EyeDetect has been tested in numerous lab experiments under controlled conditions using “ground fact.” According to definition ground truth is the term utilized in research studies that reveal the exact number of lab participants are assigned to the “innocent” or “guilty” circumstance.

The guilty participants are required to take part in a mock or simulated crime during the research, whereas those who are designated as innocent are not required to commit any mock crime. Both groups are subjected to the same test.

The results of lab studies for Polygraph and EyeDetect have appeared in journals of science and peer-reviewed in a number of cases.

Despite the findings from scientific studies certain physiological reactions might not be exclusive for liars and truthtellers. A truthteller might be nervous, anxious or distracted during a test and could exhibit symptoms of an reaction that are typically experienced by those who are guilty.

If the truthteller fails to pass an examination, it is known as a false positive (FP) results. If a lieder fails a test, this is known as a false negative (FN) outcome. For EyeDetect or polygraph, they is a margin of error. Both have been demonstrated to reduce FPs in addition to FNs.


A few examinees attempt at “fool” to fool the test by employing countermeasures. Countermeasures are actions that a person takes to defy or alter the test.

Countermeasures can be found in physical activity, mental exercise or taking drugs. Countermeasures’ purpose is to alter changes in the body in order to alter the results of tests.

In the instance of EyeDetect the changes in eye behavior that are observed during questions are due to increased cognitive load. They are also involuntary. They are uncontrollable.

Additionally, the rapid time of the questions asked during the EyeDetect test makes implementing an effective countermeasure difficult.

There are various methods in use today for lie detector testing, including personal interviews (lie detection by observation), integrity tests, voice stress analyzers, micro expression software, electroencephalogram, fMRI, and others.

In addition to EyeDetect and polygraph These other methods are usually lower than 80 percent precise expensive or extremely invasive and uncomfortable to the test subject.