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How Lie Detector Tests Work

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The majority of lie detectors are instruments that monitor changes in the parts of the physiology of an individual when they answer questions. The concept is that if someone responds differently to specific types of questions, that individual can be determined either innocent or guilty. If the person’s response is not considered innocent or innocent, this is referred to as an inconclusive outcome.

Over time, lab and field research has revealed that most liars have similar patterns of change with regards to physical behaviors that sensors can detect. Of of course, there are instances that liars don’t exhibit the same physical characteristics as the majority. This is why lie detectors are able to detect a margin of error.

This page will concentrate on two test to detect lies:

(1) EyeDetect(r)

(2) Polygraph

The two devices were demonstrated by field and laboratory research to possess more than 80% precision in detect deceit. If a lie detector device achieves at least 80% accuracy or better and is therefore not suitable to be used by the majority of security-conscious companies.

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.


The test for ocular motor deception (now known as EyeDetect) was initially developed at the beginning of 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, blink rate, eye movement (fixations) and blink rate in tests of 15 to 30 minutes where a person has to answer the questions using an electronic mouse.

Eye movements 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 know polygraphs well.

EyeDetect tests are automated and standardized. They score without any involvement from a human examiner other than the preparation of the test. No sensors or other equipment are connected to the person who is being evaluated.


The instrument for polygraphs was invented during the 20th century. In essence, it’s an instrument to record the variations in three categories of physiological activity: (1) cardiovascular activity like blood pressure and heart rate, (2) respiratory activity and (3) conductance in 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.

For help with a lie detector test in the UK visit

The cardiovascular activity is monitored using an instrument for measuring blood pressure similar to one you’ve seen at the doctor’s office. The frequency and depth of breathing is measured using tubes-shaped sensors that are attached to the chest of a person’s abdomen.

The conductivity of the skin, or resistance which is also known as electrormal activation, is determined by tiny electrodes that are attached to finger with a tiny sticky as well as Velcro wraps.

The majority of polygraph examiners include a motion sensor that is attached to the chair to test a person. The sensor can detect subtle movement in the trunk, legs and feet.

Tests based on polygraphs rely on examiners to answer questions and score tests.

Test Format

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

Note: The person who must take an examination for lying is known as”examinee. “examinee.”

Before testing using EyeDetect Examiners watch an audio-visual overview of the subject matter to be tested and is provided with instructions on “how” this test is administered.

Similar to the polygraph test an examinee receives instructions from the examiner regarding “how” this test is administered and questions for the test are reviewed to make sure the test taker is aware of the purpose and purpose of the exam.

The tests can also contain a pre-test process, referred to 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 topic of interest. Refer to for the “Test questions” Section below for further information.

Test Protocols

The two protocols for testing are to conduct EyeDetect or polygraph testing: (1) screening tests and (2) tests for diagnosing.

Screening tests are tests that are carried out in the absence of an incident or allegation that is known and are of a general nature. They can ask the test taker about a variety of targeted behaviours or focus on one specific issue that is of particular concern. The target behaviors can include theft, use of drugs and fraud, bribery and domestic violence, among others.

Screening tests are commonly utilized as a pre-employment test of prospective employees in addition to a follow-up exam for employees currently employed.

Diagnostic tests are performed in the event of a known incident or claim and contain questions that are specific to an incident, for example, an armed robbery at a bank sexual assault, bank robbery or murder. These kinds of tests are typically utilized in civil or criminal instances.

Test Questions

Polygraph and EyeDetect tests have “relevant” questions that are designed to address the target’s behavior or topic of importance.

* Have you ever used illegal substances in the last 90 days?
Did you steal any cash out of you at 1st National Bank last week?

There are additionally “comparison” questions that are not related to the intended behavior or topic of concern. These questions are intended to determine an appropriate reaction in the event that the examiner is lying or offer a different set of questions that challenge the test taker’s intention of passing the test.

If someone does not react strongly to questions on comparison however, they do react strongly to the relevant questions and both systems could provide a conclusion 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 they fail the test of lying detectors it could mean they be fired, but not get hired, be sent to jail, divorced, etc.

A true storyteller is focused on following directions and answering every question truthfully. A truthteller will not want to be a failure on the test due to any reason that is not related to the truth.

A liar is anxious about appearing innocent while answering the pertinent questions with only a minimal reaction to their body. Every person is driven to succeed in the test.

For both of the tests when there is a higher 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 the comparison question than to relevant questions, the test subject is believed to be harmless.

If there is no significant distinction is found in the response of the examiner to questions that are relevant or comparison The test results may be classified as “inconclusive.” This means that the test subject’s behavior was not innocent or guilty.

Test Scoring

Tests for EyeDetect are graded using an algorithm that is computer-generated. The data relating to eye movements and test results are used to calculate the creditability score within minutes after test the test’s completion.

Tests for polygraphs are scored by examiners who’ve received training in the ability to read and interpret the physiological responses. Polygraph tests can also depend on algorithms to aid the examiner.

Accuracy of Test

The accuracy of both EyeDetect and Polygraph have been evaluated in a variety of laboratory studies in controlled conditions using “ground fact.” According to definition ground truth is a term utilized in laboratory studies in which researchers can determine that they know with absolute certainty which lab participants have been assigned either an “innocent” or “guilty” situation.

People who are deemed guilty are required to take part in a mock or simulation crime in the laboratory research, whereas those who are designated as innocent participants do not 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 results from scientific studies some physiological reactions may not be exclusive for liars and truthtellers. A truthteller might be nervous, anxious, or distracted when tested , and may exhibit the signs of a reaction commonly observed in criminals.

If an honest person fails 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 as well as polygraphs, both is a margin of error. However, both have been proven to reduce FPs in addition to FNs.


A few examinees attempt at “fool” to fool the test by employing countermeasures. Countermeasures are the actions performed by an individual to defy or discredit the test.

Examples of countermeasures are physical activity, mental exercise or taking drugs. Countermeasures’ goal is to alter changes in the body to influence the test results.

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 not controlled.

Furthermore, the speedy 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 not more than 88% reliable expensive or very injurious and uncomfortable to the person who is being examined.