There really is no such thing as a lie detector. But, there are various instruments today that measure aspects of physiological changes, which scientists have associated with lying (deception).
When certain physical changes occur during a lie detector test—under controlled conditions while questions are asked—a person may appear “guilty” based on their physiological reaction.
Some physiological changes measured during lie detector testing include:
| • Heart Rate | • Pupil Dilation | • Body Movements |
| • Blood Pressure | • Eye Fixations | • Leg Movements |
| • Respiration | • Blink Rate | • Question Response Time |
| • Skin Conductance | • Brain Activity | • Question Error Rate |
Through scientific studies conducted with EyeDetect, specific physiological changes have been shown to be similar among liars. This means EyeDetect can be an effective lie detector test. In fact, it is the most accurate lie detector today.
Note: There is no perfect lie detector test. All tests have a margin of error. They can give false-positive results and false-negative results. EyeDetect minimizes false positives (when an innocent person looks guilty).
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• It takes more thought to create bogus dates, times, places and people.
• It takes more thought to maintain consistency and believability in a fake story.
• It takes more thought to monitor behavior when questioned—to keep things believable.
Today’s Lie Detector Tests
Most organizations rely on one, some, or none of the following lie detector testing methods:
• Personal interview
• Personality test
• Integrity test
• Voice stress analyzer
• Electroencephalogram
• fMRI
• Polygraph
• EyeDetect (ocular-motor test)
Research shows most lie detector test solutions have “issues.”
• Personal interview = 54% accurate at detecting deception
• Personality test = do not measure or detect deception
• Integrity test = up to 64% accurate at detecting deception
• Voice stress analyzer = 65% accurate at detecting deception
• Electroencephalogram = 87% accurate at detecting deception, but very invasive
• fMRI = 72% accurate at detecting deception, but very costly
• Polygraph = one of the most accurate, but exams are expensive, take time, are invasive, and are difficult to keep a safe social distance
Human Lie Detector Test
Because of movies and TV shows, most people think liars avoid eye contact, cover their mouths, make mistakes when speaking, touch their body, fidget, etc.
Studies show these behaviors are not reliable indicators of deception.
Why? A skilled liar can respond to tests questions with a high degree of accuracy, which makes them seem believable. But, giving correct answers does not prove innocence.
For example, if a parent found their 5-year-old child in the kitchen eating cookies and asked, “Are you eating cookies?” The typical child would answer, “No.” And, “no” is the answer expected from someone being tested, but the child is obviously lying about eating cookies.
Although human lie detectors are generally inaccurate at detecting deception, there are a few verbal cues that liars tend to exhibit when telling a concocted “story.”
Those verbal cues common to liars include:
• Use of more negative statements
• Give shorter responses, i.e., don’t want to tell you much
• Give explanations that are not very believable
• Make fewer self-references to keep themselves out of the story
• Change the subject – avoidance or deflection
• Distance themselves from others involved
• Give inconsistent facts
• Tend to memorize their story and give it verbatim each time asked
Source: Vrij, 2008
Challenges with Some Lie Detector Testing Methods
Organizations commonly rely on a favorite lie detector testing method such as those previously mentioned. Here is a brief description of each of those lie detector tests and their reported rates of accuracy.
Concerned about being believed, liars often seem helpful and truthful in an interview, and put more effort into impressing their interviewer. Because of that, personal interviews are not very accurate at detecting deception.
>> Accuracy in the detection of deception: 54%
>> Source: Bond & DePaulo, 2006
These tests do not measure deception.
They are used to see if a person is a good fit in the company culture or if there is a good fit from a behavioral perspective. As such, there is no reported rate of accuracy at detection deception.
A study conducted by researchers in 2012 evaluated over 100 integrity tests from test publishers and non-publishers to determine if they were accurate at predicting job performance, training performance, counterproductive work behavior (such as substance abuse, theft, withdrawal, etc.) and employee turnover.
These tests have a low predictive value for behavior. Most data are gathered from self-reporting participants, who easily fake their responses.
>>Accuracy in the detection of deception: 53-64%
>>Source: The Criterion-Related Validity of Integrity Tests, Journal of Applied Psychology, 2012.
This lie detector testing method is based on the premise that small, involuntary frequency modulations occur in the voice when under the stress of lying. Essentially, muscles in the voice box tighten or loosen, which changes the sound of the voice.
A precision instrument must be used to measure these slight frequency modulations. They cannot be heard with a human ear. But, the accuracy slightly better than tossing a coin.
>>Accuracy in the detection of deception: 50-65%
>>Source: Journal of Forensic Sciences, 53(1), 183-193, 2008.
Using probes attached to a person’s skull, the EEG measures electrical activity at the surface of the brain. It compares familiar and unfamiliar stimuli (i.e., the person sees a friend vs. a stranger). The comparisons are used to determine when someone is lying.
>>Accuracy of the EEG in the detection of deception: 87%
>>Source: various research papers
Using powerful magnets to charge hydrogen protons within cells, the fMRI translates radio frequencies that are absorbed or reflected into an image of the area of the brain scanned. A map is created of pattern vectors associated with specific cognitive states.
A radiologist predicts the cognitive state by observing these patterns and looks at changes in whole-brain patterns to predict the cognitive state the brain is experiencing.
>>Accuracy in the detection of deception: 72%
>>>Source: National Academy of Sciences, February 2014.
An instrument that gathers multiple signals from sensors connected to a subject. Data includes cardiovascular, respiratory, and electro-dermal activity. In simple terms, it comes down to respiratory activity, blood pressure, and sweat / skin conductance. Measurements are recorded and analyzed to detect these physiological changes and correlate them with the statements made about the questions.
>> Accuracy in detecting deception: 87%
>> Source: American Polygraph Association Meta-analytic survey, Table 2, 2011.
A computer with a high speed, precision eye tracker measures involuntary changes in the eyes and reading behaviors while a person answers true / false questions. These measures have been shown to be associated with increases in cognitive load, which have been associated with deception.
>> Accuracy in detecting deception (screening test): 91%
>> Source: J. Kircher (2021). EyeDetect Hybrid Multi-Issue Comparison Test (HMCT) Development and Validation Summary
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