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Writer's pictureScience Holic
Oct 31, 20204 min read

Lie Detectors: Are they reliable?

Author: Brianna Hang

Editors: Tharindi Jayatilake and Anand Soma

Artist: Uzouf Baagil

Do you solemnly swear to tell the truth, the whole truth, and nothing but the truth? In almost every crime show, the suspect would be sweating profusely in the interrogation room as the detectives hook him up with a polygraph to determine if he is guilty or innocent. A lie detector, otherwise known as a polygraph test, is a device that measures several physiological indicators such as blood pressure, heart rate, respiration, and skin conductivity. The earliest version of the lie detector test was created in 1921 by John Larson, and as technology constantly grows, the new computerized model continues to monitor the same measures in the past. However, there has been some debate regarding whether or not lie detectors are reliable as there are no specific physiological reactions associated with lying.

Polygraphs are constantly being used by law enforcement and it is mostly used to measure fear and nervousness based on main physiological indicators. Investigators created a technique that is still widely used today called the “Control Question Technique”. The interrogator would mix control questions from non-threatening and random questions that aren't related to the case to relevant questions pertaining to the case. By using this technique, it would create some anxiety for the suspect because they would have to tell the truth with vague questions. Although, it has been shown that even innocent people can have greater levels of nervous activity due to the circumstances they are in especially if they got accused of a crime. According to the Psychological Set Theory, a person getting tested anticipates negative consequences if he/she lies, so their body produces a certain measure of physiological reactions that could signal deception. Another procedure investigators use is the “Guilty Knowledge Test” which is a multiple-choice test that has the information only the guilty person would know. However, this procedure is rarely used because the investigators don’t always have enough information to create the test.

Another flaw could be in the other factors that might have occurred without law enforcement knowing about it. This was created based on the Oriental Response Theory, or the oriental response, which is the organism’s response to a change in its environment that creates an adaptive response to the stimulus. The oriental response is subject to habituation where the subject can familiarize and prepare themselves with the questions that could lead to invalid results. According to the American Psychological Association, “A particular problem is that polygraph research has not separated placebo-like effects (the subject’s belief in the efficacy of the procedure) from the actual relationship between deception and their physiological responses." Subjects who believe the lie detector test works tend to confess more easily or become more anxious, thus providing a lower accuracy rate for determining lies. There are also possible countermeasures that can help block certain physiological responses such as using drugs that alter arousal, psychological manipulation, and small physical movements. Overall, the polygraph test is mostly used to detect the anxiety levels connected to the physiological responses which give clues of deception; however, it is not always accurate for every person.

There has also been a new study involving the updated version of the lie detector test through brain scans and imaging. The near-infrared brain scan is a headband that emits near-infrared light into the subject's prefrontal cortex where most of the decision-making occurs. The sensors can detect the changes in blood flow once the subject decides to lie even before they get to say it. The device is currently under development because researchers are still gathering data from subjects who answer the control questions truthfully or not. In addition, functional magnetic resonance imaging (fMRI) has already been used to detect brain abnormalities; however, studies based on the fMRI show that the anterior cingulate cortex and the superior frontal gyrus light up more when a person tells a lie than telling the truth. These regions of the brain are associated with emotional processing, decision-making, and conflict resolution. Lying can impact these regions through higher levels of anxiety because they have to quickly think of a response to the question and try to process their emotional state. The fMRI can be improved with the transcranial magnetic stimulation that enhances or blocks out certain activities in the brain to improve the accuracy of the lie detector. Another new procedure used was brain-fingerprinting through an electroencephalogram (EGG), a helmet with electrodes attached to the head to record changes in electrical activity in the brain. A P300 pattern, a specific brain wave, is elicited when the subject knows the information but chooses to lie about it. This happens when the brain believes the information is important or surprising to the subject. However, similar to the flaws of the polygraph, drugs or medications can affect the brain waves and it can only be used once the investigators have enough information about the case. Overall, rather than trying to detect the physiological responses, looking for certain brain wave patterns could be more useful because other factors such as anxiety and the placebo effect can create false negatives for the subjects. As a result, some court cases hesitate to accept lie detection tests as admissible evidence due to its uncertainty of testing for deception.

Overall, the lie detector test has high reliability considering it is widely used in law enforcement; however, there are still concerns about its validity and accuracy of the test. Not only are innocent people victim to the psychological and physiological turmoil, but the guilty are free to roam the earth. Researchers are still trying to develop new devices to detect lying, but it might not happen until the far future as we continue to use the same methods from the past. And in the words of Benjamin Franklin, “half a truth is often a great lie”

 

Citations:

Gonzalez, Nora. “Do Lie Detectors Actually Work?”. Britannica.

Tancredi, R. Laurence. “The New Lie Detectors”. Scientific American. 15 April 2005:

Hart, L. Christian (Ph.D.). “Do Lie Detector Tests Really Work?”. Psychology Today. 14

Cino, G. Jessica. “Is a polygraph a reliable lie detector?”. Phys Org. 1 October 2018:

Baran, Madeleine and Vogal, Jennifer. “Inconclusive: The truth about lie detector tests”.

American Public Media. 20 September 2016:

September 2020

The Truth ABout Lie Detectors (aka Polygraph Tests). American Psychological Association. 5

August 2004: https://www.apa.org/research/action/polygraph. 21 September 2020

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