A polygraph, commonly known as a lie detector, is a device used to measure and record several physiological responses simultaneously. It is most famously used in forensic settings, such as during criminal investigations or in certain employment screenings, to determine the truthfulness or deception of someone’s statements.
How it works
The polygraph measures various physiological indicators, including changes in blood pressure, heart rate, respiration rate, and skin conductivity. Sensors attached to the subject’s body capture these measurements while the subject answers a series of questions.
The underlying principle of the polygraph test is that observable physiological changes occur when a person is being deceptive. The polygraph technician analyses the data recorded by various sensors to identify patterns that may indicate a subject is lying.
Conducting a Polygraph Test
During a polygraph test, the subject is typically asked a series of questions, including control questions and relevant questions.
Control questions are designed to establish a baseline for the person's physiological responses.
Relevant questions are directly related to the issue under investigation.
The theory behind the psychological mechanism of polygraph tests is that when someone lies, they experience a surge in stress or anxiety, which leads to observable physiological changes such as an increase in heart rate, blood pressure, and sweating, or alterations in breathing patterns.
The polygraph technician interprets the recorded data, looking for significant deviations or patterns that may indicate deception. However, it is important to note that the interpretation of the results is subjective and relies on the expertise of the examiner.
Potential Shortcomings of the Polygraph
There are several potential flaws associated with polygraph tests:
Variability in Physiological Responses: People have different responses to stress and anxiety. Some people may naturally exhibit heightened physiological arousal even when telling the truth, making it difficult to establish a reliable baseline or accurately assess deception.
Countermeasures: If subjects are aware of the intricacies of the polygraph, in order to respond undetected they may employ countermeasures to manipulate their physiology and deceive the test.
Lack of Standardization: No universally accepted standard for polygraph testing procedures exists. People use different techniques and methods and interpret sensor results differently. This lack of standardization reduces the overall reliability of results.
Psychological Factors: The subject’s mental state, anxiety levels, or motivations can influence the polygraph test results. Namely, emotional distress and fear can impact their physiological responses, potentially leading to misleading outcomes.
Considering these potential flaws, experts argue that polygraph tests should not be considered as conclusive evidence of a lie. Polygraph tests should be used cautiously, if at all, in legal or employment contexts. Their results should be considered alongside other evidence rather than being relied upon as the only proof of possible deception.
Learn more about polygraphs here!
Reference List
HowStuffWorks. (2021). How does a Lie Detector (Polygraph) Work? [online] Available at: https://science.howstuffworks.com/question123.htm [Accessed 9 Jan. 2024].
Polygraphis.com. (2023). Sample Polygraph Chart. [online] Available at: https://www.polygraphis.com/AmericanInstitute/chartsample.htm [Accessed 9 Jan. 2024].
Commentaires