What is a Polygraph Machine?
A polygraph machine, commonly known as a lie detector, is a device that measures a person’s physiological responses to determine if they are telling the truth. It doesn’t directly detect lies but records signs of stress or anxiety, which are often associated with deception.
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How Does a Polygraph Machine Work?
The polygraph machine records various physiological activities:
1. Respiration: Measures breathing patterns using sensors placed around the chest.
2. Heart Rate and Blood Pressure: Monitored using a blood pressure cuff.
3. Galvanic Skin Response (GSR): Detects changes in skin conductivity caused by sweating.
4. Body Movements: Tracks movements that might indicate nervousness or an attempt to manipulate the test.
The examiner begins by asking baseline questions to establish normal physiological responses. Then, a series of relevant and control questions are asked. If the responses to relevant questions differ significantly, it may indicate deception.
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Where is the Polygraph Used?
1. Law Enforcement: For investigations and verifying testimonies.
2. Employment Screening: Especially in government or high-security jobs.
3. Research: Used in psychology and behavioral studies.
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Limitations of the Polygraph
1. Accuracy Concerns: Studies suggest its accuracy ranges from 70% to 90%.
2. False Results: Nervous individuals may appear deceptive, while skilled liars may pass as truthful.
3. Legal Admissibility: Many countries do not accept polygraph results as legal evidence due to reliability concerns.
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Conclusion
A polygraph machine can be a useful tool for detecting deception, but it is not foolproof. It should only be used as a supportive device alongside other evidence.
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