Polygraph Test Explained: How It Works, Accuracy, and 10 MCQs

Understand the polygraph test, its process, and limitations. Learn about its accuracy and common misconceptions. Test your knowledge with 10 multiple-choice questions.

Purpose

A polygraph test, often colloquially referred to as a "lie detector" test, is a procedure that measures and records physiological changes in a person's body while they answer a series of questions.

The underlying assumption is that deception elicits distinct physiological responses compared to truthful statements. The primary purpose of polygraph testing is to assess the veracity of a person's statements, often in criminal investigations, pre-employment screenings, or security clearances.  

A polygraph machine records several physiological indicators, including:

• Heart rate and blood pressure: Changes in cardiovascular activity can be associated with emotional arousal.  
• Respiration: Breathing patterns may alter under stress or deception.   
• Skin conductivity: Increased perspiration can indicate emotional arousal.

The test typically involves three phases:

1. Pre-test interview: The examiner establishes rapport with the subject, explains the test procedure, and collects background information.  
2. Stimulus presentation: The examiner asks a series of questions, including relevant questions pertaining to the investigation and control questions designed to establish a baseline of physiological responses.  
3. Post-test interview: The examiner analyzes the recorded data and may conduct an interview to clarify responses or gather additional information.

The examiner interprets the physiological data in conjunction with the subject's verbal and nonverbal behavior to reach a conclusion about the likelihood of deception.

Limitations

It's crucial to understand that a polygraph test is not infallible. Several factors can influence the accuracy of the results:

• Subject countermeasures: Individuals can intentionally manipulate their physiological responses to deceive the examiner.
• False positives: Innocent individuals may exhibit physiological responses consistent with deception due to anxiety or other factors.
• False negatives: Deceptive individuals may not show significant physiological changes.
• Subjectivity: The interpretation of polygraph data relies on the examiner's expertise and judgment.

Due to these limitations, polygraph results are generally inadmissible as evidence in court in many jurisdictions.  

Multiple-Choice Questions

1. What is the primary purpose of a polygraph test?

   • a) To measure intelligence
   • b) To assess a person's veracity
   • c) To diagnose psychological disorders
   • d) To predict future behavior
   • Answer: b

2. Which of the following is NOT typically measured by a polygraph machine?

   • a) Heart rate
   • b) Blood pressure
   • c) Brain activity
   • d) Respiration
   • Answer: c

3. The belief that deception causes distinct physiological responses is the underlying principle of:

   • a) Polygraph testing
   • b) Psychoanalysis
   • c) Hypnosis
   • d) Behavioral analysis
   • Answer: a

4. What is the term for questions designed to establish a baseline of physiological responses in a polygraph test?

   • a) Relevant questions
   • b) Control questions
   • c) Irrelevant questions
   • d) Diagnostic questions
   • Answer: b

5. Which of the following is a common criticism of polygraph tests?

   • a) They are highly accurate
   • b) They are inexpensive to administer
   • c) They are not admissible as evidence in court in many jurisdictions  
   • d) They are not susceptible to countermeasures
   • Answer: c

6. The interpretation of polygraph data is primarily based on:

   • a) A computer algorithm
   • b) The examiner's expertise
   • c) The subject's confession
   • d) Random chance
   • Answer: b

7. False positives in polygraph testing refer to:

   • a) Deceptive individuals who pass the test
   • b) Innocent individuals who fail the test
   • c) Errors in the polygraph machine
   • d) The examiner's misinterpretation of data
   • Answer: b

8. Which of the following can influence the accuracy of a polygraph test?

   • a) Subject's anxiety level
   • b) The examiner's experience
   • c) The type of questions asked
   • d) All of the above
   • Answer: d

9. Polygraph results are generally considered to be:

   • a) Conclusive proof of guilt or innocence
   • b) Highly reliable and accurate
   • c) Admissible as evidence in all courts
   • d) Subject to interpretation and potential error
   • Answer: d

10. The use of polygraph tests is most common in:

    • a) Criminal investigations
    • b) Medical diagnosis
    • c) Educational settings
    • d) Marketing research
    • Answer: a