What is the Control Question Techniques & Other Methods in Lie Detector Testing?

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In the realm of detecting deception, lie detector testing has long held a place of intrigue. One of the key approaches employed in these tests is the Control Question Technique (CQT), alongside other methods. By examining physiological responses, such as heart rate and perspiration, polygraph examiners attempt to distinguish truth from falsehood. In this blog post, we delve into the principles behind these techniques and explore their application in lie detector testing.

What is the Control Question Techniques?

The Control Question Technique (CQT) is a widely used method in lie detector testing. During a CQT examination, the polygraph examiner asks a series of questions that provoke physiological responses in the person being tested. These questions include relevant questions directly related to the issue being investigated and control questions unrelated to the specific issue.

The purpose of control questions is to elicit a stronger physiological response from a deceptive individual. By comparing the person’s reactions to relevant and control questions, the examiner aims to determine the truthfulness of the responses based on the differences in physiological arousal.

Why Is It Necessary For A Polygraph Test?

The use of a polygraph test, including techniques like the Control Question Technique (CQT), is considered necessary in certain contexts for several reasons:

Investigative Aid

Polygraph tests can serve as an investigative tool, assisting law enforcement agencies and government organizations in gathering information during criminal investigations or security screenings. The test results can provide additional insights and help guide further inquiries.


The mere presence of polygraph testing can act as a deterrent, discouraging individuals from attempting to deceive or engage in dishonest behavior. The possibility of being subjected to a polygraph examination can influence behavior and encourage truthfulness.

Screening Candidates

In certain professions, such as law enforcement, intelligence agencies, or sensitive government positions, polygraph tests are utilized to screen candidates for their suitability and trustworthiness. The tests help identify individuals who may have integrity issues or are prone to deception, minimizing potential risks.

Gathering Additional Information

Polygraph tests can be employed to elicit additional information or confessions from individuals involved in an investigation. The test may serve as a tool to encourage individuals to disclose relevant details or admit to their involvement in a particular event.

Understanding Control Questions and other methods on a Polygraph Test

Control Question Techniques and other methods are used in lie detector testing, also known as polygraph examinations, to help determine the truthfulness of a person’s responses. While the accuracy and reliability of polygraph tests have been a topic of debate, these techniques are commonly employed in the field. Here are some of the main methods used:

Control Question Technique (CQT)

The CQT is one of the most widely used techniques in polygraph testing. It involves asking a series of questions that are designed to measure a person’s physiological responses (such as heart rate, blood pressure, respiration, and sweat gland activity) while they answer relevant questions and control questions. Control questions are unrelated to the specific issue under investigation but are designed to provoke a physiological response from someone who may be attempting deception. The polygraph examiner then compares the person’s reactions to relevant questions with their reactions to the control questions.

Relevant/Irrelevant Technique (RIT)

The RIT is an older technique that has been largely replaced by the CQT. In this technique, the polygraph examiner asks a mixture of relevant questions (directly related to the issue being investigated) and irrelevant questions (unrelated to the issue). The assumption is that a deceptive person will exhibit stronger physiological responses to the relevant questions compared to the irrelevant ones.

Guilty Knowledge Test (GKT)

The GKT is a technique used when the polygraph examiner has specific knowledge about the crime or event under investigation. The examiner asks multiple-choice questions, one of which contains information that only the guilty person would know. The theory is that a guilty person’s physiological responses will indicate recognition of the details that only the perpetrator would possess.

Concealed Information Test (CIT)

The CIT is similar to the GKT but does not require prior knowledge of specific details. The polygraph examiner presents multiple-choice questions, including one that contains information that is only known to the perpetrator. The physiological responses to these questions are then compared to responses to control questions to determine if the person has concealed knowledge.

Comparison Question Test (CQT)

This technique is similar to the CQT but focuses on comparing the physiological responses to relevant and comparison questions rather than control questions. The comparison questions are designed to be less threatening and may be used as a baseline for comparison.


Lie detector testing, employing the Control Question Technique and other methods, has been utilized for decades as a tool to uncover potential deception. While the accuracy and reliability of such tests remain a topic of debate, they continue to find applications in certain domains. Understanding the fundamentals of these techniques provides valuable insights into the mechanisms involved in polygraph examinations. As advancements in technology and psychological research progress, we may witness the evolution of lie detection methods and the refinement of our understanding of human deception.

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