When a medical student and police officer announced his invention of a lie detector machine back in 1921, the world was mesmerized. Marketers, movie producers and newspapers capitalized on the fervor by promoting the device, which eventually was referred to as a polygraph, in advertisements, headlines and even movies like the 1926 film Officer 444.

Described as a “cardio-pneumo psychogram,” worked by providing readings of a person’s blood pressure — supposedly a true indicator of whether a person cuffed to it was being truthful or was lying.

Since then, his polygraph test has undergone numerous evolutions to improve its accuracy in use in cold case investigations. 


Much like in the 1920s, the polygraph also has served as a source of entertainment in today’s world, particularly with sensational TV programs like The Maury Show which brings in guests who want to find out if a person is lying about cheating, a child’s paternity or other affairs of the heart. Once the polygraph results are revealed, the participants on the show — as well as the audience — take them as the undeniable truth and, of course, emotional responses erupt, both good and bad.

However, throughout its 100-plus year history, the polygraph has been under scrutiny — especially in court cases. Even though polygraph tests are touted as science, many psychologists, judges and other legal officials aren’t confident in its accuracy. 

The American Psychological Association (APA), citing psychologist Leonard Saxe, said “that the idea that we can detect a person’s veracity by monitoring psychophysiological changes is more myth than reality.” APA went on to say that “even the term “lie detector,” used to refer to polygraph testing, is a misnomer. So-called “lie detection” involves inferring deception through analysis of physiological responses to a structured, but unstandardized, series of questions.”

For that reason, outside of TV shows, the polygraph is used primarily in non-judicial settings, such as determining the accuracy of statements made by witnesses and suspects in police investigations (outside the courtroom) and prospective employees for private companies.


Formulating polygraph questions

If you’re ever in a situation where you would undergo a polygraph exam, whether it’s for an employment screening, a legal process or for an appearance with TV host Maury Povich, a forensic psychophysiologist is the professional who will conduct your test.

This individual must have a background in criminal justice and/or police work. In addition, they must have completed more than 200 hours of training at an American Polygraph Association (APA) academy, along with 200 additional hours of exams, followed by APA certification. 

One of the most important aspects of polygraph preparation is preparing the questions, according to the American Polygraph Association.

The American Polygraph Association, in a journal article, points out that it can be detrimental for a test administrator to stick to a prepared list of questions. In some cases, the subject may not understand the question and may be afraid to admit that they don’t. 

The polygraph also should start with questions that establish a baseline. When working with investigators or attorneys on a case, for example, you can ask them to suggest a question that can be answered with a “yes” or a “no.” Multiple choice questions can lead to more errors, according to the association.


Types of questions needed for an effective polygraph:

  1. Relevant questions: These types of questions are relevant to the case. Using information gathered from pre-polygraph questioning with police officers or attorneys, for example, the examiner will ask relevant questions about an abduction. The question may simply be “Did you abduct the victim?,” which would demand a “yes” or a “no” response.


  1. Control/comparison questions: This line of questioning, which is often described as a Control Questions Test or CQT, is typically administered in several phases. Using the relevant questions as a comparison (“Did you abduct the victim?), the examinee will ask “control” questions that are more general, i.e. “Have you ever betrayed someone’s trust?” 


  1. Probable lie control/comparison questions: These questions are treated as relevant questions, according to the American Polygraph Association, but they are broader in scope than the relevant topics — typically similar to the crime but less severe. Again, the person undergoing the test should be able to simply answer these questions with a “yes” or a “no.”


  1. Irrelevant questions: These types of questions, which can be interspersed throughout the test, are used as a baseline or to help reduce any nervous tension. They can be as simple as confirming the identity of the person being tested. According to the association, there are two types of irrelevant questions. One is more obvious, i.e., “Are you wearing blue pants?,” while the other type is similar to relevant questions, such as “Where were you born?” or “Where do you live?” 


When administering polygraph tests, the examiner must be careful to follow general guidelines. Some include ensuring that the questions can be clearly understood by both the examiner and the examinee. For instance, legal and technical terms should be avoided in questioning. They may be fully understood by those working in the legal profession, but not the average person. 

The questions also cannot contain derogatory, obscene, racial or insulting phrases or words or words that can trigger an emotional response. Neither can they imply or assume guilt or ask for an opinion.  

It’s also important to avoid asking questions of a prospective employee that could violate Equal Employment Opportunity Commision rules. For example, asking about a person’s medical history before they are hired could be a violation and could subject the company to a discrimination lawsuit.



What to expect when undergoing a polygraph exam:

  • It’s voluntary, not mandatory. Because an individual who is identified as a suspect or even someone who is under arrest cannot usually be ordered to take the polygraph exam, they must volunteer to undergo the examination.
  • You will be in a relaxed position. Once seated in a quiet, private setting, the person will be asked to take a seat in a comfortable chair. Both feet must remain unmoving on the floor. Hands must remain unclosed.
  • The polygraph device will be attached in the following ways:
    • Two tubes will be comfortably attached to the person’s body. One tube will fit across the upper chest and the second will fit lower across the chest. These are used to measure the individual’s breathing patterns. 
    • A blood pressure cuff will be placed on one arm.
    • Two finger cuffs will be added to measure changes in the skin, such as perspiration.
    • Similar to the clip-like monitor used in medical settings, a plethysmograph is attached to another finger to measure blood rate volume. 
    • All of these pieces are attached to a diagnostic tool called a physiological recorder.
  • Questioning will start. The polygraph examination may require two or three hours, since questions are often asked in various ways. The entire test is composed of questions, especially questions related directly to a specific issue. For example, if you are suspected of smuggling drugs into the country on your privately owned aircraft, you might be questioned about that specifically and repeatedly, but in many different ways.  


In most instances, even the most honest person can’t completely avoid the stress of being tested. Stress affects the body in various ways, which is why the polygraph has had its share of skeptics. 

However, when lying, people do exhibit certain physical reactions, according to Dr. Bill Sullivan in an article for Psychology Today. “Knowing that dishonesty risks irrevocable damage to one’s reputation, lying is an inherently stressful activity,” Sullivan said. “When we engage in deceit, our respiratory and heart rates increase, we start to sweat, our mouth goes dry, and our voice can shake. Some of these physiological effects form the basis of the classic lie-detector (polygraph) test.”

All of those changes in the body are measurable physiological instances no one can control once they are settled in the chair, undergoing the examination. Using illegal drugs, alcohol and some prescribed medications immediately before undergoing a polygraph may cause the result to be inconclusive, meaning that neither truth or deception resulted. 



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