What Is a Polygraph Test? - History, Reliability & Accuracy

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  • 0:03 History
  • 0:56 Reliability
  • 1:47 Accuracy
  • 2:31 Lesson Summary
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Lesson Transcript
Instructor: Jessica Schubert

Jessica is a practicing attorney and has taught law and has a J.D. and LL.M.

In this lesson, you'll learn what a polygraph test is and go over a brief history of the polygraph test. You'll also briefly review the reliability of the test and discover how accurate it is determined to be by the courts.


Have you ever told a little white lie and gotten away with it? Well, the lie detector test, or the polygraph, might call your bluff.

In the 1920s, California psychiatrist John Larson created a contraption that measured one's pulse, respiration, and blood pressure. This contraption was used with the Berkeley Police Department in connection with numerous criminal investigations and was able to assist in the identification of criminals and innocent people. Many consider Dr. Larson's creation to be the first polygraph machine.

However, in the 1930s, a psychologist known as Leonard Keeler created another device which also included the measurement of the skin reactivity to electronic stimulus, referred to as galvanic skin response. Keeler patented this device. Keeler later gained the reputation as the father of the modern day polygraph machine.


Polygraph machines are considered reliable for law enforcement purposes by some agencies. For example, police officers use polygraphs with witnesses in trying to determine whether a person may have committed a crime. Conversely, the polygraph machine can help determine if someone is innocent. Polygraph tests are also used in private industry. For example, some companies will utilize polygraph tests in order to assess candidates in the interview process in high security clearance positions.

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