What is a Polygraph Test?

A polygraph test evaluates a person's physical responses to a series of questions.
The perspiration on a person's fingertips is evaluated during a polygraph test.
A person may be asked to take a polygraph test in order to determine whether he or she has cheated on a significant other.
Article Details
  • Written By: Diana Bocco
  • Edited By: Bronwyn Harris
  • Last Modified Date: 22 November 2015
  • Copyright Protected:
    Conjecture Corporation
  • Print this Article
Free Widgets for your Site/Blog
Finland and North Korea are separated by a single country: Russia.  more...

November 28 ,  1943 :  The key leaders of the Allied forces during World War II met for the first time in Tehran, Iran.  more...

Also known as a "lie detector test," a polygraph test is not something out of the movies. Polygraphs are a common part of criminal investigations and background checks. More and more companies, especially government bodies, now require these tests from potential employees.

A polygraph is a simple machine that consists of six sensors or "wires" that are attached to the person taking the test. The examiner, known as forensic psychophysiologist (FP), observes a sheet of moving paper and the type of lines drawn on it by a special pen. These lines vary according to the emotional reaction of the subject to the questions, and these signals are recorded on paper.

Despite what the name suggests, a polygraph test does not detect lies, but rather evaluates the physical responses of a subject to a series of questions. To do that, it evaluates the subject's heart rate, breathing rate, blood pressure, and the perspiration on his fingertips. Sometimes, a polygraph also evaluates involuntary arm and leg movements and nervous tics, which are often detected during difficult questions. Generally, when a person lies, his or her heart rate increases, he starts sweating, and his whole body reacts. This is what the test measures.


Before a polygraph test starts, the examiner and the person taking the test will go through a "pretest interview." During this time, the examiner will explain how the test works and review the questions to be asked. In the case of legal issues, a lawyer is usually present during this phase. During the actual test, the examiner asks a mix of irrelevant questions, such as "What is your name?", and questions that are directly related to the issue being tested.

There is a good deal of controversy surrounding lie detector tests, as anybody can learn to cheat them with the proper training and preparation. While the results of a polygraph test can be used in court, many organizations are now fighting to abolish the practice because it cannot be 100% accurate.


You might also Like


Discuss this Article

Post 3

A polygraph is not acceptable in court, since it does not provide sufficient proof of anything but physical responses.

Post 2

@ GenevaMech- You brought up an interesting fact about white coat syndrome, and for this very fact, I believe that polygraph lie detector tests should be inadmissible in court. I would assume that being subject to a lie detector test is a nerve wracking experience, and quite a few people show symptoms similar to white coat syndrome when they are nervous. Peoples blood pressure can fluctuate by as much as thirty points from nervousness, so I wouldn't be surprised if these tests have falsely convicted people in the past.

Post 1

I almost think it would be fun to take a polygraph test just for accuracy's sake. I would probably do horribly, since I get white coat syndrome (blood pressure rises when a doctor walks in the room, but subsides when I calm down), but I would be curious as to how accurate they are. You always see that CIA operatives and other intelligence agents are trained to beat them in movies.

Post your comments

Post Anonymously


forgot password?