With detective shows and original investigation clips on the social media platforms, many of us have come across the term- “Lie Detection Test”. So, what is a lie detection test and when, where and how do one use it? As the name suggests, the main objective of “Lie Detection Test” is to determine if a person is answering certain questions truthfully or not. They are often termed as “Polygraph Tests” as well. During the test, the concerned person has four to six sensors attached to him. The polygraph machine records signals through the sensor in the form of a graph. It is often used for during police investigations and even during an interview for job with FBI & CIA.
How does it work? Worry not, because we are here to help you with it. Let us break it down for you and tell you the truth about lie detectors. Here are the answers to some commonly asked questions on how a lie detector works?
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What does the sensor record to form the graph?
Usually there are four to six sensors that are attached to a person while they take a lie detection test. The four major changes and movement the sensors record are:
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The pulse rate
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The breathing rate
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The rise or fall of blood pressure
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The rate of perspiration
At times, even hand and leg movements get recorded in the polygraph test.
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How does the lie detection process work?
Once the person is connected to the recording device, a questioner will ask the concerned person a set of questions. The procedure is often termed as “stimulation test”. This test is the demonstration of accuracy of the polygraph machine. Also there are different techniques which are used for questioning the concerned person. Here are the two popular questioning techniques of a polygraph test.
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CQT or Control Question Technique:
CQT is the most widely used method of questioning during a lie detection test. The questioner has a clear and prior knowledge of the examinee’s past cases and reports. Before the polygraph test is conducted, the examinee gets to talk about their end of the story or put forward their point of view. During the polygraph test, the examiner asks questions based on the prior conversation with the examinee. The answers to the questions are restricted to “yes” or “no”. The three general types of questions are:
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Relevant Questions: where the examiner asks questions that are directly related to the crime.
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Control Questions: where questions are about more similar sort of misconducts and issues that are similar to the investigation.
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Irrelevant questions: where questions asked are completely focused on neutral issues but those that are related to the subject.
Fear of control questions is said to impact more for a person who is telling the truth. This is because relevant questions are directly connected to the crime they did not commit. In case of control questions, the questions arouse concerns about how truthful they were about their past.
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GKT or Guilty Knowledge Test:
Another popularly used technique for a polygraph test is GKT. GKT is not as widely used as CQT. It’s a technique where questioner will ask the examinee few sets of questions and give him multiple choices to choose from. Amongst the options for the answers, only one answer is directly related to the question asked and the rest are neutral. A person who is innocent will never be able to figure out the difference between the choices that are give. In case of the person who is guilty, he will exactly be able to figure out the most relevant options amongst all. The test will determine lie or truth based on the response of the examinee as well as the changes of the physiological functions.
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How does a polygraph test help?
Lie detection tests have always been a controversial topic. Many believe that a lie detection test cannot give guarantee of the accuracy of the results. However, most scientist and psychologists believe that these tests do have validity. They believe that it needs a lot of effort to deceive a powerful machine such as polygraph. Polygraph officials are also highly trained and hence very difficult to deceive.
