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Basics of Lie Detection

Basics of Lie Detection

For those of us who aren’t familiar with the device through movies, lie detectors may sound like a miracle machine that points out if a person is a cheater or not. In reality, the lie detector is nothing but a device that records several medical readings of the body.

When we tell lies, several of our physiological behavior changes, like the heartbeat, breathing etc. In light of this fact, polygraphs or lie detectors were designed to determine if the regular readings of the body are changing or not.

What a polygraph reads

A polygraph reads the measurement of a subjects’ blood pressure, heart rate, respiratory rate and electrodermal activity. Some polygraphs can also record body movements. In general, changes or fluctuations in these readings shows that a subject is telling by lie detector. The final result is however determined by the examiner.

What Polygraph exams are used for

Polygraphs are most often used for investigations related to murder and theft. However, this has changed now and polygraph examinations are being undertaken by the public too. These exams can be used to resolve domestic fidelity issues or company cases. Sometimes job interviews necessitate polygraph exams as well.

What questions are asked

Each case has an entire procedure to it. First pretests involve an interview with the examiner who is a qualified polygrapher. Next, the questions are formulated on a ratio of 4 to 10, i.e. if there are 10 questions, only 4 are directly related to the issue while others are general. General questions are asked in order to get the normal readings of a subject.

The answers to the vital questions and the body response is then measured against the normal readings of the body to determine truth from lies.

Final verdict

The final result is only determined by a practitioner or a group of practitioners who analyze the data thoroughly to rule out false positives or false negatives. Due to the vulnerability of the readings, polygraph tests are not viable in courts. However, they have successfully been used for investigations and private works for a long time.


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