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

A polygraph test 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 person 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 person to a series of questions. To do that, a polygraph test evaluates a person's heart rate, breathing rate, blood pressure, and perspiration on fingertips. Sometimes, a polygraph test also evaluates involuntary arm and leg movements and nervous tics, which are often found 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 a polygraph 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 of the test. During the actual polygraph test, the examiner asks a mix of irrelevant questions, such as "What is your name?" and relevant questions, which are directly related to the issue being tested.

There is much controversy surrounding lie detector tests, as anybody can learn to cheat them with proper training and preparation. While a polygraph test is acceptable in court, many organizations are now fighting to abolish the test because it cannot be deemed one hundred percent accurate.