In a dark room with several lights glowing, there sat a tall, lanky guy. There were several wires hooked to him while two men in uniform hawked around him. ‘Did you steal the money inside the vault?’ sternly asked the taller guy in uniform. The tall, lanky guy sweated like a pig as he whimpered and said no. The other guy nodded his head as he looked at a machine scribbling lines and letters on paper.

This is how a polygraph test is usually depicted in movies and crime dramas. But this dark room scenario is far from reality. A lie detector test is done in a clean and well-lit room. The polygraph technician is seated in a table facing the machine and a computer. The apparatus is hooked on to the examinee. The examiner politely asks the questions.

As depicted in the scenes above, a polygraph is an apparatus used to record and measure vital signs such as pulse, blood pressure, skin conductivity, and respiration while the examinee is asked several questions. The patterns and differences in the responses to questions will be used to distinguish which answer is deceptive or not.

History of Polygraph

Some psychologists suggest that lying and deception is a social phenomenon and coping mechanism of some people. De Paulo, a social psychologist, defines deception as the ‘communicator’s deliberate attempt to foster a belief or understanding in others which the recipient considers to be untrue.’
Because of this, lie detection was developed to sort out the untrue from the true. Lie detection is particularly important in the justice system. Since the early years, men have explored ways on how to draw out the truth from others.
In several reports, it was found that the Chinese had a way of lie detection as early as 1000 BC. A suspected person was asked to put dry rice in his mouth. This handful of rice is later to be spitted out. If the rice is dry, it means that the person is lying. This practice was hinged on the Chinese theory that the combination of fear and anxiety causes dryness in the mouth and decreased salivation.
The Greeks also have their own way of detecting deception. Greek physician and physicist Erasistratus used the pulse to detect lies. The same technique was used in an earlier version of the polygraph created in 1921.

Other Europeans also have a method called trial by ordeal. This name alone already conjures appalling images. This involves two tests, one involving fire and the other involving water. In the fire-test, the accused was asked to carry a hot rod for a certain distance. In another variation, the accused is made to walk on embers for a certain distance. If no wounds were sustained or if the wounds healed quickly, the accused is considered innocent.

On the other hand, the water test has many variations involving water that is either cold or hot. In the hot water test, the subject is asked to place his hand inside a cauldron of boiling water for a certain period of time. If no injuries were sustained, then the accused is declared innocent. In the cold water test, the subject is thrown into a body of water inside a sack. If the accused is able to escape, he is off the hook.

These tests are conducted based on God’s justice system. They believed that God will not let the innocent suffer and the unjust prevail.
The modern polygraph machine was first developed by an anthropologist, physician, and criminologist from Italy, Cesare Lombrosso. The machine was called Lombrosso’s Glove. The machine monitored and recorded the how the blood pressure increased and decreased as the subject answered questions.
William M. Martson greatly improved on the technology during the first World War. Several years after, Leonard Klee and John Larson were able to design and develop a device called the ‘Cardio-Pneumo Psychograph,’ or more popularly, the polygraph. The earlier versions of the lie detector test measured the skin’s bioelectric reactivity or skin response, blood pressure changes, and respiratory rate.

As of today, the polygraph is widely used throughout the world especially in the field of justice. In the United States, the admission of the results of a lie detector test is left to the jurisdiction of the lower courts.

Polygraph Questions and Tests

There are various question types asked during a polygraph tests. These questions include control questions, relevant questions, irrelevant questions and confidential information questions. The examiner mixes up questions of different types to legally illicit the truth from the accused.
Control questions are general those that pertain to the topic of the inquiry. Relevant questions are those that directly attack the topic of inquiry, while irrelevant questions are those that are intended to make the examinees warm up towards the examiners. Confidential information questions are only asked on special cases.

There are also different kinds of tests such as Comparison Question (Control Question) test, Concealed Information Test, Peak-of-Tension Test, Stimulation Test and many more. The examiner must correctly and wisely question the examinee to get the right answers and accurate readings.
Polygraph tests are credible and based on sound scientific theories. According to Raymond Nelson of the American Polygraph Association, although it is more popularly known as a lie detector test, it does not really test lies per se. More appropriately, its results indicate the probability that the person is telling the truth.