A normal person's conscious mental effort to deceive causes involuntary physiological changes which are the body's reaction to an impending threat to its well-being. These inner deviations are beyond control and are triggered by the stimulating effect of well-prepared questions to which truthful responses may result in punishment.
This phenomenon can be explained thus: our bodies adapt to their environments as efficiently as possible. Any change can cause our bodies to automatically adjust in order to survive. Otherwise, we will quickly perish. Our complex system of internal checks and balances, which primarily involves the body's autonomic nervous system, is responsible for this ability to adjust.
All relevant physiological activities are measured and recorded when a person is examined under the polygraph. A physiological chain reaction occurs when stimulus is perceived by the subject to be threatening to his person. The subject's body adjusts automatically and his fight or flight mechanism kicks in to protect him from the consequences of being caught in a lie.
Such changes in the human physiology are detected and recorded by the polygraph machine and the trained lie detector examiner can read these recordings to detect possible deception. Once again, it is well to emphasize that the "lie detector" does not detect lies. Rather, it measures certain identifiable physical reactions, such as those affecting respiration, pulse, and galvanic skin resistance, and is useful when combined with a reliable questioning technique.
Lying is a type of deception that involves deceiving others verbally. It's a natural part of how we communicate with other people. It's a recurring aspect of human social behavior.
Humans cannot really have an idea as to how many lies they've told. It happens in daily life, especially with people who are afraid of others finding out the truth about them. Many lie to their parents, partners, friends, supervisors and practically everyone else with whom they would interact.
People lie for a variety of reasons. Sometimes, it is done to shield oneself against problems, while at other times it is to get away from responsibilities. People would also consider the potential for embarrassment or threat if a truth is revealed. As a result, people come up with a solution in the form of lies. Albeit, it is a clumsy approach to problem-solving.
According to a study done on self-reported frequency of lying, people lie in about 25% of their interactions with others during their normal daily activities. These lies only differ in their severity, frequency, target, and the reasoning behind the lies.
Lying can take two forms: short-term lying, which requires little planning, and long-term lying, which requires a lot of planning.
Because people lie for a whole variety of reasons, the psychology of lying can be difficult to grasp. The causes of the lying behavior can also be described in a variety of ways. Over time, the reasons for lying also change. Children tend to lie for fun or to avoid punishment from parents or other authority figures. As people grow older, they discover that lying has a survival value. In other words, people lie to protect themselves from a perceive threat to their survival or well-being. People lie and hide the truth to keep themselves safe.
The following are a couple of theories that have been used to explain lying:
Sigmund Freud's psychoanalytic theory purports that the mind is made up of the id, ego, and super-ego. Our actions are said to be the result of the interplay between these three different parts of our mind. The ego is the mental level that operates according to the reality principle. The id sometimes sometimes forces people to stay away from reality because it is causing anxiety.
Maslow's hierarchy of needs states that we have an innate desire to meet our needs one by one. In order to achieve higher levels in this hierarchy and avoid stumbling blocks on the way to meeting one's needs, people could make statements that may not be true.
Neuropsychologists have noticed a marked difference in brain activity when a person tells the truth and when a person tells a lie. Because different parts of the brain are used to deliberately tell a lie than they are to speak the truth, there is a clear distinction between the two from a neuropsychological standpoint.
There are also mental disorders that could cause a person to tell lies without realizing that what they are saying is not true. These include the paranoid personality disorder and some of the dissociative disorders.
Despite the fact that most people aren't very good at detecting lies, scientific research has uncovered a few noteworthy methods for detecting deception. The use of physiological measures such as the polygraph to detect evidence of deception is just one of them.
Is polygraph result/examination admissible as evidence in court? The answer is rather complicated.
The answer could be "YES" if allowed by the judge. However, if the test was administered by an unqualified and inexperienced examiner, the results are unlikely to be used by the judges.
Today, there is a lot of activity in the court system regarding the use of polygraphs and the laws are rapidly changing.
Under the following conditions, polygraph and expert testimony relating to it may be admissible with a stipulation to support other evidence of a defendant's involvement in a crime or to support or charge his testimony:
That the admissibility of the polygraph test is a matter for the trial judge to decide. The trial judge may reject such evidence if he is not convinced that the examiner is competent or that the result was not obtained under proper conditions;
That both parties' counsel and the subject sign a written condition for the subject's admission to the examination and subsequent admission to further polygraph tests and examiner's opinion on behalf of either the defendant or the state;
If the examiner's opinion is offered as evidence, the opposing party is entitled to cross-examine the examiner on the following topics:
The qualifications and training of the examiner;
The stipulation under which the test was administered;
The restrictions and possibilities for the errors of the technique;
At the good judgment of the trial judge, any other matter deemed important to the inquiry.
Studies on the accuracy of the polygraph test have been conducted over the last 75 years. It is difficult to draw a precise figure for the accuracy of polygraph testing in all settings from the data because many different factors are involved and the test itself is a very complex process. Nonetheless, the overwhelming body of evidence suggests that when a properly trained examiner employs a well-established testing procedure, the accuracy of the polygraph examiner's decisions is generally in the range of 95%-100%, depending on the factors influencing the test.