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A Brief Overview of Lie Detection Methods

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Wouldn’t you love it If you could detect the difference between lying and lying? However, most conventional methods of detecting lies, such as polygraph machines are no better than pure chance. While polygraph machines aren’t accurate in determining if a person is deceiving They can monitor the cardiovascular, respiratory and electrodermal activity very precisely!

A Short Overview of Lie Detection Techniques

One of the first methods of lie detection was hypnosis. It has been employed in a formal capacity from the 1840s. It was regarded as a form of sleep that is artificially produced experts believed that people who were hypnotized would be more honest in this vulnerable (and possible) state. In addition to the questionable ethicality of this procedure however, the results were not reliable.

In the early 1900s in the 1910s, a doctor who administered Scopolamine (or “twilight sleeping”) on patients observed they were compelled to disclose personal details. This led to the development of a field known as narcoanalysis. In the use of barbiturates, such as sodium pentothal and sodium amytal were administered to those who were being interrogated in the form of “truth serum”. The theory behind this method was that psychoactives lowered the person’s defenses, which makes people more likely speak truthfully. Certain forms of narcoanalysis are used today, however not in the majority of well-established democratic societies.

The history of Lie Detector Test

In 1921 the year 1921, the 1921 California police officer called John A. Larson developed an instrument which could simultaneously track changes in heart rate, blood pressure and respiration. This device was dubbed the polygraph, or more casually called”the lie detector. The operation of the device could be traced back to two prior advancements:

The year 1914 was the time that Italian psychotherapist Vittorio Benussi wrote Die Atmungssymptome der Lüge which was his study of the effect of lying on respiration function
It was 1915 when American psychotherapist William M. Marston created a continuous systolic blood pressure test to identify deceit

Larson used his devices and methods on actual cases within his own precinct. However, his aide, Leonarde Keeler, refined the procedures for testing and made the device more portable and also included an element that could measure the galvanic skin reaction of the patient.

The Trial of Lie Detectors

The year 1923 was the first time William M. Marston tried to get the results of the lie detector test accepted as evidence before the court of law. This would later be known as the case of historical significance United States v. Frye. The court denied the results of the lie detector and established the Frye standardthat will set the standard for admissibility of experts’ evidence on the part of U.S. courts for years to be.

Over 40 times later, back in the year 1965 in 1965, in 1965, the United States Committee on Government Operations conducted the first scientific study of the polygraph device, concluding that it was unreliable in detecting deceit as it was scathingly stated in the opening paragraph of this article. However, at this point those who supported this test were still going in full force, not frightened by the committee’s findings.

A different notable change occurred in 1983, as U.S. president Ronald Reagan issued the National Security Decision Directive 84 which allowed federal agencies to employ polygraphs in their work. In a surprising (and embarrassing) revision the president revoked the directive three months later due to an adverse evaluation of the method conducted from Office of Technology Assessment. Office of Technology Assessment.

The Essential Science Behind Polygraph Tests

Polygraph tests monitor three bodily responses that are commonly connected to deceit:

Cardiovascular activity
Respiratory activity
Electrodermal activity

Cardiovascular Activity

Blood pressure, heart rate and other cardiovascular functions are affected by actions often associated with lying like responding to the threat of a perceived or anticipated (“fight or fight or” action) and an increase in mental activity. Polygraphs are used to measure the cardiovascular activity of an arm, wrist or finger cuff fitted with a sphygmomanometer. It is similar to the ones used in medical facilities.

Another method of measuring cardiovascular health is photoelectric plethysmographs. These are attached to the patient’s finger or ear to send infrared light into the tissue. Photosensors measure light which is reflected, or passes across the tissues. This directly relates to the volume of blood that it traveled before arriving at the sensor. This permits the physician to observe changes in blood volume without having to use an instrument to measure pressure.

Respiratory Activity

Changes in the respiratory activity of the body can also be a sign of deceit however, since breathing can be controlled by your central nervous system the test is considered to be less reliable.

The activity of the lungs is measured by attaching pneumatic rubber bellows to the abdomen and thorax of the subject. Inhalation and exhalation both expand the bellows, causing shifts in the thoracic as well as abdominal circumference. The changes in internal pressure are measured using an instrument for measuring pressure.

Electrodermal Activity

Electrormal activity measurement is believed to be the most reliable and sensitive of the three tests. Why? Skin’s resistance to electrical current as well as conductance are mostly determined by the eccirine glands which are responsible for generating sweat. They are control by the sympathetic nervous system.

Electrodermal activity is monitored using two electrodes that are attached to the palm or fingers of the subject. A small amount of current is applied to the skin, which determines the conductance of the skin, as well as any changes in it in addition to its frequency, the intensity of the spontaneous reactions and the amplitude of event-related responses and many other variables.

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Deteiving Fraud, Deceiving Results

The polygraph monitors its subjects’ physiological responses in real-time by using the use of a line graph that contains three values which correspond to the respiratory, cardiovascular and electrodermal outcomes. But, how do you know if the results of the physiological tests are applicable to the psychological issue as to whether the individual is lying? It is an open question.

One of the major problems with the accuracy of polygraph tests is that the physiological response to the test could vary significantly between people -or even within the same person in different conditions. Furthermore, breathing patterns could affect the rate of their heart and their the galvanic skin reaction. The people who practice breathing and mindfulness techniques may have some control over the physiological reactions (typically to control stress however they may be as deceiving as is possible! ).

If polygraph tests are not reliable, what alternatives can be used to detect deceit? Criminal justice and law enforcement professionals frequently employ advanced interrogation methods, where the polygraph is utilized to provide a psychological benefit to the interrogator and not as a real, tried-and-true snare of deceit. Advanced interrogators are even trained in facial microexpressions as well as non-verbal signals. Although these techniques aren’t easy to quantify, investigators’ instincts are more trustworthy as compared to “chance”.

The development of better physiological testing devices

Certain blood pressure monitoring devices aren’t used just to detect if people are lying. They are actually an vital to medical science as blood pressure is generally measured each when we visit an office of a doctor.

Certain blood pressure monitoring devices function by using piezoresistive pressure sensors. This is an MEMS device which utilizes the effect of piezoresistive, which is when the resistance to electrical current changes when the application of force to the semiconductor.

When developing the device to monitor blood pressure it is crucial that the piezoresistive sensor can accurately measure the blood pressure of the patient in a manner that is safe to the individual. It is therefore crucial that the designers can describe the workings and operation of the devices. They can also anticipate their behaviour, and evaluate their performance prior to when they’re released to the market.