Interesting Facts About the Polygraph: Part 1
1. The Invention of the Lie Detector
The first device for detecting lies was called the “hydrosphygmometer” (or hydrosphygmograph: “hydro” because the subject’s hand was placed in a tub of water). It was used by Italian criminologist Cesare Lombroso. In the 1890s, Lombroso measured the blood pressure of suspects while they were being interrogated by the police. He claimed he could determine when criminals were lying. By showing suspects photos related or unrelated to the crime, he simultaneously recorded their pulse rate.
Max Wertheimer, a German researcher at Prague University, was the first to combine devices and the method of word associations in 1904, using physiological responses to questions. He used a plethysmograph, hydrosphygmograph, numograph, and pneumograph to measure breathing rate, heart activity, and electrodermal activity.
In 1908, German psychologist Hugo Münsterberg applied various instruments to record and analyze physiological reactions. Münsterberg wanted to use his method in criminal law. During investigations, suspects were asked questions about crime details known only to the police and (presumably) the perpetrator. Questions with possible answers were asked in turn, and physiological signals were recorded. Possible answers included the correct one and several plausible but incorrect alternatives (e.g., “Was the victim killed with (a) a gun, (b) a knife, (c) a rope, (d) a bat, (e) an ice pick?”). For an innocent suspect, all alternatives seem equally plausible, but for the guilty, the correct answer triggers a stronger physiological response.
Münsterberg’s method became the basis for the modern Concealed Information Test (CIT), used as an alternative to the more common Control Question Test (CQT), where the subject answers “Yes” or “No”.
Dr. William Marston measures a subject’s pulse, 1922. Marston was not only a talented psychologist studying lie detection, but also a comic book artist, feminist theorist, and amateur BDSM practitioner. He created the now-famous character Wonder Woman, inspired by his wife Elizabeth Marston and Olive Byrne, who lived with them in a polyamorous relationship.
In 1915, Münsterberg’s student Dr. William Marston discovered that changes in systolic blood pressure were linked to lying, and in 1917 he applied his discovery in the military to detect enemy spies. He published his results in the classic 1921 article “Physiological Possibilities of the Deception Test”.
2. The First Modern Polygraphs
Researchers gradually came to the idea of using a single universal device that could record several indicators at once—a polygraph in the modern sense. The prototype of the modern lie detector was developed in the 1920s by John Larson, a California police officer. After studying Marston’s work, Larson decided he could improve the method. He began testing subjects with a “cardiopneumopsychogram,” a forerunner of modern polygraph charts.
His device allowed simultaneous recording of blood pressure, pulse, and respiration. Larson was the first to use more than one channel at a time to detect lies. He conducted many tests on criminal suspects with this device.
Larson called his instrument a “polygraph,” borrowing the term from John Hawkins, who coined it in 1804 for a machine that made accurate copies of handwritten texts.
In the 19th century, a polygraph was a device for copying handwritten text.
The name “polygraph” comes from two Greek words—”poly” (many) and “grapho” (to write). This device was used in the 19th century by many, including Thomas Jefferson, the third U.S. president and author of the Declaration of Independence.
However, John Larson was the first to apply the word “polygraph” to a device for detecting lies. He also developed the first portable polygraph, using it regularly in the field. He conducted many polygraph tests from 1921 to 1925. His device is now in the Smithsonian Institution in Washington, D.C.
3. Leonard Keeler’s “Emotographs”
In 1924, John Larson’s student and colleague Leonard Keeler created his own detector, which he called the “Emotograph.” In 1926, he added an extra channel to the polygraph to record changes in skin resistance, greatly improving test accuracy.
Keeler’s polygraph, created in 1933, was used in the Chicago Crime Detection Laboratory. By 1935, he had tested about 2,000 criminal suspects.
Leonard Keeler using one of the first polygraphs, 1920s.
Later, Keeler introduced a fifth channel to record muscle tremor. This marked the beginning of the modern era of “lie detection.” The basic set of channels (breathing, blood pressure, skin resistance, and tremor), proposed by Larson and Keeler, is present in all modern devices.
4. How Does a Modern Polygraph Work?
A modern polygraph records signals from sensors attached to various parts of the body. Changes in these indicators are associated with fluctuations in arousal levels. It is believed that lying causes a higher level of arousal than telling the truth. This may result from feelings of guilt or, more likely in the context of polygraph testing, fear of being caught lying.
The “Keeler Model 302c” polygraph, which recorded breathing rate, cardiac activity, and galvanic skin response, was used by the FBI in the 1950s and cost $450.
Today, polygraphs can very accurately record changes in palm sweating, blood pressure, and breathing, being sensitive even to the slightest shifts. Pneumatic tubes are placed on the chest and abdomen to record changes in breathing depth and frequency. Blood pressure changes are recorded with a special cuff around the arm, and palm sweating is measured with metal electrodes attached to the fingers. In some cases, brain electrical activity (evoked potentials) is also recorded.
Modern lie detectors can record up to 50 physiological parameters: facial flushing, lip trembling, pupil dilation/constriction, increased blinking, and other changes that may indicate lying. For example, devices can detect changes in capillary dilation—a simple reflex response known as “blushing” or the “color of embarrassment,” which is a reaction to a shocking question. This response cannot be controlled by willpower as easily as breathing can.
Some polygraph models can analyze human speech (voice spectrograms). It is believed that when a suspect knowingly lies, the state of their vocal cords changes, producing a slightly distorted sound due to irregular changes in the fundamental frequency of vibration.
Other detectors respond to temperature changes around the eyes. The principle is that when a person experiences psychological discomfort—lying or being evasive—intraocular pressure increases, blood rushes to the eyeballs, and the temperature around the eyes rises.
In Stanley Kubrick’s famous film “A Clockwork Orange” (1971), a supposedly reformed criminal is forced to watch scenes of violence while sensors analyze his true reactions.
In recent years, new lie detection technologies have been developed, using psychosemantics (analyzing the subject’s semantic fields), psycho-probing (analyzing subconscious reactions to subliminal test stimuli), and magnetic resonance imaging (analyzing neural activity in specific brain regions). There is no doubt that even more sophisticated methods will appear in the near future.
5. Which Is Correct: Polygraph or Lie Detector?
The polygraph is often called a lie detector, but this term is not entirely accurate and can be misleading. The polygraph does not read minds or detect lies; it only records physiological activity and changes in its parameters. It detects not lies, but arousal, which may indicate lying with a certain probability. Physiological reactions cannot precisely determine the psychological process that caused them (positive or negative emotion, lie, fear, pain, associations, etc.).
Currently, there is no other way to detect lies except indirectly, since there is no 100% reliable physiological pattern unique to lying. There are no unique physiological laws directly and unambiguously linked to lying.
Therefore, the terms “polygraph” and “lie detector” are not synonyms. Technically, “polygraph” refers only to the device used to record various physiological parameters. “Lie detector” is a more colloquial term, popular outside professional circles, especially in journalism and pop culture. In reality, there is no true “lie detector” today.
6. Is Lie Detection a Science? Research on Polygraph Effectiveness
Contrary to popular belief, polygraph testing is not a strictly scientific or standardized procedure. There are many doubts and critical remarks about the scientific validity of the results. It is considered more of an art than a science, as much depends on the polygraph examiner’s qualifications, experience, and intuition.
Unlike scientific, strictly standardized tests and experiments, the list of questions for a polygraph test is not fixed. For successful testing, the examiner must select and formulate questions to provoke the desired reaction in the specific subject, and then correctly interpret the wide variety of physiological manifestations, which differ greatly among individuals. This inevitably leads to errors caused by the so-called “human factor.”
Because of this, many critics call polygraphy a “pseudoscience,” and blind faith in it can lead to unfortunate consequences.
In 1986, after a high-profile spy scandal, the UK government announced plans to conduct pilot studies on the effectiveness of polygraph testing. A group of well-known psychologists, led by Professor M.A. Gale, was tasked with reporting on the effectiveness of polygraph testing.
The final report, “The Polygraph Test: Lies, Truth and Science,” was published in 1988 by the British Psychological Society’s Working Group on the Use of the Polygraph. It contained sensational results that shocked many. Psychologists questioned almost every aspect of the polygraph, especially the accuracy of results and its role in personnel screening, investigations, and suspect interrogations. They stated that the procedures are not standardized enough to be considered satisfactory in terms of scientific psychometrics.
Polygraph testing is not a strictly scientific procedure, as results cannot be standardized or objectively verified. Different specialists may interpret the data in completely different ways.
Another “Report of the Working Group on the Use of the Polygraph in Criminal Investigation and Personnel Screening,” published in 1986, also found difficulties in verifying the methodology and practice of testing by different polygraph specialists. It stated, “Procedures used in polygraph examinations are not standardized, and there is no simple method for checking the work of individual polygraph examiners in practice.” This means the decision-making process is subjective, depending entirely on the examiner conducting the test, and is not verifiable. Other specialists may find it difficult to understand why a particular examiner reached a certain conclusion.
The report concluded that polygraphs can be fooled, and innocent people can be found guilty. The commission also decided that some aspects of polygraph testing, especially misleading the subject during the Control Question Test, conflict with British law and moral standards, making the results inadmissible in British courts. The UK government abandoned plans to introduce polygraph testing.
In 2002, the U.S. National Research Council conducted a major study, “The Polygraph and Lie Detection.” It stated:
“Polygraph research has not developed over time into a scientific discipline. No body of knowledge has accumulated that could significantly strengthen its scientific basis. This lack of progress can at least partly be explained by the use of the polygraph almost exclusively by practitioners with little connection to academia. Historically, the CQT (Control Question Test) was developed mainly outside academic science. Operators conducting tests are most often law enforcement officers without academic training in psychology, physiology, or psychophysiology…”
“Although the probability of detecting lies with a polygraph is much higher than random guessing, testing produces too many errors and false positives. The federal government should not rely on the polygraph for screening current or potential employees, for detecting spies, or for other national security threats, because the test results are too inaccurate for such use,” the report states.