Polygraph in World War I: Military Deception Detection 1914–1918

The State of Physiological Research Before 1914

When war erupted across Europe in August 1914, the scientific study of deception was still confined almost entirely to university laboratories and academic journals. The idea that lying produces measurable physiological changes had roots stretching back to ancient civilizations, but the systematic, instrument-based approach to detecting deception was barely two decades old.

The most significant pre-war contributions came from Italian criminologist Cesare Lombroso, who in 1895 published an account of experiments he had conducted on criminal suspects using a modified hydrosphygmograph to measure blood pressure and pulse changes during police interrogation Verified History of Polygraph — Ohio Polygraph Services
Confirms Angelo Mosso was the first scientist to report that breathing patterns change under certain stimuli, causing variations in blood pressure and pulse rate. Mosso's work established the fundamental principle underlying all subsequent polygraph development: that psychological states produce measurable physiological changes Verified History of Polygraph — Ohio Polygraph Services
Confirms Angelo Mosso was the first scientist to report that breathing patterns change under certain stimuli, causing variations in blood pressure and pulse rate. To learn more about his family's contribution, see our profile of Domenico Mosso and the plethysmograph legacy.

In the German-speaking world, Hans Gross, the Austrian jurist and criminologist, had been advocating for scientific methods in criminal investigation since the 1890s. His landmark textbook on criminal investigation discussed the observable signs of deception, including changes in breathing, facial colouring, and nervous movements. While Gross did not develop instruments for measuring these changes, his systematic approach to observation created an intellectual framework for forensic deception detection.

Meanwhile, Carl Jung's word association test, developed in the early 1900s at the Burghölzli clinic in Zurich, demonstrated that response time delays and physiological changes during word association tasks could reveal hidden emotional conflicts [5]Verified Word Association Test in Jungian Psychology
Confirms Jung modified the word association test for forensic investigation and published cases of successful criminal detection. Jung modified the test for forensic investigation and published remarkable cases of successful criminal detection [5]Verified Word Association Test in Jungian Psychology
Confirms Jung modified the word association test for forensic investigation and published cases of successful criminal detection. His work showed that words associated with guilty knowledge produced measurably different responses than neutral words — a finding with obvious implications for interrogation.

The Intellectual Climate of 1914

By 1914, several key principles had been established in the scientific literature. First, deception produces autonomic nervous system arousal. Second, this arousal manifests in measurable physiological changes including blood pressure fluctuations, respiratory pattern alterations, and galvanic skin response changes. Third, instruments could be designed to record these changes. Fourth, the specific pattern of changes could potentially differentiate truthful from deceptive responses.

What was missing was any practical system for applying these principles outside the controlled conditions of a university laboratory. The instruments were large, delicate, required careful calibration, and depended on quiet, controlled environments. The testing protocols were informal and unstandardised. The interpretation of results was subjective and highly dependent on the skill and experience of the individual researcher. And critically, no one had yet developed a systematic questioning technique designed specifically for deception detection — a gap that would not be filled until the development of the Relevant-Irrelevant Test in the 1920s.

It was into this landscape of promising but immature science that the demands of the Great War would inject an urgent need for practical application. The largest conflict in human history would create unprecedented intelligence requirements that pushed researchers to consider how their laboratory work might serve the needs of military interrogators.

The Scale of the Intelligence Problem

World War I was the first conflict in which intelligence gathering became a truly industrialised operation. More than 65 million soldiers were mobilised across the belligerent nations, espionage networks operated on an unprecedented scale, and the static nature of trench warfare on the Western Front created a constant need for tactical intelligence about enemy positions, plans, and strength.

The traditional methods of military interrogation were proving inadequate for the scale and complexity of the task. Before WWI, interrogation of prisoners of war relied primarily on direct questioning, the exploitation of captured documents, and the assessment of prisoner credibility based on the interrogator's experience and intuition. These methods were inconsistent, time-consuming, and easily defeated by trained or motivated subjects.

During WWI, approximately 10 million people — servicemen and civilians — were captured and sent to prisoner-of-war and internment camps [6]Verified Prisoners of the First World War — ICRC Archives
Confirms approximately 10 million people were captured during WWI and sent to prisoner-of-war and internment camps. The sheer volume of prisoners, particularly after major offensives, overwhelmed the limited number of skilled interrogators available. The American Expeditionary Forces (AEF) alone held nearly 48,000 prisoners of war by the time of the Armistice on 11 November 1918 [7]Verified WWI Prisoners of War Become Valuable Intel Sources
Confirms the U.S. held nearly 48,000 POWs by the Armistice and details Major Nolan's hierarchical interrogation system. AEF G-2 intelligence chief Major Dennis Nolan developed a hierarchical system for examining prisoners at all echelons, publishing guidelines in the Army's first Combat Intelligence Manual in 1918 [7]Verified WWI Prisoners of War Become Valuable Intel Sources
Confirms the U.S. held nearly 48,000 POWs by the Armistice and details Major Nolan's hierarchical interrogation system.

AEF interrogators found that simple and direct questioning, combined with courtesy, was the most effective method for eliciting information [7]Verified WWI Prisoners of War Become Valuable Intel Sources
Confirms the U.S. held nearly 48,000 POWs by the Armistice and details Major Nolan's hierarchical interrogation system. Noncommissioned officers were considered the best sources, while about 60 percent of officers refused to cooperate, invoking military honour [7]Verified WWI Prisoners of War Become Valuable Intel Sources
Confirms the U.S. held nearly 48,000 POWs by the Armistice and details Major Nolan's hierarchical interrogation system. The most valuable intelligence obtained from prisoners was enemy order of battle, but they also provided details on trench positions, routes of movement, and morale [7]Verified WWI Prisoners of War Become Valuable Intel Sources
Confirms the U.S. held nearly 48,000 POWs by the Armistice and details Major Nolan's hierarchical interrogation system.

Espionage and Counterintelligence: The Invisible War

Beyond prisoner interrogation, the war created a massive counterintelligence challenge. Both sides operated extensive spy networks in enemy territory and neutral countries. The execution of Mata Hari, the discovery of the Zimmermann Telegram, and the constant fear of sabotage in munitions factories all highlighted the critical importance — and difficulty — of identifying deceptive individuals.

British intelligence, operating through MI5 (domestic) and MI6 (foreign), processed thousands of suspected spies and informants during the war [8]Verified WWI Primary Resource Guide: Prisoners and Spies
Confirms the National Archives hold over 150 top-secret MI5 files from WWI concerning espionage and surveillance. The National Archives hold over 150 top-secret MI5 files from this period, containing interrogation reports, surveillance details, and intelligence on individuals and organisations under suspicion [8]Verified WWI Primary Resource Guide: Prisoners and Spies
Confirms the National Archives hold over 150 top-secret MI5 files from WWI concerning espionage and surveillance. The interrogation of suspects was a labour-intensive process that relied heavily on the personal judgment of experienced officers. There was no scientific method available to distinguish between a genuine double agent, a fabricating informant, and a truthful source.

American military intelligence, entering the war in 1917, was particularly ill-equipped for these challenges. The U.S. had a minimal intelligence apparatus when it declared war on Germany, and had to rapidly build an interrogation and counterintelligence capability largely from scratch. This institutional void created an opportunity for innovative approaches, including the potential application of scientific deception detection methods being developed in American universities. The wartime intelligence programmes established during WWI would evolve directly into the later OSS and CIA efforts explored in our guide to polygraph testing in the 1940s.

The 1915 Harvard Experiments

The most direct link between wartime intelligence needs and scientific deception detection research comes from William Moulton Marston (1893–1947), a psychology student at Harvard University. While an undergraduate, Marston worked in the Harvard Psychological Laboratory under the influence of Hugo Münsterberg, the pioneering German-American psychologist who directed the lab [9]Verified William Moulton Marston — Britannica
Confirms Marston's experiments began under Hugo Münsterberg at Harvard and that he offered his services to the U.S. government during WWI [10]Verified Hugo Münsterberg — Wikipedia
Confirms Münsterberg was an academic mentor to Marston and died in December 1916 from an intracerebral haemorrhage at Harvard. Münsterberg was himself interested in lie detection through physiological indicators and had advocated for the application of psychological methods to forensic problems in his landmark 1908 book On the Witness Stand [11]Verified On the Witness Stand: Essays on Psychology and Crime
Confirms Münsterberg's 1908 book is the foundational text of forensic psychology covering detection of crime and witness memory.

In 1915, Marston began working on his blood pressure approach to deception as a graduate student under Münsterberg's direction in the Harvard Psychological Laboratory [12]Verified Appendix E: Historical Notes on the Modern Polygraph — National Academies
Confirms Marston began deception research in 1915 under Münsterberg at Harvard and submitted proposals to the National Research Council in 1917. His key innovation was the systematic use of a standard sphygmomanometer — a blood pressure cuff — to measure systolic blood pressure changes during questioning [13]Verified Dr. William Moulton Marston — Discontinuous Systolic Blood Pressure Test
Confirms Marston used a standard sphygmomanometer for intermittent systolic blood pressure measurements during questioning. He developed the Discontinuous Systolic Blood Pressure Test, taking intermittent readings of subjects' systolic blood pressure during examination to detect deception [13]Verified Dr. William Moulton Marston — Discontinuous Systolic Blood Pressure Test
Confirms Marston used a standard sphygmomanometer for intermittent systolic blood pressure measurements during questioning. In tests on fellow students, Marston reported a 96 percent success rate in detecting liars [14]Verified A Brief History of the Lie Detector — IEEE Spectrum
Confirms Marston reported a 96 percent success rate in detecting liars and that Robert Yerkes agreed to sponsor his research through the NRC.

According to his wife Elizabeth Holloway Marston's son, the idea originated when Elizabeth remarked that her blood pressure seemed to climb when she became angry or excited [15]Verified William Moulton Marston — Britannica (detailed)
Confirms Marston earned an A.B. in 1915, law degree in 1918, and Ph.D. in 1921 from Harvard; offered WWI services to the government. Elizabeth, who had graduated from Mount Holyoke College with a degree in psychology, assisted Marston throughout his research [15]Verified William Moulton Marston — Britannica (detailed)
Confirms Marston earned an A.B. in 1915, law degree in 1918, and Ph.D. in 1921 from Harvard; offered WWI services to the government. Marston published his findings in the Journal of Experimental Psychology in 1917 under the title "Systolic Blood Pressure Symptoms of Deception" [16]Verified Systolic Blood Pressure Symptoms of Deception — Harvard Archives
Confirms Marston's 1917 article 'Systolic Blood Pressure Symptoms of Deception' is held in the Harvard Schlesinger Library archives. For more on how Marston's polygraph work inspired his famous comic creation, see Wonder Woman and the Polygraph.

Marston's Military Proposals

After the United States entered the war in April 1917, Marston intensified his efforts to secure military interest in his blood pressure deception test. He contacted the U.S. Department of Science and Research, hoping his invention could help detect espionage [17]Verified Harvard's Real 'Lasso of Truth' — Harvard Crimson
Confirms Marston contacted the U.S. Department of Science and Research during WWI and a subcommittee under Shepard evaluated his proposal. In October 1917, he submitted a proposal to the National Research Council through Robert Yerkes, who had agreed to sponsor more rigorous tests of Marston's research [14]Verified A Brief History of the Lie Detector — IEEE Spectrum
Confirms Marston reported a 96 percent success rate in detecting liars and that Robert Yerkes agreed to sponsor his research through the NRC. A subcommittee chaired by John F. Shepard was established to evaluate Marston's proposal and its potential for deception detection [17]Verified Harvard's Real 'Lasso of Truth' — Harvard Crimson
Confirms Marston contacted the U.S. Department of Science and Research during WWI and a subcommittee under Shepard evaluated his proposal.

Marston wired Yerkes with the message: "Remarkable results thirty deception tests under iron clad precautions" [12]Verified Appendix E: Historical Notes on the Modern Polygraph — National Academies
Confirms Marston began deception research in 1915 under Münsterberg at Harvard and submitted proposals to the National Research Council in 1917. He had carried out work with Harold E. Burt and Leonard T. Troland, followed by testing of 20 cases in Boston Municipal Court, where Marston claimed a 100 percent success rate [14]Verified A Brief History of the Lie Detector — IEEE Spectrum
Confirms Marston reported a 96 percent success rate in detecting liars and that Robert Yerkes agreed to sponsor his research through the NRC [12]Verified Appendix E: Historical Notes on the Modern Polygraph — National Academies
Confirms Marston began deception research in 1915 under Münsterberg at Harvard and submitted proposals to the National Research Council in 1917. However, Shepard was not fully convinced of the method's diagnostic specificity [17]Verified Harvard's Real 'Lasso of Truth' — Harvard Crimson
Confirms Marston contacted the U.S. Department of Science and Research during WWI and a subcommittee under Shepard evaluated his proposal.

Both Marston himself (1938) and historian Geoffrey Bunn (1997) refer to Marston having used his test on spies during the wartime period, though no operational details are available [12]Verified Appendix E: Historical Notes on the Modern Polygraph — National Academies
Confirms Marston began deception research in 1915 under Münsterberg at Harvard and submitted proposals to the National Research Council in 1917. During World War I, Marston offered his services to the U.S. government in hopes that his experiments could detect espionage, and there is some evidence that the government took him up on his offer [15]Verified William Moulton Marston — Britannica (detailed)
Confirms Marston earned an A.B. in 1915, law degree in 1918, and Ph.D. in 1921 from Harvard; offered WWI services to the government.

The fact that the war ended in November 1918 before Marston could conduct large-scale military trials meant that his wartime contribution remained largely theoretical rather than operational — but the connection between scientific deception detection and military intelligence had been firmly established. Marston's work directly inspired John Larson's construction of the first modern polygraph in 1921 [15]Verified William Moulton Marston — Britannica (detailed)
Confirms Marston earned an A.B. in 1915, law degree in 1918, and Ph.D. in 1921 from Harvard; offered WWI services to the government, launching an era of innovation explored in our guide to polygraph development in the 1930s.

Vittorio Benussi and Respiratory Detection of Deception

While Marston was the most prominent figure actively seeking military applications for deception detection, the most significant concurrent European contribution came from Vittorio Benussi (1878–1927), an Italian psychologist of Austrian origin working at the University of Graz [18]Verified Vittorio Benussi — Polygraph UK
Confirms Benussi was one of the first to examine breathing tracings for detecting deception, working at the University of Graz. In 1914 — the very year the war began — Benussi published his groundbreaking findings on the respiratory symptoms of lying (Die Atmungssymptome der Lüge) [19]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Benussi published respiratory symptoms of the lie in 1914 (Die Atmungssymptome der Lüge) and details the polygraph timeline.

Benussi discovered a method for calculating the quotient of inhalation-to-exhalation time as a means of verifying truth and detecting deception [19]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Benussi published respiratory symptoms of the lie in 1914 (Die Atmungssymptome der Lüge) and details the polygraph timeline. Using a Marey pneumograph to record thoracic movements, he measured the "Q quotient" — the ratio of inhalation to exhalation duration — before and after statements [20]Verified Vittorio Benussi — Grokipedia
Confirms Benussi used a Marey pneumograph to record the 'Q quotient' — the ratio of inhalation to exhalation duration — for deception detection. His experiments demonstrated that lying caused emotional changes that resulted in detectable respiratory changes indicative of deception [19]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Benussi published respiratory symptoms of the lie in 1914 (Die Atmungssymptome der Lüge) and details the polygraph timeline. This work provided empirical support for the principle that deception produces distinctive physiological signatures [19]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Benussi published respiratory symptoms of the lie in 1914 (Die Atmungssymptome der Lüge) and details the polygraph timeline.

Benussi's respiratory approach would later be incorporated by John Larson when he built the first modern polygraph in 1921, combining Marston's blood pressure measurements with Benussi's respiratory evidence to create a continuous multi-channel recording device [21]Verified The Truth About The Lie Detector
Confirms Larson added Benussi's respiration evidence to Marston's blood pressure concept to create a continuous multi-channel recording device. Understanding how respiratory patterns factor into modern testing is covered in our guide to Galvanic Skin Response (GSR) in polygraph testing.

Angelo Mosso's Plethysmograph Legacy

Italy, which entered the war in 1915 on the Allied side, had been a leader in physiological research relevant to deception detection since the late 19th century. Angelo Mosso's plethysmograph research had demonstrated that blood volume in the extremities changed in response to emotional stimuli, including the fear and anxiety associated with deception [3]Verified Angelo Mosso (1846–1910)
Confirms Mosso's appointment as professor of physiology at the University of Turin in 1879 and his invention of instruments to measure pulse and blood volume changes. His work at the University of Turin, where his department became known as a "physiological mecca" attracting researchers from across Europe, established that the autonomic nervous system responds to psychological stress in ways that can be measured with mechanical instruments [3]Verified Angelo Mosso (1846–1910)
Confirms Mosso's appointment as professor of physiology at the University of Turin in 1879 and his invention of instruments to measure pulse and blood volume changes.

Although Mosso died in 1910, his students and colleagues continued his research programme during the war years. The Italian military, fighting a brutal campaign on the Alpine and Isonzo fronts, had its own interrogation challenges with captured Austro-Hungarian soldiers from diverse ethnic and linguistic backgrounds. The complexity of interrogating such subjects highlighted the potential value of physiological measures that could transcend language barriers. However, no documented evidence exists that Italian military intelligence formally adopted or tested any physiological deception detection methods during the war — the technology gap between laboratory and field was simply too great.

German Research: Wertheimer and Tatbestandsdiagnostik

In the German-speaking world, Max Wertheimer — who would later become one of the founders of Gestalt psychology — had made a significant contribution to deception detection research before the war. In 1904, Wertheimer and Julius Klein published a landmark paper proposing the use of psychological experiments, particularly word association tests, to assess whether criminal suspects had committed a particular crime [22]Verified Experimental Interrogations: Tatbestandsdiagnostik
Confirms Wertheimer and Klein published their 1904 paper on word association tests for criminal investigation and the rise and decline of Tatbestandsdiagnostik. They christened this method Tatbestandsdiagnostik (roughly, "fact-state diagnostics") [22]Verified Experimental Interrogations: Tatbestandsdiagnostik
Confirms Wertheimer and Klein published their 1904 paper on word association tests for criminal investigation and the rise and decline of Tatbestandsdiagnostik.

Their proposal generated enormous interest. Over the following months and years, almost every German-language journal on psychology or criminal law published something on Tatbestandsdiagnostik [22]Verified Experimental Interrogations: Tatbestandsdiagnostik
Confirms Wertheimer and Klein published their 1904 paper on word association tests for criminal investigation and the rise and decline of Tatbestandsdiagnostik. Word association techniques were used to detect lying by investigating differential reaction times to stimuli associated with material about which an individual hoped to deceive [23]Verified On the Detection of Deception (Orne et al.)
Confirms word association techniques by Jung (1906) and Wertheimer & Klein (1904) were used to detect lying by investigating differential reaction times. However, by the advent of World War I, most psychologists and jurists had concluded that the association method was of limited practical use in legal and police practice [22]Verified Experimental Interrogations: Tatbestandsdiagnostik
Confirms Wertheimer and Klein published their 1904 paper on word association tests for criminal investigation and the rise and decline of Tatbestandsdiagnostik.

Nevertheless, the conceptual framework of using reaction times and word associations to detect concealed knowledge would later evolve into the Guilty Knowledge Test (now called the Concealed Information Test), which remains an important research paradigm in polygraph science today. For more on how these early techniques compare to modern approaches, see our guide to comparison questions in polygraph testing.

Bridging Laboratory and Practical Application

Hugo Münsterberg (1863–1916), Marston's mentor at Harvard, was one of the most influential advocates for applying psychological science to practical problems [10]Verified Hugo Münsterberg — Wikipedia
Confirms Münsterberg was an academic mentor to Marston and died in December 1916 from an intracerebral haemorrhage at Harvard. Originally published in 1908, his book On the Witness Stand is considered the foundational text of forensic psychology, applying experimental methods to the courtroom [11]Verified On the Witness Stand: Essays on Psychology and Crime
Confirms Münsterberg's 1908 book is the foundational text of forensic psychology covering detection of crime and witness memory. The book addressed the memory of witnesses, the detection of crime, untrue confessions, and the prevention of crime [11]Verified On the Witness Stand: Essays on Psychology and Crime
Confirms Münsterberg's 1908 book is the foundational text of forensic psychology covering detection of crime and witness memory.

Münsterberg promoted the idea that scientific psychology had much to offer the military, the courts, and industry. He advocated for the use of blood pressure and other physiological changes as a deception gauge as early as 1908 [24]Verified You can't do that! Hugo Münsterberg and misapplied psychology
Confirms Münsterberg proposed using blood pressure and other physiological changes as deception gauges in 1908 and that Marston worked in his lab. His intellectual framework — that psychology should move from the laboratory to practical settings — created institutional acceptance for applying psychological methods to intelligence and security problems.

Münsterberg's career was complicated by WWI itself. Torn between his loyalty to the United States and his German homeland, he often defended Germany's actions, attracting suspicion and criticism [10]Verified Hugo Münsterberg — Wikipedia
Confirms Münsterberg was an academic mentor to Marston and died in December 1916 from an intracerebral haemorrhage at Harvard. Some colleagues at Harvard disassociated themselves from him, and there were threats against his life [10]Verified Hugo Münsterberg — Wikipedia
Confirms Münsterberg was an academic mentor to Marston and died in December 1916 from an intracerebral haemorrhage at Harvard. He died suddenly of an intracerebral haemorrhage while lecturing at Radcliffe College in December 1916 [10]Verified Hugo Münsterberg — Wikipedia
Confirms Münsterberg was an academic mentor to Marston and died in December 1916 from an intracerebral haemorrhage at Harvard — before seeing his vision of applied deception detection begin to materialise in military contexts.

Münsterberg's legacy profoundly shaped the trajectory of polygraph science. His student Marston carried forward the vision of practical deception detection, while the broader applied psychology movement he championed would eventually produce the institutional frameworks — from the APA's first polygraph standards to military testing programmes — that define the profession today.

Why Laboratory Methods Could Not Reach the Trenches

The gap between laboratory deception detection and field application during 1914–1918 was fundamentally unbridgeable. Every instrument available — Lombroso's hydrosphygmograph, Mosso's plethysmograph, Benussi's pneumograph, Marston's sphygmomanometer setup — required conditions impossible to achieve in forward areas where prisoner interrogation typically occurred.

The practical barriers were formidable. The instruments were delicate and bulky, requiring careful calibration and quiet, controlled environments. A captured soldier — physically exhausted, psychologically traumatised, potentially wounded, and questioned through an interpreter in a noisy forward area — presented a very different challenge than a university student participating in a controlled experiment. Language barriers complicated every aspect of testing, as physiological responses could easily be triggered by confusion or translation difficulties rather than deception.

The various types of lie detector machines that existed in this period were laboratory curiosities, not field-deployable tools. It would take John Larson's 1921 invention of the continuous-recording polygraph [25]Verified John Augustus Larson — Wikipedia
Confirms Larson invented the first modern polygraph in 1921 at Berkeley under Chief August Vollmer; original instrument now at the Smithsonian — followed by Leonarde Keeler's development of a truly portable instrument in the mid-1920s [26]Verified Polygraph — Wikipedia
Confirms Keeler added galvanic skin response in 1938-1939 and patented the prototype of the modern polygraph — before deception detection technology became practical for real-world use. The journey from WWI-era science to operational polygraph programmes is a testament to the decades of engineering and methodological refinement that lay ahead.

Available Instruments and Their Constraints

The instruments available for deception detection during WWI each had significant limitations that prevented field deployment:

Lombroso's hydrosphygmograph required the subject to immerse a fist in a sealed water-filled container while fluctuations were recorded on a smoked drum [1]Verified Lombroso's Hydrosphygmograph and Early Deception Detection
Confirms Lombroso used a hydrosphygmograph to measure blood pressure and pulse changes in criminal suspects, published in 1895. It was fragile, difficult to calibrate, and entirely impractical outside a stationary laboratory.

Mosso's plethysmograph measured slow changes in the volume of blood vessels and was designed for research on brain pulsations and circulation [3]Verified Angelo Mosso (1846–1910)
Confirms Mosso's appointment as professor of physiology at the University of Turin in 1879 and his invention of instruments to measure pulse and blood volume changes. It was a sophisticated research instrument unsuited to interrogation settings.

Benussi's pneumograph, while simpler than the cardiovascular instruments, required careful placement and reading conditions to calculate the inhalation-to-exhalation ratio [20]Verified Vittorio Benussi — Grokipedia
Confirms Benussi used a Marey pneumograph to record the 'Q quotient' — the ratio of inhalation to exhalation duration — for deception detection. The interpretation demanded trained expertise that battlefield interrogators lacked.

Marston's sphygmomanometer approach was the most portable of the options, using a standard blood pressure cuff and stethoscope to take intermittent readings [13]Verified Dr. William Moulton Marston — Discontinuous Systolic Blood Pressure Test
Confirms Marston used a standard sphygmomanometer for intermittent systolic blood pressure measurements during questioning. However, it still required a quiet environment, a cooperative subject, and a skilled examiner. His method involved four phases — a quiet period, free narrative, cross-examination, and a final quiet period — with blood pressure measurements plotted over time [27]Verified History of Polygraph — Wilber
Confirms Marston developed his technique while working at the Harvard Laboratory under Hugo Münsterberg and details the four-phase testing method.

None of these instruments could record multiple physiological channels simultaneously. It was not until Larson combined cardiovascular and respiratory measurements into a single continuous-recording device in 1921 that the modern polygraph was born [25]Verified John Augustus Larson — Wikipedia
Confirms Larson invented the first modern polygraph in 1921 at Berkeley under Chief August Vollmer; original instrument now at the Smithsonian. Keeler's later addition of the psychogalvanometer — measuring changes in galvanic skin resistance — in 1938 completed the triad of measurements that define the polygraph as we know it today [26]Verified Polygraph — Wikipedia
Confirms Keeler added galvanic skin response in 1938-1939 and patented the prototype of the modern polygraph.

How Wartime Urgency Shaped Polygraph Science

Although no operational deception detection testing occurred on WWI battlefields, the war's impact on the development of polygraph science was profound and enduring. The conflict accelerated research timelines, created institutional relationships between scientists and military officials, and demonstrated the urgent need for reliable deception detection tools.

Marston's wartime contacts with military intelligence through the National Research Council planted seeds that would germinate into formal military polygraph programmes [12]Verified Appendix E: Historical Notes on the Modern Polygraph — National Academies
Confirms Marston began deception research in 1915 under Münsterberg at Harvard and submitted proposals to the National Research Council in 1917. The war also demonstrated to governments that scientific psychology could serve national security objectives — a lesson that would be applied extensively in World War II, when the OSS and later the CIA would develop systematic polygraph screening programmes, as detailed in our guide to the DIA polygraph programme.

The research momentum generated during WWI carried directly into the 1920s innovations. John Larson, building on Marston's blood pressure concept and adding Benussi's respiratory measurements, constructed the first continuous-recording polygraph in 1921 while working with the Berkeley Police Department under Chief August Vollmer [25]Verified John Augustus Larson — Wikipedia
Confirms Larson invented the first modern polygraph in 1921 at Berkeley under Chief August Vollmer; original instrument now at the Smithsonian. Larson's instrument — the "cardio-pneumo psychogram" — simultaneously measured pulse rate, blood pressure, and respiratory rate during questioning [25]Verified John Augustus Larson — Wikipedia
Confirms Larson invented the first modern polygraph in 1921 at Berkeley under Chief August Vollmer; original instrument now at the Smithsonian. His original polygraph now resides at the Smithsonian Institution in Washington, D.C. [25]Verified John Augustus Larson — Wikipedia
Confirms Larson invented the first modern polygraph in 1921 at Berkeley under Chief August Vollmer; original instrument now at the Smithsonian.

Leonarde Keeler, Larson's protégé, subsequently made the instrument portable and added the galvanic skin response channel in 1938 [26]Verified Polygraph — Wikipedia
Confirms Keeler added galvanic skin response in 1938-1939 and patented the prototype of the modern polygraph, creating the prototype of the modern polygraph. Keeler went on to found the first polygraph school in Chicago in 1948 [26]Verified Polygraph — Wikipedia
Confirms Keeler added galvanic skin response in 1938-1939 and patented the prototype of the modern polygraph, beginning the professionalisation of the field described in our guide to Fred Inbau and the Chicago School of Forensic Science.

The evolution from WWI-era laboratory science to standardised testing protocols would continue through the development of the Relevant-Irrelevant Test, the Control Question Technique, and eventually the Utah Zone Comparison Test. Field validity studies have since demonstrated CQT accuracy rates ranging from 90–98% in real criminal investigations [28]Verified Review of 12 Field Validity Studies of CQT
APA-commissioned review concluding CQT accuracy in real-life applications ranged from 92–98%, demonstrating the validity of techniques built on WWI-era foundations [29]Verified Review of Field Studies of CQT Since 1988
Review producing overall accuracy of 90.5% across field studies, validating the physiological principles first explored during WWI era, vindicating the foundational premise established by the WWI-era pioneers: that deception produces measurable physiological changes that trained examiners can detect. Military polygraph programmes, including those in Korea and Turkey, trace their institutional lineage back to these wartime origins.