Original Research

Beyond the Polygraph: Deception Detection and the Autonomic Nervous System

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The polygraph and other emerging technologies are used to aid in the interrogation and screening of employees, but examiners and physicians should be aware that results are vulnerable to inaccuracies in subjects with autonomic disorders and may be confounded by multiple medications.



The US Department of Defense (DoD) and law enforcement agencies around the country utilize polygraph as an aid in security screenings and interrogation. It is assumed that a person being interviewed will have a visceral response when attempting to deceive the interviewer, and that this response can be detected by measuring the change in vital signs between questions. By using vital signs as an indirect measurement of deception-induced stress, the polygraph machine may provide a false positive or negative result if a patient has an inherited or acquired condition that affects the autonomic nervous system (ANS).

A variety of diseases from alcohol use disorder to rheumatoid arthritis can affect the ANS. In addition, a multitude of commonly prescribed drugs can affect the ANS. Although in their infancy, functional magnetic resonance imaging (fMRI) and EEG (electroencephalogram) deception detection techniques circumvent these issues. Dysautonomias may be an underappreciated cause of error in polygraph interpretation. Polygraph examiners and DoD agencies should be aware of the potential for these disorders to interfere with interpretation of results. In the near future, other modalities that do not measure autonomic variables may be utilized to avoid these pitfalls.


Throughout history, humans have been interested in techniques and devices that can discern lies from the truth. Even in the ancient era, it was known that the act of lying had physiologic effects. In ancient Israel, if a woman accused of adultery should develop a swollen abdomen after drinking “waters of bitterness,” she was considered guilty of the crime, as described in Numbers 5:11-31. In Ancient China, those accused of fraud would be forced to hold dry rice in their mouths; if the expectorated rice was dry, the suspect was found guilty.1 We now know that catecholamines, particularly epinephrine, secreted during times of stress, cause relaxation of smooth muscle, leading to reduced bowel motility and dry mouth.2-4 However, most methods before the modern era were based more on superstition and chance rather than any sound physiologic premise.

When asked to discern the truth from falsehood based on their own perceptions, people correctly discern lies as false merely 47% of the time and truth as nondeceptive about 61% of the time.5 In short, unaided, we are very poor lie detectors. Therefore, a great deal of interest in technology that can aid in lie detection has ensued. With enhanced technology and understanding of human physiology came a renewed interest in lie detection. Since it was known that vital signs such as blood pressure (BP), heart rate, and breathing could be affected by the stressful situation brought on by deception, quantifying and measuring those responses in an effort to detect lying became a goal. In 1881, the Italian criminologist Cesare Lombroso invented a glove that when worn by a suspect, measured their BP.6-8 Changes in BP also were the target variable of the systolic BP deception test invented by William M. Marston, PhD, in 1915.8 Marston also experimented with measurements of other variables, such as muscle tension.9 In 1921, John Larson invented the first modern polygraph machine.7


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