Beyond the Polygraph: Deception Detection and the Autonomic Nervous System

Polygraphy Pitfalls

Polygraphy presupposes that the subject will have a consistent and measurable physiologic response when he or she attempts to deceive the interviewer. The changes in BP, heart rate, respirations, and perspiration that are detected by polygraphy and interpreted by the examiner are controlled by the ANS (Table 1). There are a variety of diseases that are known to cause autonomic dysfunction (dysautonomia). Small fiber autonomic neuropathies often result in loss of sweating and altered heart rate and BP variation and can arise from many underlying conditions. Synucleinopathies, such as Parkinson disease, alter cardiovascular reflexes.^14,16

Even diseases not commonly recognized as having a predominant clinical impact on ANS function can demonstrate measurable physiologic effect. For example, approximately 60% of patients with rheumatoid arthritis will have blunted cardiovagal baroreceptor responses and heart rate variability.¹⁷ ANS dysfunction is also a common sequela of alcoholism.¹⁸ Patients with diabetes mellitus often have an elevated resting heart rate and low heart rate variability due to dysregulated β-adrenergic activity.¹⁹ The impact of reduced baroreceptor response and reduced heart rate variability could impact the polygraph interpreter’s ability to discern responses using heart rate. Individuals with ANS dysfunction that causes blunted physiologic responses could have inconclusive or potentially worse false-negative polygraph results due to lack of variation between control and target questions.

To our knowledge, no study has been performed on the validity of polygraphy in patients with any form of dysautonomia. Additionally, a 2011 process and compliance study of the DoD polygraph program specifically recommended that “adjudicators would benefit from training in polygraph capabilities and limitations.”²⁰ Although specific requirements vary from program to program, all programs accredited by the American Polygraph Association provide training in physiology, psychology, and standardization of test results.

Many commonly prescribed medications have effects on the ANS that could affect the results of a polygraph exam (Table 2). For example, β blockers reduce β adrenergic receptor activation in cardiac muscle and blood vessels, reducing heart rate, heart rate variability, cardiac contractility, and BP.²¹ This class of medication is prescribed for a variety of conditions, including congestive heart failure, hypertension, panic disorder, and posttraumatic stress disorder. Thus, a patient taking β blockers will have a blunted physiologic response to stress and have an increased likelihood of an inconclusive or false-negative polygraph exam.

Some over-the-counter medications also have effects on autonomic function. Sympathomimetics such as pseudoephedrine or antihistamines with anticholinergic activity like diphenhydramine can both increase heart rate and BP.^22,23 Of the 10 most prescribed medications of 2016, 5 have direct effects on the ANS or the variables measured by the polygraph machine.²⁴ An exhaustive list of medication effects on autonomic function is beyond the scope of this article.

A medication that may affect the results of a polygraph study that is of special interest to the DoD and military is mefloquine. Mefloquine is an antimalarial drug that has been used by military personnel deployed to malaria endemic regions.²⁵ In murine models, mefloquine has been shown to disrupt autonomic and respiratory control in the central nervous system.²⁶ The neuropsychiatric adverse effects of mefloquine are well documented and can last for years after exposure to the drug.²⁷ Therefore, mefloquine could affect the results of a polygraph test through both direct toxic effects on the ANS as well as causing anxiety and depression, potentially affecting the subject’s response to questioning.