Can You Beat a Polygraph? Myths, Evidence, Research

This post synthesises the countermeasures research reviewed in Raymond Nelson’s 2015 paper “Scientific Basis for Polygraph Testing” (Polygraph, 44(1), 28–61, pp. 46–48) together with the findings of the National Research Council (2003). Full citation details appear at entry 1 of the Sources list.

Key Takeaways

Simply knowing how a polygraph works does not enable an examinee to defeat it.^[1]
Neither hypnosis nor common pharmaceutical drugs have been shown to defeat polygraph testing reliably.^[2]
Trained physical and mental countermeasures can reduce polygraph accuracy, but the claim that it is easy to defeat both the instrument and a trained examiner lacks scientific support.^[3]
Truthful examinees who attempt countermeasures increase their risk of being wrongly classified as deceptive.^[4]
Activity sensors, mandatory since 2012, have improved examiners’ ability to detect countermeasure attempts.^[5]

Why People Ask This Question

“Can you beat a polygraph?” is one of the most frequently searched questions about polygraph testing, and it deserves a careful, evidence-based answer. People who ask it are not all would-be deceivers. Many are truthful individuals facing a forthcoming examination — in employment, family court, or post-conviction supervision — who are anxious about the possibility of a false result. Others are simply curious about the limits of any psychophysiological measurement.

Both groups deserve honest information. The internet is saturated with unsubstantiated advice — some claiming that polygraphs are trivially easy to defeat, some claiming they are impossible to fool. Neither extreme is supported by the peer-reviewed literature. This post examines what the research actually shows, drawing on the systematic review in Nelson (2015) and the conclusions of the United States National Research Council (NRC, 2003).

What Are Polygraph Countermeasures?

In polygraph research, the term countermeasure (CM) refers to any deliberate action taken by an examinee with the intention of altering the physiological data the instrument records, so as to produce a non-deceptive outcome despite the presence of deception — or, in some cases, to disrupt the test entirely. Countermeasures are typically categorised as:

Informational — learning how the test works in the hope that knowledge alone will allow manipulation.
Pharmacological — taking drugs (sedatives, stimulants, beta-blockers) to dampen or alter autonomic responses.
Hypnotic — using post-hypnotic suggestion to alter recall or arousal.
Physical — deliberate muscular actions (e.g. tongue biting, toe pressing) timed to specific questions to augment responses to comparison questions.
Mental — cognitive tasks (e.g. mental arithmetic, imagery) performed during comparison questions to create artificial arousal.

The research evidence on each category differs markedly.

Information Alone Does Not Defeat the Test

A common assumption is that understanding how a polygraph works is sufficient to defeat it. The evidence does not support this. Rovner (1979, 1986) and Rovner, Raskin and Kircher (1979) examined whether providing participants with detailed information about polygraph testing procedures enabled them to alter their test outcomes. The finding was clear: information alone was insufficient to alter polygraph accuracy.^[1]

This is an important finding because a great deal of online “advice” about defeating polygraphs amounts to no more than descriptions of how the comparison question technique works. According to this line of research, reading such material does not, by itself, confer the ability to manipulate one’s own physiological responses under examination conditions.

Hypnosis and Drugs: Largely Ineffective

Hypnosis

Timm (1991) investigated whether post-hypnotic suggestion could be used to alter polygraph outcomes. The finding was that it could not: post-hypnotic suggestion was ineffective as a polygraph countermeasure.^[6]

Pharmaceutical Drugs

Two studies by Iacono and colleagues examined the effects of commonly discussed drug classes. Iacono, Boisvenu and Fleming (1984) and Iacono, Cerri, Patrick and Fleming (1992) found that neither benzodiazepines (a class of sedative) nor stimulants were effective at defeating polygraph testing.^[7]

One Partial Exception

Waid, Orne and Orne (1981) found that meprobamate, an older anxiolytic, may affect polygraph recordings.^[8] This drug is now rarely prescribed in the United Kingdom. The broader pattern across the pharmacological research is that commonly available drugs do not reliably defeat polygraph testing.

Trained Physical and Mental Countermeasures

The picture is more nuanced when it comes to deliberate physical and mental countermeasures applied after specific training. Honts, Raskin and Kircher (1994) found that both physical countermeasures (such as pressing a toe against the floor during comparison questions) and mental countermeasures (such as performing mental arithmetic during comparison questions) were equally effective at reducing polygraph accuracy.^[9]

This is the finding most often cited by those who argue that polygraphs are easily defeated. However, two critical qualifications must be noted.

Qualification 1: Examiner Detection

Can examiners detect when someone is using countermeasures? The evidence is mixed. Honts (1987) found that examiners were not as effective as claimed at detecting countermeasure use.^[10] This suggests that a trained, determined individual could, under certain conditions, reduce test accuracy without detection. However, this finding predates the introduction of activity sensors (discussed below), which have materially altered the detection landscape.

Qualification 2: Spontaneous Countermeasures Are Not Uncommon

Honts, Raskin, Kircher and Hodes (1988) found that spontaneous countermeasure behaviour — untrained, instinctive attempts to influence the test — is not uncommon among examinees.^[11] This means that some degree of countermeasure activity is part of the normal baseline of examinations, and experienced examiners account for it in their assessment.

The Critical Finding: Truthful Examinees at Greater Risk

Perhaps the most important finding in the countermeasures literature — and the one most relevant to anxious truthful examinees — is this: truthful people who attempt countermeasures increase their risk of being classified as deceptive.

Rovner (1979) and Honts and Amato (2001) both found that truthful participants who attempted countermeasures received more deceptive classifications than truthful participants who did not.^[4] The NRC (2003) also noted this risk, observing that countermeasure attempts may pose a greater threat to the accuracy of results for truthful examinees than for deceptive ones.^[12]

Misconception: “If I’m Truthful, Countermeasures Can’t Hurt Me”

The opposite is true. The comparison question technique relies on differential physiological responding between different types of question. When a truthful examinee artificially augments responses to comparison questions — which is precisely what most physical and mental countermeasures attempt — the resulting pattern can mimic the profile of a deceptive examinee. The research consistently shows that truthful countermeasure use increases false-positive rates.

Activity Sensors and Countermeasure Detection

Much of the early countermeasures research was conducted before the widespread adoption of activity sensors — devices that detect muscular movement, pressure, and postural changes that may indicate physical countermeasure use. Stephenson and Barry (1986) and Ogilvie and Dutton (2008) found that activity sensors improve the detection of countermeasure attempts.^[5]

Recognising their value, the American Polygraph Association (APA) mandated the use of activity sensors from 1 January 2012.^[13] Any examination conducted in accordance with contemporary Standards of Practice will therefore employ these sensors, materially reducing the window for undetected physical countermeasures compared with the studies from the 1980s and 1990s that are most often cited by critics.

What the National Research Council Concluded

The most authoritative independent review of polygraph science remains the 2003 report by the National Research Council of the United States National Academies. On the subject of countermeasures, the NRC stated:

“Because the effective application of mental or physical countermeasures on the part of examinees would require skill in distinguishing between relevant and comparison questions, skill in regulating physiological response, and skill in concealing countermeasures from trained examiners, claims that it is easy to train examinees to beat both the polygraph and trained examiners require scientific supporting evidence to be credible. However, we are not aware of any such research.”^[3]

This conclusion is carefully worded. The NRC did not say countermeasures are impossible. It said that the claim they are easy to learn and apply successfully against both the instrument and a trained examiner has no supporting scientific evidence. The distinction matters: it acknowledges a theoretical vulnerability whilst noting the absence of evidence that this vulnerability is routinely exploitable in practice.

What This Means for You

If you are facing a polygraph examination — whether in a family law matter, as part of post-conviction supervision, or in any other context — the research evidence points to clear practical conclusions.

Summary of Countermeasure Research Findings
Countermeasure Type	Effective at Defeating Polygraph?	Risk to Truthful Examinees
Information alone	No^[1]	Low direct risk, but may increase anxiety
Hypnosis	No^[6]	Uncertain
Drugs (benzodiazepines, stimulants)	No^[7]	May impair cooperation and communication
Trained physical CM	Can reduce accuracy^[9]	High — increases false-deceptive risk^[4]
Trained mental CM	Can reduce accuracy^[9]	High — increases false-deceptive risk^[4]

If You Are Truthful

Do not attempt countermeasures. The evidence is consistent: truthful examinees who try to manipulate their responses are more likely to be classified as deceptive. The best course of action is to answer questions honestly and allow your natural physiological responses to speak for themselves.

If You Are Anxious

Anxiety about the process is normal and expected. A competent examiner will conduct a thorough pre-test interview to explain the procedure, discuss the questions in advance, and address any concerns. If you have questions about your rights during an examination, ask before the test begins. Openness with the examiner is far more protective than any countermeasure technique.

If You Are Considering Substances

Do not take any medication or substance specifically to influence a polygraph result. Beyond the evidence that common drugs are ineffective, undisclosed substance use may constitute a breach of the conditions of your examination and could raise separate legal or supervisory issues.

No Test Is Infallible

Honesty about the limits of polygraph testing is essential. No psychophysiological measurement is perfectly accurate. The NRC (2003) acknowledged both the utility and the limitations of the technique. Polygraph testing produces probabilistic, not certain, outcomes. False positives (truthful people classified as deceptive) and false negatives (deceptive people classified as truthful) occur in every application of the method.

What the countermeasures evidence does not support, however, is the claim that polygraph testing can be routinely and easily defeated by anyone who reads a website or watches a tutorial video. The research shows that most commonly discussed countermeasure strategies — information, hypnosis, drugs — are simply ineffective. Those that can affect results — trained physical and mental techniques — require specific skills, carry a substantial risk of detection (especially with activity sensors), and paradoxically harm truthful examinees most.

The Bottom Line

Systematic defeat of polygraph testing by untrained individuals is not supported by peer-reviewed evidence. Trained countermeasures can reduce accuracy, but the claim that this is easy or reliable remains, in the words of the NRC, without “scientific supporting evidence to be credible.” For truthful examinees, attempting any countermeasure is the single most counterproductive step they can take.

Glossary

CM (Countermeasure): Any deliberate action taken by an examinee to alter the physiological data recorded during a polygraph examination, with the aim of producing a non-deceptive result.
CQT (Comparison Question Technique): A polygraph testing format that compares physiological responses to relevant questions (about the matter under investigation) with responses to comparison questions (broader questions designed to elicit some concern in truthful examinees).
RQ (Relevant Question): A question in a polygraph examination that directly addresses the matter under investigation (e.g. “Did you commit [the act in question]?”).
CQ (Comparison Question): A question in a CQT examination designed to serve as a physiological comparison. It is typically broader and less specific than the relevant question.
Activity Sensor: A device attached to or placed beneath the examinee during a polygraph examination to detect deliberate muscular movements, postural shifts, or pressure changes that may indicate physical countermeasure use.
EDA (Electrodermal Activity): Changes in the electrical conductivity of the skin, primarily caused by sweat gland activity. EDA is one of the key physiological channels measured during polygraph testing.
ANS (Autonomic Nervous System): The part of the nervous system that controls involuntary bodily functions such as heart rate, respiration, and perspiration. Polygraph instruments measure ANS-mediated responses.
False Positive: An outcome in which a truthful examinee is incorrectly classified as deceptive. Also termed a false-deceptive result.
False Negative: An outcome in which a deceptive examinee is incorrectly classified as truthful. Also termed a false-non-deceptive result.
NRC (National Research Council): The principal operating arm of the United States National Academies of Sciences, Engineering, and Medicine. The NRC published a major review of polygraph science in 2003.
APA (American Polygraph Association): A US-based professional organisation for polygraph examiners. The APA sets standards of practice and accreditation requirements for its members. It mandated activity sensor use from 2012.
BPS (British Polygraph Society): A UK membership body for polygraph professionals, founded in 2017. BPS is not a statutory regulator.
PCSOT (Post-Conviction Sex Offender Testing): The use of polygraph testing as part of the supervision and treatment of convicted sex offenders, typically following release on licence.
HMPPS (His Majesty’s Prison and Probation Service): The executive agency of the Ministry of Justice responsible for the administration of prisons and probation services in England and Wales, including the statutory polygraph regime.

Nelson, R. (2015). Scientific Basis for Polygraph Testing. Polygraph, 44(1), 28–61 (countermeasures section, pp. 46–48). Available at: polygraph.org.
National Research Council. (2003). The Polygraph and Lie Detection. Washington, DC: The National Academies Press, p. 147.

This post is a research summary intended for general information. It does not constitute legal advice, clinical guidance, or an endorsement of any particular polygraph technique. Polygraph testing in England and Wales is subject to statutory regulation under the Offender Management Act 2007 (ss. 28–30) and the Domestic Abuse Act 2021 (s. 76), administered by HMPPS. Individuals with specific concerns about a forthcoming or past examination should seek independent professional advice.