Pathological Liars & Polygraph Tests: Can They Be Caught?

The Spectrum of Human Deception

Not all lies are created equal, and neither are the people who tell them. The spectrum of human deception spans from harmless social fibbing to deeply entrenched pathological behaviour that can destroy lives and relationships. Understanding where different liars fall on this spectrum is essential before we can address whether a polygraph test can effectively identify them.

Consider two scenarios: telling your employer you were late because of traffic when you actually overslept, versus someone who fabricates an entirely false public persona and maintains it for years in front of millions of people. These situations occupy vastly different positions on the deception spectrum, and the psychological mechanisms behind them are fundamentally different.

In the first scenario, you likely felt guilt. You may have spent the day worrying about whether your boss believed you. In the second scenario, the deceiver often feels nothing of the sort. They operate from an entirely different psychological framework — one that makes them uniquely challenging subjects in a polygraph examination.

How Common Is Everyday Lying?

White lies are the social currency of human interaction — small, often benign falsehoods we tell to smooth over awkward situations or spare someone's feelings. Research by psychologist Robert Feldman at the University of Massachusetts found that 60% of people lied at least once during a 10-minute conversation with a stranger, telling an average of two to three lies [6]Verified Self-Presentation and Verbal Deception: Do Self-Presenters Lie More?
Confirms 60% of people lied at least once during a 10-minute conversation, averaging two to three lies. While this is sometimes simplified as "everyone lies constantly," more recent studies have found that the majority of people actually report telling no lies in a typical day, while a small subset of prolific liars account for most of the deception [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day.

These everyday lies serve a social function. When your partner asks if an outfit looks good and you enthusiastically agree despite private reservations, you are choosing relationship harmony over brutal honesty. When a colleague asks if you enjoyed their presentation and you say it was great, you are maintaining a functional working relationship.

The Physiological Cost of Significant Lies

Where things become more significant is when an ordinary person tells a lie with real consequences. Someone involved in a car accident who tells the responding officer they were not on their phone, when in reality they were texting, carries a lie with real legal and moral weight. Such a person may develop physical symptoms of anxiety: digestive distress, elevated heart rate, tension headaches, and a persistent sense of dread.

This physiological stress response is precisely what makes the average person detectable on a polygraph examination. The body rebels against the mind's attempt to conceal the truth, producing measurable changes in heart rate, blood pressure, respiration, and electrodermal activity. For most people, lying about something important creates a physiological signature that a well-calibrated polygraph instrument can capture. To understand the science behind this, see our guide to the psychological and physiological foundations of polygraph testing.

The reason most people cannot successfully deceive a polygraph is that their autonomic nervous system treats deception as a threat. The sympathetic branch does not distinguish between the stress of physical danger and the stress of being caught in a lie — both trigger the same cascade of cortisol and adrenaline that produce measurable physiological changes a polygraph examiner is trained to interpret.

The Compulsive Lying Pattern

Compulsive liars occupy a middle ground between innocent white-lie tellers and pathological liars. These individuals have developed a habitual pattern of deception that goes beyond occasional social fibbing but does not quite reach the pathological threshold. They chronically embellish facts, exaggerate accomplishments, and position themselves as the most important person in any room.

The critical distinction between compulsive and pathological liars lies in what happens when they are caught. Compulsive liars, while comfortable with deception in their daily lives, typically fold under direct questioning. When confronted with irrefutable evidence of their dishonesty, they will usually admit to their transgressions and feel shame and embarrassment. This capacity for shame and behavioural adjustment is what keeps compulsive liars outside the pathological category. For a deeper exploration of this distinction, see our guide on catching a compulsive liar with a lie detector test.

Compulsive Liars and Polygraph Testing

From a polygraph perspective, compulsive liars present a moderate challenge. Their comfort with deception means they may not produce the dramatic physiological responses that an occasional liar would. However, because they retain the capacity for guilt and shame, and because they know on some level that what they are saying is untrue, a skilled examiner can typically detect their deception through standard polygraph protocols.

Research on liars' verbal strategies offers additional tools for examiners. Studies have found that liars include fewer verifiable details than truth tellers, and classifying participants by verifiable detail frequency alone achieved 79% accuracy [7]Verified Exploiting liars' verbal strategies by examining the verifiability of details
Confirms liars include fewer verifiable details and that verifiable detail classification alone achieved 79% accuracy. Combined with physiological measurement, this makes compulsive liars significantly more detectable than pathological ones. Compulsive liars still have a functioning stress response to significant lies — their autonomic nervous system still produces detectable signals when the stakes are real.

The Liver King Case Study

To understand the mindset of a pathological liar, consider the case of Brian Johnson, known online as "The Liver King." In November 2022, leaked emails published by the YouTube channel "More Plates More Dates" revealed that Johnson had been spending over $11,000 per month on anabolic steroids [8]Verified Liver King - Wikipedia
Confirms Johnson spent over $11,000 per month on steroids, including 16 vials of performance-enhancing drugs monthly, directly contradicting the core message of his public persona.

Johnson went viral in 2021, building a massive following based on the claim that his extraordinary physique — standing at 5'7" and weighing approximately 190 pounds of lean muscle with extremely low body fat — was achieved entirely through natural means: ancestral living, organ meat consumption, and primal exercise [9]Verified Liver King Height, Weight, & Steroid Scandal
Confirms Liver King stands 5'7" with weight estimated between 180-190 lbs[10]Verified Liver King Height and Weight
Confirms Liver King is 5'7" and weighs approximately 190 lbs, and describes his six-minute confession video. Despite appearing on major podcast platforms where hosts directly challenged him to admit steroid use, Johnson maintained his position with unwavering conviction. He looked interviewers in the eye and repeatedly insisted he was natural.

The Pathological Response to Being Caught

What separates Johnson's behaviour from compulsive lying is what happened after the evidence was made public. Rather than fully coming clean, Johnson released a six-minute video confession [11]Verified 'Liver King' Admits Steroid Use, Calls Persona 'Experiment'
Confirms the six-minute confession video and $11,000/month steroid cost[12]Verified There It Is: Liver King Has Finally Admitted To Using Steroids In A 6-Minute Apology Video
Confirms six-minute video duration and that leaked emails showed Johnson claimed to have been working out 'for 35 years'. In the video, he did not simply admit to the deception for what it was — a business decision to build a $100-million supplement empire on false pretences [13]Verified Liver King leaked steroids email prompts apology from YouTube 'primal living' guru with $100m fitness empire
Confirms Liver King was making $100 million a year selling supplements. Instead, he reframed his lying as an act of service, claiming the Liver King persona was "an experiment to spread the message" about suicide prevention and that "young men are hurting the most, feeling lost, weak and submissive" [14]Verified Liver King apology video — detailed transcript
Confirms Johnson referenced 'young men who are hurting the most, feeling lost, weak and submissive' and his claim about suicide prevention motivation.

In his apology, Johnson claimed he had "convinced myself that this would overshadow the 36 years of working out usually twice a day without PEDs" [15]Verified Liver King Confesses to Steroid Use After Leaked Email
Confirms Johnson's quote about '36 years of working out usually twice a day without PEDs' from his apology video. The leaked emails, however, clearly showed he was using compounds specifically designed for competitive bodybuilding, including multiple steroids and synthetic protein hormones totalling 16 vials per month [8]Verified Liver King - Wikipedia
Confirms Johnson spent over $11,000 per month on steroids, including 16 vials of performance-enhancing drugs monthly. This is the hallmark of pathological lying: when caught, the pathological liar does not stop lying. They dig deeper, constructing new layers of deception on top of the exposed ones.

What Makes Pathological Liars Unique

Pathological liars exhibit several characteristics that set them apart from both white-lie tellers and compulsive liars:

They often experience diminished remorse about their lies, regardless of magnitude. They do not develop the typical stress-related symptoms from living with their falsehoods. When caught, they tend to escalate rather than retreat, constructing additional lies to support the original deception. Their lying is not limited to specific topics but extends across virtually all areas of their life.

Interestingly, research by Curtis and Hart found that pathological liars do experience some distress from their behaviour — those in the pathological lying group indicated that their lying was often out of their control and that lies tend to grow from an initial falsehood, causing further complications [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day. This suggests that pathological lying has compulsive elements rather than being entirely voluntary.

Understanding these characteristics is essential for anyone considering whether a polygraph test might be effective in their specific situation. You can also read more about sociopathic liars and how to identify them.

Brain Structure Differences in Pathological Liars

While research into pathological lying remains limited compared to other behavioural disorders, the studies that do exist reveal fascinating structural differences in the brains of pathological liars. A landmark study by Yang, Raine, and colleagues published in the British Journal of Psychiatry examined brain scans of pathological liars compared to normal control subjects and individuals with antisocial traits [2]Verified Prefrontal white matter in pathological liars
Confirms pathological liars show 22–26% increase in prefrontal white matter and 36–42% reduction in grey/white matter ratio.

The original 2005 study found that pathological liars displayed a 22–26% increase in prefrontal white matter and a 36–42% reduction in the prefrontal grey-to-white matter ratio compared to both normal and antisocial control groups [2]Verified Prefrontal white matter in pathological liars
Confirms pathological liars show 22–26% increase in prefrontal white matter and 36–42% reduction in grey/white matter ratio. A follow-up 2007 study by the same team further localised these increases, finding that the white matter increases were particularly pronounced in the orbitofrontal cortex (22–26% increase), inferior frontal cortex (32–36% increase), and middle frontal cortex (28–32% increase) [16]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms white matter increases localised to orbitofrontal cortex (22–26%), inferior frontal cortex (32–36%), and middle frontal cortex (28–32%).

What the White Matter Increase Means

White matter in the brain consists primarily of myelinated axons — the long fibres that connect different brain regions and facilitate communication between them. An increase in prefrontal white matter suggests enhanced connectivity within the regions responsible for decision-making, planning, and social behaviour.

In practical terms, this may mean that pathological liars have a neurological advantage when it comes to constructing and maintaining deceptions. Their brains may be better wired for the complex cognitive task of lying, which requires simultaneously managing the truth, the fabricated story, the emotional presentation, and monitoring the listener's response.

The Grey Matter Reduction and Amygdala Desensitisation

The reduction in grey matter in the prefrontal cortex is equally significant. Grey matter contains neuronal cell bodies and is associated with functions like self-regulation, moral reasoning, and emotional processing. A reduction in prefrontal grey matter could explain why pathological liars experience diminished guilt, reduced empathy, and a weakened sense of moral consequence.

Additionally, a 2016 study published in Nature Neuroscience by Garrett and Sharot at University College London found that the amygdala — the brain's emotional processing centre — becomes desensitised with repeated lying [5]Verified The brain adapts to dishonesty
Confirms amygdala response to lying declines with repeated dishonesty and larger drops predict bigger future lies. The amygdala responded strongly the first times people lied but its response declined with each subsequent lie, and larger drops in amygdala activity predicted bigger lies in the future [5]Verified The brain adapts to dishonesty
Confirms amygdala response to lying declines with repeated dishonesty and larger drops predict bigger future lies. This provides a neurological explanation for how lying can escalate from small fibs to pathological deception over time.

Together, these structural and functional differences paint a picture of a brain that may be optimised for deception and deficient in the mechanisms that would normally create psychological discomfort about lying. This is not simply a matter of willpower or practice — it appears to be a fundamental difference in brain architecture with profound implications for polygraph testing.

Is Pathological Lying a Mental Illness?

The medical community has not reached a consensus on whether pathological lying should be classified as a standalone mental illness. Pathological lying is not currently listed as an independent disorder in the DSM-5, though it appears as a symptom of other conditions such as antisocial, narcissistic, and histrionic personality disorders [17]Verified Pathological lying - Wikipedia
Confirms pathological lying appears in DSM-5 as a symptom of other disorders and is listed in the PCL-R. However, Curtis and Hart's 2020 research provides empirical support for establishing pathological lying as a distinct diagnostic entity, finding that it meets major nosological definitions of a disorder [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day.

The condition was first described in medical literature in 1891 by psychiatrist Anton Delbrück, who coined the term "pseudologia phantastica" [18]Verified 10 Facts About Pathological Lying
Confirms pathological lying was first described in 1891 by psychiatrist Anton Delbrück as pseudologia phantastica. More recently, research has found that pathological liars tell an average of 10 lies per day, have been doing so for longer than six months, and the onset most commonly occurs during adolescence [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day. A 2026 study from McGill University also found that pathological lying in teenagers is associated with executive function deficits such as poor memory and impulse control [19]Verified Pathological lying in teens is associated with executive function deficits
Confirms pathological lying in teenagers is associated with executive function deficits and that treatments may centre on executive functioning. For additional insight into how personality disorders intersect with lie detection, see our guide on mental health and polygraph testing.

Mental Health Conditions Linked to Pathological Lying

Research identifies several mental health conditions frequently associated with pathological lying patterns. While not every person with these conditions becomes a pathological liar, the correlations are significant enough that clinicians and polygraph examiners should be aware of them.

Borderline Personality Disorder (BPD): Individuals with BPD may engage in pathological lying primarily to avoid abandonment or rejection. Their intense fear of being left alone can drive them to fabricate stories or construct false narratives to maintain relationships. For polygraph examiners, understanding the BPD dynamic is crucial — see our guide to anxiety disorders and polygraph testing for related considerations.

Antisocial Personality Disorder (ASPD): ASPD is perhaps the condition most closely associated with pathological lying. The DSM-5 notes "deceitfulness, as indicated by repeated lying, use of aliases, or conning others for personal profit or pleasure" as a hallmark of antisocial personality [17]Verified Pathological lying - Wikipedia
Confirms pathological lying appears in DSM-5 as a symptom of other disorders and is listed in the PCL-R. The Psychopathy Checklist-Revised (PCL-R) specifically includes pathological lying as one of its 20 items [17]Verified Pathological lying - Wikipedia
Confirms pathological lying appears in DSM-5 as a symptom of other disorders and is listed in the PCL-R. Our detailed examination of sociopathic liars explores this relationship in depth.

Factitious Disorder (Munchausen Syndrome): People with factitious disorder lie specifically to appear ill or to gain sympathy and attention. They may fabricate symptoms, contaminate lab samples, or self-harm to maintain the deception.

Narcissistic Personality Disorder (NPD): Narcissistic individuals lie to manipulate others and maintain their grandiose self-image. Their lies often serve to position themselves as superior and to control how others perceive them.

Childhood Trauma and Development

Not all pathological liars have diagnosable personality disorders. Some develop the behaviour as a coping mechanism in response to childhood experiences. Children who grow up in environments characterised by abuse, emotional neglect, or persistent criticism may learn that deception is their most reliable tool for survival.

For a child who is punished unpredictably, truth-telling becomes dangerous and lying becomes adaptive. Over time, this pattern can become so deeply ingrained that it persists into adulthood long after the original threat has passed. Research suggests the brain may rewire itself during these formative years, and the onset of pathological lying most commonly occurs during adolescence [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day. The 2026 McGill study found evidence of pathological lying among teenagers and also found an association with executive functioning deficits, suggesting that practitioners may be able to consider treatments centred around executive functioning for patients who present such patterns [19]Verified Pathological lying in teens is associated with executive function deficits
Confirms pathological lying in teenagers is associated with executive function deficits and that treatments may centre on executive functioning.

For more on the connection between childhood experiences and deceptive behaviour, see our guide on whether lying is a sign of childhood trauma.

Recognising the Warning Signs

Identifying a pathological liar is challenging precisely because they are often exceptionally skilled at deception. However, research and clinical experience have identified several key indicators:

Extraordinary frequency of lies: Pathological liars tell an estimated 10 or more lies per day, far exceeding the norm [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day[20]Verified Have You Ever Met a Pathological Liar?
Confirms pathological liars tell 10+ lies per day, that 100% of respondents reported primarily self-serving lies, and 91% of people reported encountering a pathological liar. Their lies span virtually all areas of life rather than being confined to specific topics.

Lies that grow and escalate: Research confirms that pathological lying behaviour involves telling lies without a specific reason, with lies growing from an initial falsehood [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day. One lie begets another, creating increasingly complex webs of deception.

Unbelievable stories: Studies found that the most common way people identified pathological liars was because "the lies were so unbelievable" [20]Verified Have You Ever Met a Pathological Liar?
Confirms pathological liars tell 10+ lies per day, that 100% of respondents reported primarily self-serving lies, and 91% of people reported encountering a pathological liar. The grandiosity and implausibility of their claims often becomes their undoing.

Primarily self-serving lies: Research found that 100% of respondents who had encountered a pathological liar indicated the liar told primarily self-serving lies [20]Verified Have You Ever Met a Pathological Liar?
Confirms pathological liars tell 10+ lies per day, that 100% of respondents reported primarily self-serving lies, and 91% of people reported encountering a pathological liar.

Reframing when caught: Rather than admitting fault, pathological liars tend to construct additional layers of explanation. They may portray themselves as victims or reframe their deception as serving a noble purpose.

Absence of typical guilt indicators: Unlike occasional liars, pathological liars may not display the physical signs of discomfort — no averted gaze, no nervous fidgeting, no changes in vocal tone.

If you suspect you are dealing with a pathological liar in a relationship, a polygraph test in a therapeutic setting can be a valuable tool for establishing truth and beginning the healing process.

The Challenge of Diminished Physiological Responses

The central question for polygraph professionals is whether the physiological changes that underpin lie detection still occur when the subject is a pathological liar. Standard polygraph testing measures changes in heart rate, blood pressure, respiration, and electrodermal activity — all manifestations of the autonomic nervous system's response to the stress of deception.

For most people, telling a significant lie triggers the sympathetic nervous system's fight-or-flight response, producing readily detectable physiological changes. Pathological liars, however, present a unique challenge for several reasons:

Their increased prefrontal white matter may allow them to construct and maintain lies with less cognitive effort [2]Verified Prefrontal white matter in pathological liars
Confirms pathological liars show 22–26% increase in prefrontal white matter and 36–42% reduction in grey/white matter ratio. The amygdala desensitisation documented in research means their emotional response to lying may be blunted [5]Verified The brain adapts to dishonesty
Confirms amygdala response to lying declines with repeated dishonesty and larger drops predict bigger future lies. Some pathological liars may genuinely believe elements of their fabrications, reducing the conscious awareness of deception that normally triggers autonomic responses.

However, it is important to note that diminished does not mean absent. Even pathological liars retain physiological responses — they are simply subtler and require more sophisticated interpretation by the examiner.

Why Skilled Examiners Still Succeed

While instrumentation alone may not catch every pathological liar, the combination of physiological monitoring and skilled behavioural analysis significantly increases detection rates. Research demonstrates the power of examiner expertise: a study by Porter found that overall detection accuracy increased significantly from 46.4% to 80.9% following a single comprehensive, empirically based training workshop [3]Verified Catching liars: Training mental health and legal professionals to detect high-stakes lies
Confirms detection accuracy increased from 46.4% to 80.9% following comprehensive training.

Additionally, research on questioning techniques provides powerful tools. A study on unanticipated questions found that asking unexpected questions — especially spatial or visual requests — enabled correct classification of up to 80% of liar and truth-teller pairs, compared to chance-level accuracy on anticipated questions [4]Verified Outsmarting the liars: The benefit of asking unanticipated questions
Confirms unanticipated questions enabled correct classification of up to 80% of liar and truth-teller pairs. This is particularly relevant for pathological liars, who often prepare elaborate rehearsed narratives.

Research has also shown that liars overwhelmingly choose to base their deceptive reports on previously experienced events — 67% in one study and 86% in another — making their rehearsed details detectable through strategic questioning [21]Verified Exploring liars' strategies for creating deceptive reports
Confirms liars overwhelmingly base deceptive reports on previously experienced events (67–86%). Combined with findings that liars in collusion are actually more consistent between themselves than truth-telling pairs [22]Verified Partners in crime: How liars in collusion betray themselves
Confirms lying pairs are more consistent between themselves while truth tellers make more commissions of new information, skilled examiners have multiple analytical tools at their disposal beyond physiological measurement alone.

How the Autonomic Nervous System Responds to Deception

Polygraph testing fundamentally relies on the autonomic nervous system's response to the stress of deception. When an ordinary person lies about something significant, the sympathetic nervous system activates, releasing cortisol and adrenaline. This produces measurable changes: increased heart rate, elevated blood pressure, altered respiration patterns, and increased skin conductance through sweat gland activation.

For the average person, this response is involuntary and largely uncontrollable. The body treats lying as a form of threat, activating the same neural pathways that evolved to respond to physical danger. This makes the polygraph a powerful tool for the vast majority of the population.

The challenge with pathological liars is that their brain structure may partially buffer these responses. The 2016 Nature Neuroscience study demonstrated that repeated lying causes amygdala desensitisation — the emotional alarm system literally becomes quieter with practice [5]Verified The brain adapts to dishonesty
Confirms amygdala response to lying declines with repeated dishonesty and larger drops predict bigger future lies. For someone who has been lying extensively for years, as pathological liars typically have, this desensitisation may be quite advanced.

Why the Response Is Diminished, Not Eliminated

A critical point often overlooked in discussions about pathological liars and polygraphs is that autonomic responses are diminished, not eliminated. Even the most practised pathological liar retains physiological responses to certain types of questions and confrontational scenarios. The key lies in the examiner's ability to:

Design questions that bypass rehearsed narratives and tap into genuine emotional responses. Use the pre-test interview phase to establish behavioural baselines specific to the individual. Employ acquaintance tests to calibrate the instrument to the subject's unique physiological profile. Apply unanticipated questioning techniques that research shows can classify up to 80% of liars correctly [4]Verified Outsmarting the liars: The benefit of asking unanticipated questions
Confirms unanticipated questions enabled correct classification of up to 80% of liar and truth-teller pairs.

This is why the choice of examiner matters enormously when testing a suspected pathological liar. A veteran examiner with extensive experience in behavioural analysis and advanced questioning techniques will achieve far better results than standard protocol alone.

Beyond the Instrument: Behavioural Analysis

A polygraph examination is far more than wires and sensors — the examiner is the most important component of the process. Experienced examiners are trained to observe a comprehensive range of behavioural cues that complement the physiological data captured by the instrument.

Research has consistently shown that training dramatically improves detection rates. Porter's study demonstrated that detection accuracy nearly doubled — from 46.4% to 80.9% — after comprehensive training in empirically based deception detection methods [3]Verified Catching liars: Training mental health and legal professionals to detect high-stakes lies
Confirms detection accuracy increased from 46.4% to 80.9% following comprehensive training. This underscores that expertise, not just equipment, drives accurate results.

Skilled examiners pay close attention to verbal indicators such as unnecessary qualifiers, over-elaborate explanations, inconsistencies between accounts given at different points in the examination, and the level of verifiable detail provided. Research confirms that liars include fewer verifiable details than truth tellers, and this metric alone achieved 79% classification accuracy [7]Verified Exploiting liars' verbal strategies by examining the verifiability of details
Confirms liars include fewer verifiable details and that verifiable detail classification alone achieved 79% accuracy.

Strategic Questioning Techniques

One of the most effective tools against pathological liars is the use of unanticipated questions. Research by Fisher and colleagues found that anticipated questions produced chance-level accuracy in distinguishing liars from truth tellers, while unanticipated questions — especially requests to recall spatial or visual details — dramatically improved correct classification rates to 80% [4]Verified Outsmarting the liars: The benefit of asking unanticipated questions
Confirms unanticipated questions enabled correct classification of up to 80% of liar and truth-teller pairs.

Pathological liars typically prepare and rehearse their deceptive narratives extensively. By introducing questions they could not have anticipated, examiners force them to generate responses in real time rather than retrieving rehearsed scripts. This spontaneous cognitive demand is more likely to produce the physiological signatures that polygraph instruments detect.

The importance of using only qualified, experienced examiners cannot be overstated, particularly in cases involving suspected pathological liars. Using an unlicensed polygraph examiner could compromise the entire examination. For the best results, ensure your examiner has extensive experience with challenging subjects. Book a polygraph test with our experienced team.

What Trained Observers Notice

Beyond the polygraph instrument itself, there are numerous behavioural cues that skilled professionals observe during an examination. While popular culture often focuses on obvious "tells" like averted gaze or fidgeting, the reality is more nuanced.

Research on listening carefully to liars has revealed that verbal content analysis can be a powerful detection tool [23]Verified Catching liars by listening carefully
Foundational research relevant to verbal deception detection methods. Truth tellers tend to provide more spontaneous corrections and admit gaps in their memory, while liars present smoother, more polished narratives. Truth tellers also make more "commissions" — adding new information in subsequent retellings — while liars tend to stick rigidly to their rehearsed script [22]Verified Partners in crime: How liars in collusion betray themselves
Confirms lying pairs are more consistent between themselves while truth tellers make more commissions of new information.

For those dealing with deceptive behaviour outside a formal polygraph setting, understanding these patterns can help in everyday situations. If you suspect gaslighting in a relationship, a professional polygraph examination can provide clarity. Similarly, those dealing with denial about addiction or substance abuse in the home may find polygraph testing a valuable tool for establishing the truth.

A Powerful Tool in Expert Hands

The relationship between pathological liars and polygraph testing is not the simple binary that popular culture suggests. While pathological liars present genuine challenges due to their altered brain structure and diminished emotional responses to deception, modern polygraph testing — conducted by skilled, experienced examiners — remains a valuable and effective tool.

The evidence shows that: Standard physiological monitoring alone may produce less definitive results with pathological liars than with typical subjects. However, the combination of physiological measurement, strategic questioning, behavioural analysis, and examiner expertise creates a multi-layered detection system that pathological liars find extremely difficult to defeat. Research-backed techniques like unanticipated questions can correctly classify up to 80% of deceptive subjects [4]Verified Outsmarting the liars: The benefit of asking unanticipated questions
Confirms unanticipated questions enabled correct classification of up to 80% of liar and truth-teller pairs, and trained professionals achieve detection rates exceeding 80% [3]Verified Catching liars: Training mental health and legal professionals to detect high-stakes lies
Confirms detection accuracy increased from 46.4% to 80.9% following comprehensive training.

For individuals considering a polygraph test to address suspected pathological lying — whether in a relationship, family situation, or professional context — the key is selecting an examiner with specific experience in testing challenging subjects. The examiner's skill, training, and experience are the most important factors in achieving accurate results.

If you are wondering why someone who is lying would agree to a polygraph test, or if you are considering breaking free from patterns of habitual lying, professional support is available.

Honest Self-Reflection

If you are reading this article and wondering about your own lying patterns, that self-awareness is itself a significant indicator. Truly pathological liars rarely question their own behaviour in this way.

However, if you recognise some of the following patterns, it may be worth seeking professional support: You tell lies frequently, even when there is no clear reason to do so. Your lies tend to grow from an initial falsehood, creating increasingly complex situations. Your lying has caused impairment in your social relationships, work, or finances. You feel your lying is out of your control. You experience distress as a result of your lying behaviour.

Curtis and Hart developed a Survey of Pathological Lying (SPL) that assesses these very dimensions — impairment, distress, danger, lack of control, anxiety reduction through lying, escalation of lies, and purposelessness [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms prevalence of pathological lying at 8–13%, establishes diagnostic criteria, and reports pathological liars tell an average of 10 lies per day. If these patterns resonate with you, speaking with a mental health professional can be an important first step. Cognitive-behavioural therapy and habit-reversal training are among the approaches that may help [19]Verified Pathological lying in teens is associated with executive function deficits
Confirms pathological lying in teenagers is associated with executive function deficits and that treatments may centre on executive functioning.

For those dealing with depression or other mental health challenges alongside deceptive behaviour, our guide on depression and polygraph testing provides additional relevant information.