Why Do Pathological Liars Keep Lying? Psychology Explained

What Defines a Pathological Liar?

Lying is a universal human behaviour. Research shows that people lie in approximately 25% of daily social interactions [10]Verified Lying in Everyday Life
Confirms people lie in approximately 25% of daily social interactions, establishing baseline deception frequency in normal populations, with most people telling relatively few lies — typically zero on any given day [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. These everyday lies are generally minor social lubricants that carry little consequence.

However, there exists a category of lying that transcends the ordinary. Pathological lying — clinically known as pseudologia phantastica — represents the most severe and persistent form of deceptive behaviour [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. A pathological liar doesn't simply bend the truth occasionally; they construct elaborate fabrications as a core component of their interactions with others.

What distinguishes pathological lying from normal dishonesty is its frequency, persistence, compulsiveness, and the distress and impairment it causes. Curtis and Hart (2020) defined pathological lying as a persistent, pervasive, and often compulsive pattern of excessive lying behaviour that leads to clinically significant impairment of functioning, causes marked distress, poses a risk to the self or others, and occurs for longer than six months [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. Research from their landmark study estimates the prevalence of pathological lying at 8–13% of the population [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria, though the authors note this may be slightly elevated due to recruitment methods [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Pathological liars in the study reported telling an average of 10 lies per day (with a mode of 1) [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria, and their lying had persisted for longer than six months — a duration consistent with diagnostic thresholds for other DSM-5 disorders [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. People who identified as pathological liars reported greater distress, impaired functioning, and more danger than those not considered pathological liars [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

A small group of just over 5% of the population tell half of all lies — these are classified as 'prolific liars' [2]Verified Have You Ever Met a Pathological Liar?
Confirms that approximately 5% of people are prolific liars telling half of all lies, and pathological liars tell 10+ lies per day with primarily self-serving lies. However, researchers emphasise that prolific lying and pathological lying are distinct: pathological liars experience their lying as compulsive, with lies growing from an initial lie and often done for no apparent reason [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. Understanding these distinctions is crucial for the fields of forensic psychology and polygraph examination, where accurately identifying deceptive individuals is essential.

From Pseudologia Phantastica to Modern Understanding

The formal study of pathological lying has deep roots in late 19th-century German psychiatry. Anton Delbrück (1862–1944), a German psychiatrist born in Halle/Saale, first described pseudologia phantastica in 1891 in his work 'Die pathologische Lüge und die psychisch abnormen Schwindler' [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation. He coined the term to describe patients who told lies so outrageous and persistent that the behaviour could only be explained by an underlying pathological condition [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation. The phenomenon was also described independently in 1890 by G. Stanley Hall, who published research on excessive lying in children [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Delbrück's observation was groundbreaking because it separated pathological lying from ordinary dishonesty. Prior to his work, excessive lying was generally viewed as a moral failing rather than a symptom of psychological dysfunction. By framing it as a clinical phenomenon, Delbrück opened the door to understanding that some people are compelled to lie by deeply rooted psychological conditions. The French psychiatrist Ernest Dupré further contributed to understanding by coining the alternative term 'mythomania' in 1905 [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation.

More than a century later, Healy and Healy (1926) produced a foundational forensic psychology study of pathological lying, examining 1,000 juvenile offenders and finding that 8–10 were genuine pathological liars showing 'falsification entirely disproportionate to any discernible end in view' [5]Verified Pathological Lying, Accusation, and Swindling: A Study in Forensic Psychology
Confirms among 1,000 juvenile offenders studied, 8-10 were genuine pathological liars showing excessive falsification disproportionate to any discernible goal, with gender differences documented. Their study documented important gender differences, with 26% of females versus 15% of males among the pathological liars they studied [5]Verified Pathological Lying, Accusation, and Swindling: A Study in Forensic Psychology
Confirms among 1,000 juvenile offenders studied, 8-10 were genuine pathological liars showing excessive falsification disproportionate to any discernible goal, with gender differences documented.

Pathological lying is not currently recognised as a standalone diagnosis in the DSM-5, though it appears as a feature of several recognised personality disorders [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. It is listed as a symptom within Antisocial Personality Disorder and Malingering. Curtis and Hart (2020) have argued persuasively that pathological lying should be established as its own diagnostic entity, and their research provides empirical support for this position [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. A follow-up study of 295 psychotherapists found that 52% believed pathological lying should be considered a diagnostic entity, and 74% reported having worked with a patient exhibiting pathological lying [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Antisocial Personality Disorder (ASPD)

Antisocial Personality Disorder is one of the most common psychological conditions underlying pathological lying. The DSM-5 lists 'deceitfulness, as indicated by repeated lying, use of aliases, or conning others for personal profit or pleasure' as a diagnostic criterion for ASPD [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. ASPD is characterised by a persistent disregard for the rights of others, lack of empathy, and a pattern of manipulative and exploitative behaviour.

Pathological lying is also an item on the Psychopathy Checklist-Revised (PCL-R), the gold-standard assessment for psychopathy, alongside superficial charm, grandiosity, and manipulativeness [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception. The PCL-R describes pathological lying as lying so frequent and central to an individual's interactions that it defines them — with lies told with ease even when contradicting facts are readily available [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception.

Individuals with ASPD who develop pathological lying tendencies often represent the most challenging category for detection. They typically lie for concrete objectives: financial gain, social status, sexual conquest, and emotional manipulation. Research by Hare, Forth, and Hart (1989) established the psychopath as the prototype for pathological lying and deception, finding a marked discrepancy between clinical manifestations of deception and laboratory measures [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception. Their research also suggested that polygraph examinations may detect psychopathic deception, contrary to popular assumption [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception.

For polygraph professionals, understanding ASPD and its relationship to deception is critical. Our guide on pathological liars and polygraph testing provides detailed examination protocols for these challenging cases.

Narcissistic Personality Disorder (NPD)

Narcissistic Personality Disorder is another major contributor to pathological lying. Individuals with NPD possess a grandiose sense of self-importance, a deep need for excessive admiration, and a pronounced lack of empathy for others. Their pathological lying serves multiple functions within their psychological architecture.

Narcissistic pathological liars fabricate stories to bolster their self-image, exaggerating accomplishments, connections, or abilities far beyond reality. They lie to manipulate others into providing constant validation. They lie to avoid accountability for mistakes or failures, as acknowledging imperfection threatens the fragile false self they've constructed. And they lie preemptively to control how others perceive them.

When confronted with evidence of their lies, narcissistic individuals often respond with rage, gaslighting, or elaborate counter-narratives designed to make the confronter doubt their own perceptions. Understanding how narcissistic personality disorder intersects with deception is valuable for anyone navigating these relationships. Our in-depth guide on the narcissistic liar explores warning signs and protective strategies.

Borderline Personality Disorder (BPD)

Borderline Personality Disorder presents a distinct motivation for pathological lying. Individuals with BPD are characterised by intense fear of abandonment, unstable relationships, volatile emotions, and an uncertain sense of identity. Their pathological lying often develops as a defence mechanism against their core terror: being rejected or abandoned.

BPD-driven pathological liars may fabricate stories to keep partners or friends emotionally engaged. They may lie about their past, feelings, or actions to present a version of themselves they believe will be more acceptable or lovable. They may create crises — including false accusations — to test whether people will stay or leave. The lying is less about strategic manipulation and more about desperate attempts to prevent abandonment.

This makes BPD-related pathological lying qualitatively different from ASPD-related deception. The motivation is attachment-based rather than exploitation-based, which has important implications for treatment approaches and polygraph examination protocols.

Additional Conditions Associated with Pathological Lying

Several other conditions are commonly associated with pathological lying:

Substance Use and Impulse Control Disorders: Individuals struggling with addiction frequently develop elaborate deceptive frameworks to conceal their substance use. Over time, these lies can become so pervasive they take on characteristics of pathological lying. Our guide on polygraph testing in addiction recovery programs explores how lie detection is used in treatment settings.

Factitious Disorder (Munchausen Syndrome): Individuals with this condition repeatedly fabricate or induce illness in themselves or those in their care. Their pathological lying is specifically focused on medical and health-related deception.

Frontotemporal Dementia: This neurodegenerative condition affects the temporal and frontal regions of the brain, which are responsible for language processing and behavioural control. Compulsive lying has been reported as a symptom of behavioural variant frontotemporal dementia, where the organic breakdown of neural systems disrupts honest communication [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex.

Obsessive-Compulsive Disorder: Individuals with OCD may develop lying patterns specifically to conceal their compulsions from others. OCD-related pathological lying tends to be more focused and specific than the broad-spectrum deception seen in ASPD or NPD.

How Early Life Experiences Shape Deceptive Patterns

Research consistently indicates that the onset of pathological lying most commonly occurs during adolescence [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. Curtis and Hart (2020) found that adults who were pathological liars indicated that the onset of their problematic lying behaviour was in adolescence [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. A study of 512 adolescent participants found evidence of pathological lying in 63 of them, who told an average of about 10 lies per day with impairment in functioning, greater distress, and increased danger [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. Executive functioning scores were significantly elevated in the pathological lying sample, indicating problems with attention, working memory, and impulse control [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Traumatic experiences during formative years — including physical abuse, emotional neglect, sexual abuse, and chronic household dysfunction — can fundamentally alter a child's relationship with truth and honesty. Children who experience abuse or neglect often discover that lying serves as a survival mechanism. They may develop what researchers describe as traumatic bonding with their abusers — a dynamic that shares similarities with Stockholm Syndrome, where victims develop emotional bonds with and protective instincts toward perpetrators [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation. Research has found that aspects of this bonding dynamic can be observed in adult survivors of child sexual abuse, where the emotional bond with the abuser has served to protect the offender long after the abuse has ceased [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation.

Alternatively, children in dysfunctional households may discover that fabrication is more effective than truth for getting basic needs met. They may also develop lying as an emotional coping mechanism — creating alternate realities where they are safe, loved, or powerful, as an escape from their actual circumstances.

The critical danger is that these childhood survival strategies become deeply encoded in the individual's personality structure. What began as a desperate coping mechanism in childhood solidifies into an automatic behavioural pattern during adolescence and crystallises into full-blown pathological lying in adulthood. For professionals working with adolescents showing early signs of pathological deception, our guide on dealing with a manipulative child addresses unique practical considerations.

The Twin Engines of Pathological Deception

Experts in the psychology of deception have identified two primary motivational categories driving pathological lying behaviour.

Material Gain: The first major motivator is tangible benefit. Pathological liars in this category lie to deceive others out of money, property, career opportunities, sexual access, or other material advantages. Their lies are investments — carefully crafted deceptions designed to yield concrete returns. The foundational forensic psychology study by Healy and Healy (1926) documented this pattern extensively in their examination of pathological liars who engaged in accusation and swindling [5]Verified Pathological Lying, Accusation, and Swindling: A Study in Forensic Psychology
Confirms among 1,000 juvenile offenders studied, 8-10 were genuine pathological liars showing excessive falsification disproportionate to any discernible goal, with gender differences documented.

Attention and Sympathy: The second motivator is social and emotional. These pathological liars construct elaborate stories designed to impress, captivate, or elicit sympathy from their audience. A defining characteristic of pseudologia phantastica is that stories are presented in a way that portrays the liar favourably — as the hero or the victim [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. They may claim relationships with famous people, describe heroic actions they never performed, or position themselves as victims of dramatic events.

Research by Hart and Curtis found that 100% of people who reported interacting with a pathological liar indicated the liar told primarily self-serving lies [2]Verified Have You Ever Met a Pathological Liar?
Confirms that approximately 5% of people are prolific liars telling half of all lies, and pathological liars tell 10+ lies per day with primarily self-serving lies. Nearly half of the lies told by pathological liars appeared to be told for no apparent reason [2]Verified Have You Ever Met a Pathological Liar?
Confirms that approximately 5% of people are prolific liars telling half of all lies, and pathological liars tell 10+ lies per day with primarily self-serving lies, suggesting an element of compulsivity beyond simple strategic calculation.

The Victim Narrative Strategy

One of the most common and insidious patterns among attention-seeking pathological liars is the construction of a victim narrative. These individuals fabricate stories in which they are the injured party — tales of abuse, kidnapping, assault, abandonment, or persecution.

These fabricated victim stories serve multiple purposes: they generate sympathy and emotional support, they provide a convenient explanation for shortcomings or failures, and they create a bond of protective loyalty among believers. The victim narrative is particularly effective because most people are psychologically inclined to believe and support someone who claims to have suffered — a dynamic that research on truth-default theory helps explain. Timothy Levine's (2022) truth-default theory identifies factors that affect acceptance of implausible false information, including own belief congruity, social congruence, and message repetition [6]Verified Truth-default theory and the psychology of lying and deception detection
Confirms three moderators affecting acceptance of false information: own belief congruity, social congruence, and message repetition. These factors explain why repeated victim narratives become increasingly believable to those who hear them.

For those who suspect they are dealing with fabricated narratives — particularly in the context of false accusations — professional assessment and, in some cases, polygraph examination may be appropriate tools for establishing the truth.

The Self-Reinforcing Cycle of Deception

One of the most common questions about pathological liars is simply: why don't they stop? The answer involves multiple reinforcing mechanisms that make the behaviour extremely difficult to break.

Perceived Benefit Exceeds Honest Alternatives: Pathological liars possess an acute awareness of the utility of their lies. They calculate that deception will achieve a specific goal more effectively than honest behaviour. Where most people see honest effort as sufficient, the pathological liar perceives lying as a superior strategy.

Minimal Perceived Risk of Detection: Normal people are deterred from lying primarily by fear of being caught. Research on deception detection consistently shows that most people — including professionals — are poor lie detectors. Vrij's (2000) comprehensive analysis found that popular beliefs about how liars behave are largely mistaken, with no single reliable behavioural cue to deception [8]Verified Detecting lies and deceit: The psychology of lying and implications for professional practice
Confirms certain verbal characteristics are more present in lies than honest accounts, but popular beliefs about how liars behave are largely mistaken. This means pathological liars are often correct in their assessment that they won't be caught through observation alone.

Neural Desensitisation: A landmark 2016 study published in Nature Neuroscience by researchers at UCL provided the first empirical evidence that lying escalates over time due to neural desensitisation [9]Verified The brain adapts to dishonesty (Amygdala desensitisation during lying)
Confirms amygdala response to lying declined with every lie while magnitude of lies escalated; larger drops in amygdala activity predicted bigger lies in future. The study found that the amygdala — the brain's emotional alarm centre — was most active when people first lied for personal gain, but its response declined with every subsequent lie while the magnitude of lies escalated [9]Verified The brain adapts to dishonesty (Amygdala desensitisation during lying)
Confirms amygdala response to lying declined with every lie while magnitude of lies escalated; larger drops in amygdala activity predicted bigger lies in future. Crucially, larger drops in amygdala activity predicted bigger lies in the future [9]Verified The brain adapts to dishonesty (Amygdala desensitisation during lying)
Confirms amygdala response to lying declined with every lie while magnitude of lies escalated; larger drops in amygdala activity predicted bigger lies in future.

Internal Moral Justification: Most people experience guilt and shame after lying — internal moral feedback that discourages future dishonesty. Pathological liars either don't experience these emotions at all (as in cases of ASPD with psychopathic features) or possess sophisticated mechanisms for neutralising them. Their lying is often reported as reducing anxiety rather than causing it, creating a feedback loop where deception becomes self-soothing [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Compulsive Elements: Curtis and Hart's research revealed that pathological lying contains significant elements of compulsiveness — with lies growing from an initial lie and the lying often experienced as out of the individual's control [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. This distinguishes pathological lying from purely strategic deception.

Brain Differences in Pathological Liars

Groundbreaking neuroimaging research has revealed measurable structural brain differences in pathological liars. Yang, Raine, and colleagues at the University of Southern California conducted the first structural brain imaging studies of deceitful individuals, published in the British Journal of Psychiatry.

Their initial 2005 study found that pathological liars showed a 22–26% increase in prefrontal white matter and a 36–42% reduction in prefrontal grey/white ratios compared with both antisocial controls and normal controls [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. A follow-up 2007 study localised these increases to specific prefrontal subregions: orbitofrontal cortex (22–26% increase), inferior frontal cortex (32–36% increase), and middle frontal cortex (28–32% increase) compared with both control groups [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex.

As lead researcher Adrian Raine explained, more white matter — the neural wiring that connects brain regions — may provide liars with enhanced cognitive tools for the complex art of deceit [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. Lying requires suppressing the truth, understanding another person's mindset, regulating one's own emotions to avoid appearing nervous, and maintaining a consistent narrative. Increased white matter networking in the prefrontal cortex gives pathological liars what amounts to a natural neurological advantage for these tasks [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex.

Critically, grey matter — the brain cells that help keep impulses in check — was reduced in pathological liars [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. This means they have more neural 'equipment' to lie coupled with fewer moral restraints than normal people [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. This neurological profile helps explain what happens to the body during deception and why pathological liars can appear so convincing.

A meta-analysis of 114 studies examining the cognitive demands of lying found a large standardised reaction time difference (d = 1.049) between lying and truthful responses [11]Verified Lying and Psychology
Confirms meta-analysis of 114 studies showing large standardised RT difference of d = 1.049 between lying and truthful responses, representing one of the most substantial effects in cognitive psychology. However, pathological liars may be faster at generating and telling lies than normal individuals, with more efficient cognitive networks for deception [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex.

Recognising Pathological Deception

Identifying a pathological liar requires awareness of several key behavioural patterns. Research suggests the following warning signs:

Excessive Lying Frequency: Pathological liars tell numerous lies each day — an average of about 10 according to research [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria, compared to the typical person's average of approximately two lies per day [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. The sheer volume of dishonesty is often the first clue.

Lies That Are Self-Aggrandising or Self-Victimising: Stories are consistently presented in a way that portrays the liar favourably — as the hero or the victim [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. They 'decorate their own person' by telling stories that present them as fantastically brave, as knowing or being related to famous people, or as having great power, position, or wealth [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex.

Lies Disproportionate to Any Discernible Goal: Many lies told by pathological liars appear purposeless — even self-incriminating or damaging [5]Verified Pathological Lying, Accusation, and Swindling: A Study in Forensic Psychology
Confirms among 1,000 juvenile offenders studied, 8-10 were genuine pathological liars showing excessive falsification disproportionate to any discernible goal, with gender differences documented. This is a distinguishing feature from normal strategic lying.

Compulsive Quality: The lying feels out of control. Curtis and Hart found that pathological liars reported their lying was out of their control and that lies tended to grow from an initial lie [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Chronicity: The behaviour has persisted for longer than six months, often years [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. Most psychotherapists reported their patients had been excessively lying for more than five years [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Impaired Functioning: The lying has caused significant problems in social relationships, occupation, finances, or legal contexts [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. The area of greatest impairment reported was in social relationships [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Distress: The individual experiences psychological distress from their lying, yet cannot stop [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

For a deeper understanding of how verbal deception patterns manifest, Vrij's research [8]Verified Detecting lies and deceit: The psychology of lying and implications for professional practice
Confirms certain verbal characteristics are more present in lies than honest accounts, but popular beliefs about how liars behave are largely mistaken documents that certain verbal characteristics — shorter responses, fewer self-references, and indirect replies — are more consistently present in lies than in honest accounts.

Understanding the Key Distinctions

While some mental health professionals use 'pathological liar' and 'compulsive liar' interchangeably, others see them as distinct categories [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. The debate remains an area of considerable controversy in the field.

The general distinction drawn by those who differentiate the two is that pathological liars may have clearer motivations — seeking attention, admiration, or material gain — while compulsive liars cannot control their lying and may lie even after being caught or exposed, sometimes without any discernible motive [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex.

Research by Curtis and Hart found that pathological lying contains elements of both strategic and compulsive deception [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. People classified as pathological liars reported that telling lies reduced their anxiety and that their lying was out of their control [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria — hallmarks of compulsivity. Yet the lies also tend to serve identifiable self-serving purposes [2]Verified Have You Ever Met a Pathological Liar?
Confirms that approximately 5% of people are prolific liars telling half of all lies, and pathological liars tell 10+ lies per day with primarily self-serving lies.

The Psychopathy Checklist-Revised (PCL-R) makes a useful practical distinction: it separates pathological lying (lying as a defining characteristic of interactions) from manipulation (the strategic use of deceit for personal gain) [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. Understanding this distinction matters for professionals — including polygraph examiners — who need to assess the nature and purpose of an individual's deception.

The Blurred Line Between Fiction and Reality

The debate over whether pathological liars recognise their lies as false has occupied researchers for decades [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation. It has been observed that some pathological liars believe their lies to the extent that the belief may be delusional — leading early researchers to describe pathological lying as a 'wish psychosis' [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation.

Pathological lying has also been described as impulsive and unplanned, raising doubts about the pathological liar's ability to fully control their behaviour [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation. The relative purposelessness of many lies, including the intangible benefits of false accusations or self-incrimination, and the repetitive nature of the lies despite negative consequences, further support the notion that conscious control may be limited [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation.

People who engage in pathological lying often report being unaware of the motivations for their lies [4]Verified Localisation of increased prefrontal white matter in pathological liars
Confirms pathological liars showed 22–26% white matter increase in orbitofrontal cortex, 32–36% in inferior frontal cortex, and 28–32% in middle frontal cortex. This ambiguous awareness — somewhere between fully conscious deception and genuine self-delusion — is a core feature that distinguishes pathological lying from ordinary dishonesty.

This has important implications for polygraph testing. If a pathological liar genuinely believes their own fabrications, the physiological indicators of deception — which rely on the cognitive conflict between truth and lie — may be attenuated. Understanding this dynamic is essential for polygraph examiners working with these complex cases. Learn more about detection challenges in our guide to false negatives in polygraph testing.

Can Lie Detectors Catch Pathological Liars?

A common misconception is that pathological liars — particularly those with psychopathic traits — can easily defeat polygraph examinations. The scientific evidence tells a more nuanced and encouraging story.

Research by Raskin and Hare found that psychopaths who committed a mock crime were detected by the control question test at a rate of 95.8% — actually slightly higher than non-psychopaths at 95% [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception. Not a single participant, psychopath or otherwise, was able to produce a false negative result in their study. When polygraph charts were analysed, psychopaths actually exhibited stronger electrodermal responses and greater heart rate deceleration when lying than non-psychopaths [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception.

A subsequent study by Patrick and Iacono (1989) confirmed that guilty psychopaths were detected just as easily as guilty non-psychopaths, with 87% of guilty subjects correctly identified when excluding inconclusives [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception. As the Journal of the American Academy of Psychiatry and the Law notes, available evidence indicates that psychopaths respond to polygraph testing in a similar manner to other individuals [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception.

The explanation for this counterintuitive finding is that polygraph tests measure involuntary physiological changes governed by the autonomic nervous system. Even individuals who lack guilt or empathy still experience fear of detection and its consequences, which triggers measurable autonomic responses [7]Verified The Psychopath as Prototype for Pathological Lying and Deception
Confirms marked discrepancy between clinical manifestations of deception by psychopaths and empirical findings, with evidence suggesting polygraph examinations may detect psychopathic deception.

However, polygraph examiners should be aware of potential challenges when testing pathological liars. A meta-analysis of the psychology and lie detector industry spanning 50 years notes the importance of understanding how different psychological profiles can influence test outcomes [12]Verified Psychology and the Lie Detector Industry: A Fifty-Year Perspective
Comprehensive 50-year retrospective on polygraph science, reviewing evolution of CQT, CIT, and screening tests. Skilled examiners use comprehensive pre-test interviews and validated test protocols to ensure accuracy. Our guide on why guilty people take lie detector tests explores the psychological dynamics at play during polygraph examinations.

Therapeutic Approaches to Pathological Lying

No medication exists specifically for pathological lying [3]Verified Pathological Lying: Symptom or Disease?
Confirms Delbrück coined pseudologia phantastica in 1891, documents debate about self-awareness in pathological liars, and describes the 'wish psychosis' characterisation. Treatment is complicated by the central paradox of the condition: the patient's primary symptom is deception, which inherently undermines the therapeutic relationship.

In a study of 295 psychotherapists, 73% suggested cognitive-behavioural therapy (CBT) as part of treatment for pathological lying, with 41% recommending CBT alone [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. Other suggested approaches included dialectical behavioural therapy (12%), behavioural therapy (7%), acceptance and commitment therapy (4%), emotion-focused therapy (2%), and motivational interviewing (1%) [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Most psychotherapists reported that their patients had been excessively lying for more than five years before entering treatment [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria, indicating the deeply entrenched nature of the behaviour. Clinicians described these patients as lying with great frequency, with lying causing marked distress and impaired functioning across social, occupational, financial, and legal domains [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria.

Treatment success depends heavily on addressing the underlying condition driving the pathological lying — whether that is ASPD, NPD, BPD, or another disorder. Without treating the root cause, efforts to address lying behaviour alone are unlikely to succeed.

For individuals dealing with the emotional impact of a pathological liar in their life, our guide on seeking support when dealing with continuous lying provides practical steps for emotional well-being. Polygraph testing can also play a supportive role in treatment settings, particularly for addiction recovery programs and sexual addiction disclosure where accountability is a key component of rehabilitation.

Research-Based Questions to Consider

Curtis and Hart developed a Survey of Pathological Lying (SPL) to help identify pathological lying behaviour [1]Verified Pathological Lying: Theoretical and Empirical Support for a Diagnostic Entity
Confirms pathological lying prevalence of 8–13%, average of 10 lies per day, 6+ month duration threshold, and provides proposed diagnostic criteria. Based on their research, the following questions can help with self-reflection:

1. Have your lying behaviours resulted in impairment in your occupation, social relationships, finances, or legal contexts? 2. Does your lying cause you significant distress? 3. Has your lying put yourself or others in danger? 4. Is your lying something that feels out of your control? 5. After you lie, do you feel less anxious? 6. Do your lies tend to grow larger from an initial lie? 7. Are most of your lies told for no particular reason?

If you answered 'yes' to several of these questions, it may be worth consulting a mental health professional. Remember that pathological lying is a condition that can be addressed with appropriate help — and acknowledging the problem is the essential first step.

For those who want objective assessment of their own or someone else's truthfulness, polygraph examination offers a scientifically grounded method for establishing whether deception is present. The history of polygraph devices shows how this technology has evolved to address precisely these types of complex deception scenarios.