Eysenck Personality Questionnaire

1. Abstract

The Eysenck Personality Questionnaire (EPQ) represents one of the most empirically investigated and theoretically grounded psychometric self-report inventories in individual differences psychology. Developed by Hans J. Eysenck and Sybil B. G. Eysenck as an extension and refinement of the earlier Maudsley Personality Inventory (MPI) and Eysenck Personality Inventory (EPI), the classic EPQ comprises 90 items evaluated using a forced-choice dichotomous response format (Yes/No). The instrument operationalizes Hans Eysenck’s dimensional PEN model of personality, assessing three major biologically rooted superfactors: Psychoticism (P; 25 items), Extraversion (E; 21 items), and Neuroticism (N; 23 items), supplemented by an integral Lie scale (L; 21 items) intended to detect social desirability response sets and dissimulation. Psychometric evaluations across diverse international adult populations consistently demonstrate robust internal consistency, with typical Cronbach’s alpha coefficients ranging between 0.74 and 0.85 for Extraversion, 0.80 and 0.88 for Neuroticism, and 0.78 and 0.84 for the Lie scale, while Psychoticism demonstrates somewhat lower yet acceptable reliabilities ranging from 0.68 to 0.76 due to the marked skewness and multidimensionality of tough-minded traits. Extensive exploratory and confirmatory factor analyses confirm a replicable four-factor structural topology across cross-cultural samples, establishing profound convergent and discriminant validity with neurobiological, behavioral, psychiatric, and cognitive criteria. This article provides an exhaustive academic overview of the EPQ’s foundational theory, psychometric properties, structural architecture, clinical utility, scoring keys, and full authentic item inventory.

2. Keywords

Eysenck Personality Questionnaire, EPQ, PEN model, Extraversion, Neuroticism, Psychoticism, Lie scale, biological personality theory, psychometrics, trait theory, factor analysis, self-report inventory.

3. Authors

The Eysenck Personality Questionnaire was conceptualized, designed, and psychometrically standardized by Hans Jürgen Eysenck, PhD, DSc (1916–1997), Professor of Psychology at the Institute of Psychiatry, King’s College London, and Sybil Bianca Giulietta Eysenck, PhD (1927–2020), Senior Lecturer in Psychology at the Institute of Psychiatry, University of London, United Kingdom. Throughout the twentieth century, both researchers served as preeminent authorities in differential psychology, behavioral genetics, and experimental psychometrics, publishing seminal works on the biological substrates of temperamental variation. Subsequent cross-cultural adaptations and major revisions, including the Dutch adaptation, were spearheaded by clinical researchers such as Robbert Sanderman, PhD, Department of Health Psychology, University of Groningen, the Netherlands.

4. Purpose

The fundamental objective of the Eysenck Personality Questionnaire is to evaluate human personality across continuous, orthogonal, biologically based dimensions rather than discrete diagnostic typologies. Rooted in differential psychology and behavioral neuroscience, the EPQ provides researchers and clinicians with an objective, standardized metric to quantify trait individual differences that determine cognitive reactivity, affective susceptibility, and social behavioral patterns. By systematically capturing variations across the superfactors of Psychoticism, Extraversion, and Neuroticism, alongside a validity index, the questionnaire serves multiple research and applied functions across health psychology, clinical diagnostics, neuropsychology, organizational screening, and forensic evaluations.

In clinical and medical contexts, the EPQ enables practitioners to appraise psychological vulnerability, affective fragility, and interpersonal predisposition. High Neuroticism scores index hyper-reactivity of the autonomic nervous system, identifying individuals at elevated risk for affective disorders, generalized anxiety, panic, somatic preoccupation, and maladaptive stress coping. Psychoticism assessments provide critical utility in psychiatric and forensic settings, capturing nonconformity, hostility, impulsivity, sensation-seeking, and low empathy, which correlate with antisocial personality configurations, conduct disorders, substance misuse, and schizotypal vulnerability. Conversely, Extraversion metrics clarify an individual’s optimal hedonic tone, sociability, and sensation threshold, facilitating the tailoring of behavioral and psychotherapeutic interventions.

In epidemiological and psychobiological research, the EPQ functions as an indispensable measurement paradigm for investigating genetic heritability, psychophysiological correlates (such as electroencephalographic frequency bands, cortical evoked potentials, and autonomic reactivity), pharmacological responsiveness, and longitudinal behavioral outcomes. Furthermore, the embedded Lie scale provides crucial verification of protocol validity, alerting investigators to intentional distortion, unconscious positive self-presentation, or defensive dissimulation in high-stakes evaluative settings.

5. Psychological Construct

The EPQ measures four distinct psychological constructs that operate as continuous phenotypic dimensions within the general population:

Extraversion vs. Introversion (E)

Extraversion reflects the extent to which an individual is oriented outward toward the social and sensory environment versus inward toward subjective contemplation. High-scoring individuals (Extraverts) are characterized by sociability, talkativeness, vivacity, surgency, optimism, reward sensitivity, and an active preference for external stimulation and large gatherings. They tend to be adventurous, carefree, quick-tempered, and prone to acting on the spur of the moment. Conversely, low-scoring individuals (Introverts) are reserved, introspective, quiet, reflective, and cautious. They prefer solitary pursuits or small circles of familiar acquaintances, exhibit heightened behavioral inhibition, plan meticulously in advance, avoid sensory overstimulation, and keep emotional expressions tightly regulated.

Neuroticism vs. Emotional Stability (N)

Neuroticism operationalizes individual differences in emotional reactivity, affective lability, and autonomic arousal. Individuals with elevated Neuroticism scores display chronic emotional vulnerability, marked by frequent shifts in mood, persistent worry, tension, generalized anxiety, depressive preoccupation, and heightened irritability. They tend to exhibit catastrophic thinking, hyper-arousal to minor environmental stressors, enduring guilt, somatic complaints, and sleep disturbances, taking extended periods to recover baseline homeostasis following disruption. In contrast, emotionally stable individuals (low N) display affective resilience, calm composure, low somatic reactivity to stressors, minimal anxiety, and steady emotional modulation under demanding circumstances.

Psychoticism vs. Normality / Impulse Control (P)

Psychoticism measures a trait spectrum that encompasses nonconformity, tough-mindedness, interpersonal hostility, sensation seeking, and diminished empathy. A high P score does not necessarily denote clinical psychosis; rather, it indexes a vulnerability continuum predisposing individuals to cognitive eccentricity, schizotypy, social detachment, and impulsivity. High scorers are described as cold, aloof, impersonal, aggressive, egocentric, and lacking social conscience, often taking pleasure in aggressive practical jokes, mocking conventional societal norms, and exhibiting indifference to the suffering of humans or animals. Low P scorers exhibit empathy, warm interpersonal attachment, rule-abiding behavior, conventionality, high conscientiousness, cooperativeness, and social responsibility.

Lie Scale / Social Desirability (L)

The Lie scale was initially integrated to detect intentional faking-good, impression management, and defensive dissimulation. Composed of socially desirable but empirically improbable behavioral statements (e.g., claiming to never boast, always keep promises, or never tell a lie), the scale captures the degree to which respondents distort their self-reports toward social perfection. Beyond simple dissimulation, psychometric research suggests the Lie scale also measures a stable personality facet involving unreflective social conformity, conventionality, lack of psychological insight, and cognitive rigidity.

6. Theoretical Framework

The theoretical cornerstone of the EPQ is Hans Eysenck’s PEN model of personality, which posits that phenotypic personality structures emerge directly from physiological and neurological mechanisms governed by genetic inheritance. Diverging from purely lexical or psychoanalytic approaches, Eysenck argued that phenotypic traits must possess demonstrable biological substrates, evolutionary functions, and neuroanatomical loci.

Extraversion is theoretically grounded in the baseline tone of the ascending reticular activating system (ARAS) within the brainstem, which regulates cortical arousal. Eysenck hypothesized an inverse relationship: Introverts possess naturally high baseline levels of cortical arousal and therefore maintain an inhibitory bias toward excessive sensory inputs to avoid sensory overload. Extraverts exhibit chronically under-aroused cortices and consequently seek external sensory stimulation, social interaction, and high-intensity environments to achieve an optimal level of arousal (the Yerkes-Dodson Law and hedonic tone concept).

Neuroticism is conceptualized as originating from individual thresholds of excitability within the limbic system (or visceral brain), comprising the amygdala, hippocampus, cingulate cortex, and hypothalamus. Individuals high in Neuroticism possess a chronically hyper-responsive autonomic nervous system, precipitating rapid activation of the sympathetic division during mild stressors, elevated circulating catecholamines, and prolonged visceral arousal recovery times.

Psychoticism was hypothesized to be linked to polygenic factors influencing gonadal hormone levels (specifically testosterone and related androgens) and neurochemical regulatory enzymes such as monoamine oxidase (MAO) and dopamine pathways. Lower levels of platelet MAO and heightened dopaminergic transmission have been correlated with elevated P scores, manifesting behaviorally as disinhibition, reduced prefrontal impulse regulation, and altered latent inhibition.

7. Validity

The validity of the EPQ has been confirmed across thousands of international studies spanning clinical, occupational, educational, and neurobiological domains:

Construct and Factorial Validity

Confirmatory factor analytic investigations consistently support the four-factor orthogonal architecture of the EPQ across sex, age, and cultural cohorts. Large-scale cross-cultural investigations spanning over 34 countries (e.g., Eysenck & Eysenck, 1985; Sanderman et al., 1991) confirmed that the structural congruence coefficients for Extraversion, Neuroticism, and the Lie scale routinely exceed 0.95, reflecting robust factorial invariance across linguistic translations.

Convergent and Discriminant Validity

The EPQ scales display robust convergent associations with corresponding dimensions of contemporary personality inventories. Extraversion and Neuroticism correlate strongly (typically r = 0.70 to 0.82) with the Extraversion and Neuroticism domains of the NEO Personality Inventory (NEO-PI-R). Psychoticism correlates negatively with NEO-PI-R Agreeableness (r = -0.50 to -0.65) and Conscientiousness (r = -0.35 to -0.48), confirming that P encompasses a composite of tough-minded, unconscientious, and disinhibited traits. Discriminant validity is supported by near-zero intercorrelations among the P, E, and N superfactors in non-clinical normative groups, affirming their orthogonality.

Predictive and Criterion Validity

EPQ dimensions predict a broad spectrum of empirical criteria. High N scores prospectively forecast clinical vulnerability to major depressive episodes, generalized anxiety disorder, and chronic pain disability. Elevated P scores reliably discriminate forensic populations, institutionalized offenders, and substance-dependent cohorts from normative control samples, exhibiting elevated rates of recidivism, impulsivity, and psychopathy. Extraversion scores accurately predict occupational choice, communicative fluency, speeded motor performance, social reward seeking, and sociometric popularity.

8. Reliability

The classic 90-item EPQ exhibits robust psychometric reliability across diverse demographic strata:

Internal Consistency

Empirical evaluations using Cronbach’s alpha (coefficient α) in large normative adult cohorts demonstrate strong internal consistency for the primary scales:

• Extraversion (E, 21 items): α = 0.84 to 0.88 for males; α = 0.82 to 0.86 for females.
• Neuroticism (N, 23 items): α = 0.83 to 0.89 for males; α = 0.85 to 0.90 for females.
• Lie Scale (L, 21 items): α = 0.78 to 0.83 for males; α = 0.80 to 0.85 for females.
• Psychoticism (P, 25 items): α = 0.68 to 0.76 for males; α = 0.65 to 0.72 for females. (The lower alpha for P reflects its non-normal, positively skewed distribution in general community samples, as well as the conceptual breadth of items spanning sensation-seeking, hostility, and anti-social tendencies).

Test-Retest Stability

Temporal stability assessments reveal high test-retest reliability across diverse intervals. Over a 1-month to 6-month interval, test-retest coefficients consistently range from 0.80 to 0.92 for Extraversion and Neuroticism, 0.75 to 0.85 for the Lie scale, and 0.65 to 0.78 for Psychoticism. Longitudinal studies following participants across multiple years demonstrate enduring stability coefficients for the biological superfactors, corroborating their status as enduring genotypic temperaments.

9. Factor Analysis

The architectural foundation of the EPQ was established via rigorous exploratory factor analysis (EFA) utilizing principal axis factoring and principal component analysis with orthogonal (Varimax) rotation, based on the postulate that the foundational dimensions of personality operate independently.

Initial matrix decompositions of the 90 items consistently yield four dominant eigenvalues exceeding the Kaiser-Guttman criterion (λ > 1.0) and confirmed via Cattell’s scree test:

• Factor I (Neuroticism): Accounts for the largest single proportion of shared variance among clinical indicators, characterized by primary loadings (≥ 0.40) on items indexing affective volatility, unprovoked anxiety, feelings of guilt, and physical tension.
• Factor II (Extraversion): Accounts for substantial variance, saturated with high positive loadings on items assessing talkativeness, liveliness, preference for parties, and sociability, and negative loadings on quietness and social withdrawal.
• Factor III (Psychoticism): Manifests through loadings on items assessing unconcern for others, cruelty to animals/humans, taking dangerous drugs, and enjoying aggressive jokes.
• Factor IV (Lie Scale): Loads exclusively on items measuring flawless adherence to strict moral and social conventions.

Confirmatory factor analytic (CFA) studies modeling the 90 items into four distinct orthogonal latents have yielded acceptable to good model fit indices across international samples (e.g., Comparative Fit Index [CFI] > 0.90, Root Mean Square Error of Approximation [RMSEA] ≤ 0.05). Factor congruence coefficients (Burt-Tucker phi) across independent cross-cultural samples routinely exceed 0.95 for E, N, and L, and typically range between 0.88 and 0.94 for P, confirming structural invariance across sexes and diverse cultural translations.

10. Instrument / Measurement Tool

• Standard Name: Eysenck Personality Questionnaire (EPQ).
• Instrument Nature: Standardized self-report psychometric questionnaire.
• Target Population: Adults (aged 16 years and older). A separate junior version (Junior EPQ) is utilized for children and adolescents aged 7 to 15.
• Total Item Count: 90 items in the classic full-length form (expanded to 101 items in the revised EPQ-R).
• Item Formats: Concise, direct behavioral and dispositional interrogative statements.
• Response Scale: Forced-choice Dichotomous (Yes / No).
• Dimensional Breakdown:
  • Psychoticism (P): 25 items
  • Extraversion (E): 21 items
  • Neuroticism (N): 23 items
  • Lie Scale (L): 21 items
• Scoring Methodology: Each item matching the keyed response direction receives 1 point; non-keyed responses receive 0 points. Scale totals are computed via linear sum:
  • Psychoticism (P) (25 items):
    • Keyed ‘Yes’ (1 point): Items 22, 26, 30, 34, 46, 50, 66, 68, 75, 76, 81, 85, 89
    • Keyed ‘No’ (1 point): Items 2, 5, 7, 9, 12, 14, 18, 41, 54, 59, 64, 71
  • Extraversion (E) (21 items):
    • Keyed ‘Yes’ (1 point): Items 1, 6, 11, 16, 20, 28, 36, 40, 45, 51, 55, 58, 61, 63, 72, 78, 83, 88
    • Keyed ‘No’ (1 point): Items 24, 32, 48
  • Neuroticism (N) (23 items):
    • Keyed ‘Yes’ (1 point): Items 3, 8, 13, 17, 21, 25, 29, 33, 37, 39, 42, 44, 47, 52, 57, 62, 67, 70, 74, 79, 82, 86, 90 (all 23 items keyed ‘Yes’)
    • Keyed ‘No’: None
  • Lie Scale (L) (21 items):
    • Keyed ‘Yes’ (1 point): Items 19, 27, 38, 69, 77, 87
    • Keyed ‘No’ (1 point): Items 4, 10, 15, 23, 31, 35, 43, 49, 53, 56, 60, 65, 73, 80, 84
• Administration Time: Approximately 10 to 15 minutes.

11. Permissions & Fee and Test Year

The original Eysenck Personality Questionnaire was published in 1975 by Hodder & Stoughton Educational (London) and Educational and Industrial Testing Service (EdITS, San Diego, CA). The subsequent revised form (EPQ-R) was published in 1985, and its Dutch validation was released in 1991. The EPQ is a copyrighted psychological assessment instrument. While the item pool has been widely reproduced across peer-reviewed academic literature for scholarly investigation and dissertation research, formal clinical and commercial applications require authorization and purchase of official scoring forms and administration manuals through authorized psychometric publishing bodies (such as EdITS or Hogrefe). Standard commercial use entails associated licensing and per-protocol testing fees.

12. References

Barrett, P. T., Petrides, K. V., Eysenck, S. B. G., & Eysenck, H. J. (1998). The Eysenck Personality Questionnaire: An examination of the factorial similarity of P, E, N, and L across 34 countries. Personality and Individual Differences, 25(5), 805–819. https://doi.org/10.1016/S0191-8869(98)00026-9

Eysenck, H. J. (1967). The biological basis of personality. Charles C Thomas Publisher. https://doi.org/10.4324/9781315081823

Eysenck, H. J., & Eysenck, M. W. (1985). Personality and individual differences: A natural science approach. Plenum Press. https://doi.org/10.1007/978-1-4613-2413-3

Eysenck, H. J., & Eysenck, S. B. G. (1975). Manual of the Eysenck Personality Questionnaire (Junior and Adult). Hodder and Stoughton.

Eysenck, S. B. G., Eysenck, H. J., & Barrett, P. (1985). A revised version of the Psychoticism scale. Personality and Individual Differences, 6(1), 21–29. https://doi.org/10.1016/0191-8869(85)90026-1

Sanderman, R., Arrindell, W. A., Ranchor, A. V., Eysenck, H. J., & Eysenck, S. B. G. (1991). Het meten van persoonlijkheidskenmerken met de Eysenck Personality Questionnaire (EPQ): Een handleiding [Measuring personality traits with the Eysenck Personality Questionnaire (EPQ): A manual]. Noordelijk Centrum voor Gezondheidsvraagstukken, Rijksuniversiteit Groningen.

13. Items of the Scale