yes, therapy helps!
Eysenck's Theory of Personality: the PEN model

Eysenck's Theory of Personality: the PEN model

January 25, 2022

One of the most important theorists of the study of personality is Hans Eysenck. A psychologist born in Germany, but who at age 18 settled in the United Kingdom where he grew professionally. He carried out many investigations, although he became famous for his personality theory .

His approach is framed within the trait theory, which assumes that behavior is determined by relatively stable attributes that are the fundamental units of one's personality, because they predispose a person to act in a certain way. This means that traits must be consistent across situations and over time, but may vary between individuals.

Eysenck and the individual differences

For Eysenck, individuals differ in their traits due to genetic differences, although he did not rule out environmental and situational influences on personality, such as family interactions in childhood. So that is based on a biopsychosocial approach in which these genetic and environmental factors determine behavior .

What the author proposes is that each person is born with a specific structure at the cerebral level, which causes discrepancies in psychophysiological activity and, therefore, causes the individual to develop differences in the psychological mechanism, determining a specific type of personality.

The personality according to Hans Eysenck

Hans Eysenck developed a theory based on the results of the factor analysis of the responses of some personality questionnaires. Factor analysis is a technique that reduces behavior to a series of factors that can be grouped together under a heading called dimension, since they share common attributes.

In conclusion, he identified three independent dimensions of personality that I will explain later: Neuroticism (N), Extraversion (E) and Psychoticism (P), what gets the name of PEN model .

This model aims to be explanatory and causal, since it determines the biological bases of these dimensions and confirms them experimentally.

The Eysenck studios

During the decade of the 40, Eysenck worked in the Psychiatric Hospital of Maudsley (London, United Kingdom). His job was to perform the initial evaluation of each patient before his disorder was diagnosed by a psychiatrist. In this job he compiled a battery of questions about the behavior, which he later applied to 700 soldiers who were being treated in the same hospital for their neurotic disorders.

After passing the questionnaires, he realized that there seemed to be a bond of union between the soldiers' responses , suggesting that there were personality traits that were being revealed.

The personality structure according to Eysenck

After the results of his research, Eysenck proposes a hierarchical model of personality in which behavior can be ordered four different levels. This is the order from the lowest level to the highest:

  • First level : At this level are the responses that can be observed once, and which may or may not be characteristic of the person (for example, experiences of daily life).
  • Second level : These are the usual answers, which often happen under similar contexts (for example, if a test is answered a second time, similar answers will be given).
  • Third level : They are the habitual acts that are ordered by traits (sociability, impulsiveness, vivacity, etc.).
  • Fourth level : This level is the most extensive in the sense of generality, and there are the superfactors that I mentioned before: Neuroticism, Extraversion and Psychoticism.

People can score high or low on these superfactors. A low score in Neuroticism refers to high emotional stability. Low scores in Extraversion refer to Introversion.

The three types or superfactors are sufficient to describe the personality adequately, since predictions can be made from them both physiologically (for example, level of cortical activation), psychological (for example, level of performance) and social ( for example, criminal behavior).

The dimensions of the Eysenck Model

Neuroticism (stability-emotional instability)

People with emotional instability They show anxiety, hysteria and obsession. They often tend to react emotionally exaggeratedly and have difficulty returning to a normal state after emotional activation. At the other extreme, the person is calm, calm and with a high degree of emotional control.

Extraversion (extraversion-introversion)

The extraverts are characterized by sociability, impulsiveness, disinhibition, vitality, optimism and sharpness of wit; while introverts are calm, passive, unsociable, attentive, reserved, reflective, pessimistic and calm. Eysenck thinks that The main difference between extraverts and introverts lies in the level of cortical arousal .


People with high scores in psychoticism They are characterized by being insensitive, inhuman, antisocial, violent, aggressive and extravagant. These high scores are related to different mental disorders, such as the propensity to psychosis. In contrast to the other two dimensions, psychoticism does not have a reverse extreme, but is a component present at different levels in the person.

Biological bases of the PEN model: causal aspects

Taking into account this descriptive model of personality, the PEN model also provides a causal explanation. For this, it focuses on the biological, hormonal and psychophysiological mechanisms responsible for the three dimensions, in order to test this theory experimentally.

Theory of Cortical Activation and its relationship with extraversion

The theory of cortical activation appears later to another proposal of Eysenck himself, the Excitation-Inhibition model, since the latter did not allow making empirically testable predictions.

Excitation-inhibition model

The model of excitation-inhibition proposes that extraverted people have weak arousal potentials and strong reactive inhibition . In contrast, introverts have strong excitatory potentials and weak reactive inhibition.

Theory of Cortical Activation

The cortical activation of Eysenck proposes a biological explanation of extraversion taking into account the system of ascending reticular activation (SARA). The activity of SARA stimulates the cerebral cortex, which, in turn, increases the level of cortical activation.

The level of cortical arousal can be measured through the conductance of the skin, brain waves or sweat. Taking into account the different levels of SARA activity, Introverts have higher levels of activity than extraverts . Some research has shown that extraverts seek external stimulation sources that cause them a higher level of stimulation.

Neuroticism and activation of the limbic system

Eysenck also explains neuroticism in terms of activation thresholds of the sympathetic nervous system or the visceral brain. The visceral brain is also known as the limbic system, which consists of the hippocampus, amygdala, septum, and hypothalamus, and regulates emotional states such as sex, fear, and aggression. It is responsible for the fight or flight response in the face of danger.

The heart rate, blood pressure, skin conductance, sweating, respiratory rate and muscle tension (especially in the forehead) can be used to measure visceral brain activation levels. The neurotic people have low thresholds of visceral brain activation and are unable to inhibit or control their emotional reactions. Therefore, they experience negative effects in stressful situations, they are upset even in situations with less stress and they get upset very easily.

Psychoticism and gonadal hormones

Eysenck also provides biological explanation of psychoticism, specifically gonadal hormones such as testosterone and enzymes such as monoamine oxidase (MAO). Although there is not much research on psychoticism compared to extraversion and neuroticism, some current studies show that people with psychotic episodes have high testosterone levels and low levels of MAO.

In addition, in these studies, impulsivity and aggressiveness, two characteristic features of individuals who score high in psychoticism, correlated negatively with MAO, as this enzyme plays a key role in the degradation of monoamines noradrenaline, dopamine and serotonin. In those studies, It was also shown that low levels of MAO is a characteristic of psychotic patients .

Eysenck personality questionnaires

Following Eysenck's theory of personality, several questionnaires have emerged that are the result of more than forty years of development and a large number of psychometric and experimental studies carried out in many countries.

  • Maudsley Medical Questionnaire (MMQ): Contains 40 items and evaluates Neuroticism.
  • Maudsley Personality Inventory (MPI): Contains 48 items and evaluates Extraversion and Neuroticism.
  • Eysenck Personality Inventory (EPI): Contains 57 items and evaluates Neuroticism and Extraversion
  • Eysenck Personality Questionnaire (EPQ): Contains 90 items and evaluates the three superfactors: Extraversion, Neuroticism and Psychoticism.
  • Revised Eysenck Personality Questionnaire (EPQ-R): Contains 100 items and evaluates the three superfactors.

Bibliographic references:

  • Eysenck, H.J. and Eysenck, S.B.G. (1994). Manual of the Eysenck Personality Questionnaire. California: EdITS / Educational and Industrial Testing Service.
  • Gray, J. A. (1994). Three fundamental emotion systems. In P. Ekman & R. Davidson (Eds.). The nature of emotion (pp. 243-247). New York: Oxford University Press. Gutiérrez Maldonado, J. (1997). Psychology of the personality and experimental synthesis of behavior. Revista Latinoamericana de Psicología, 29, 435-457.
  • Pueyo, A. A. (1997). Manual of Differential Psychology. Madrid: Mc Graw Hill.
  • Schmidt, V., Firpo, L., Vion, D., Costa Oliván, M.E., Casella, L., Cuenya, L, Blum, G.D., and Pedrón, V. (2010). Psychobiological Personality Model of Eysenck: a history projected towards the future. International Journal of Psychology, 11, 1-21.

Eysenck's personality theory (January 2022).

Similar Articles