One of the most important theorists in the study of personality is Hans Eysenck. A psychologist born in Germany, but at the age of 18 he settled in the United Kingdom where he grew professionally. He carried out many investigations, although he became famous for his personality theory
Its 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 should be consistent across situations and over time, but can vary between individuals.
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. Hence 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 brain 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.
Personality according to Hans Eysenck
Hans Eysenck developed a theory based on the results of factor analysis of the answers to 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 (Hey Psychoticism (P), what is called PEN model
This model aims to be explanatory and causal, since it determines the biological bases of these dimensions and confirms them experimentally.
Eysenck’s studies
During the 1940s, Eysenck worked at Maudsley Psychiatric Hospital (London, United Kingdom). His job was to perform the initial evaluation of each patient before their disorder was diagnosed by a psychiatrist. In this position he compiled a battery of behavioral questions, which he later applied to 700 soldiers who were being treated at the same hospital for their neurotic disorders.
After passing the questionnaires, He noticed that there seemed to be a link between the soldiers’ responses suggesting that there were personality traits that were being revealed.
The structure of personality according to Eysenck
Following the results of his research, Eysenck proposes a hierarchical model of personality in which behavior can be ordered into four different levels. This is the order from lowest to highest level:
People can score high or low on these superfactors. A low score in Neuroticism refers to high emotional stability. Low scores on Extraversion refer to Introversion.
The three types or superfactors are sufficient to describe personality adequately, since from these predictions can be made at both a physiological level (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 (emotional stability-instability)
People with emotional instability They show anxiety, hysteria and obsession. They often tend to overreact emotionally and have difficulty returning to a normal state after emotional activation. At the other extreme, the person is equanimous, calm and with a high degree of emotional control.
Extraverts are characterized by sociability, impulsiveness, disinhibition, vitality, optimism and sharp wit; while introverts are calm, passive, unsociable, attentive, reserved, reflective, pessimistic and calm. Eysenck thinks that The main difference between extraverts and introverts is in the level of cortical arousal
Psychoticism
People with high scores on psychoticism They are characterized by being insensitive, inhuman, antisocial, violent, aggressive and extravagant. These high scores are related to different mental disorders, such as a propensity for psychosis. In contrast to the other two dimensions, psychoticism does not have an inverse extreme, but is a component present at different levels in people.
Biological bases of the PEN model: causal aspects
Taking into account this descriptive model of personality, the PEN model also provides a causal explanation. To do this, it focuses on the biological, hormonal and psychophysiological mechanisms responsible for the three dimensions, in order to test this theory experimentally.
Cortical Activation Theory and its relationship with extraversion
The theory of cortical activation appears after another proposal by Eysenck himself, the Excitation-Inhibition modelsince the latter did not allow empirically testable predictions to be made.
Excitation-inhibition model
The excitation-inhibition model proposes that extraverted people have weak excitation potentials and strong reactive inhibition In contrast, introverted people have strong excitatory potentials and weak reactive inhibition.
Cortical Activation Theory
Eysenck’s cortical activation proposes a biological explanation of extraversion taking into account the ascending reticular activation system (SARA). SARA activity stimulates the cerebral cortex, which, in turn, increases the level of cortical activation.
The level of cortical arousal can be measured through skin conductance, 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 sources of external stimulation that cause a higher level of stimulation.
Eysenck also explains neuroticism in terms of the 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.
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 visceral brain activation thresholds and are unable to inhibit or control their emotional reactions. Therefore, they experience negative effects in stressful situations, are upset even in situations with lower tension, and become upset very easily.
Psychoticism and gonadal hormones
Eysenck also provides a biological explanation of psychoticism, specifically gonadal hormones such as testosterone and enzymes such as monoamine oxidase (MAO). Although there is not a lot of research on psychoticism compared to extraversion and neuroticism, some current studies show that people with psychotic episodes have high levels of testosterone and low levels of MAO.
Furthermore, in these studies, impulsivity and aggressiveness, two characteristic traits of individuals who score high in psychoticism, correlated negatively with MAO, since this enzyme plays a fundamental role in the degradation of the monoamines norepinephrine, dopamine and serotonin. In these studies, It was also shown that low MAO levels are a characteristic of psychotic patients
Eysenck Personality Questionnaires
As a result of Eysenck’s personality theory, 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.
