Hans Eysenck: The Three Dimensions Of Personality

Hans Eysenck was one of the most controversial and prolific psychologists of the 20th century. At the time of his death in 1997, he was the most cited researcher in the field of psychology. In fact, he contributed significantly to the development of this discipline thanks to the publication of about 80 books and hundreds of articles. He also worked as an editor at an influential magazine, Personality and Individual Differences , of which he was the founder.

Born in Germany in 1916, due to his opposition to the Nazi party he was forced to flee, first to France and then to Great Britain, where in 1940 he was able to obtain a doctorate in psychology at the University of London. During the Second World War, Hans Eysenck worked as a psychiatrist at the Mill Hill Emergency Hospital. Instead, between 1945 and 1950 he worked as a psychologist at Maudsley Hospital. He later served as director of the psychology department at the Institute of Psychiatry at the University of London, a post he held until 1983.

Hans Eysenck developed a very convincing theory of personality as it focuses on concrete situations, easily identifiable in the daily reality of each individual. He argued that every individual inherits a nervous system that affects their ability to learn and adapt to their surroundings.

Nonetheless, his theories were widely criticized as according to some, Eysenck would have suggested that biological or genetic factors can influence an individual’s personality and his propensity to be involved in criminal activity.

The dimensions of personality according to Eysenck: The PEN model

Using factorial analysis to develop his theory, Hans Eysenck identified three constitutive personality traits: psychoticism, extroversion, and neuroticism (PEN). Each of these traits is characterized by a potential bipolarity, that is to say that each is opposed by an opposite trait:

• Extroversion vs Introversion
• Neuroticism vs Emotional Stability
• Psychoticism vs Self-control (added to the model in 1996)

Eysenck believed that behind the development of certain personality traits at the expense of others, there were biological factors, including cortical arousal and hormone levels, added to environmental factors such as behaviors learned through various forms of conditioning.

However, it seems appropriate to specify that Eysenck attributed a particular meaning to the word “psychoticism”. It does not refer to a state of mental illness, but to a series of asocial behaviors.

Before developing the PEN model, Eysenck distinguished only two dimensions of personality: extraversion-introversion and neuroticism-emotional stability.

Extrversion vs Introversion

People with a high level of extroversion are more likely to participate in social activities. They tend to be more sociable and are perfectly comfortable when in a group. In general, extroverted people like to be the center of attention and very often surround themselves with friends and acquaintances. The yardstick of extroversion ranges from a very high level (extroverted people) to very low (introverted people).

Introverted people, on the other hand, tend to be quieter, stay away from social gatherings and easily feel uncomfortable when dealing with strangers. They usually have a small circle of friends and enjoy contemplative activities.

Swiss psychoanalyst Carl Jung suggested that extroversion-introversion levels depend on the way an individual channels their psychic energy. According to Jung, extroverted people channel that energy outwards, towards others. In the case of introverted people, this energy is projected inward, which is why they prefer activities focused on the inward. (Jung, 1921)

However, according to Hans Eysenck, extroversion is linked  to cortical excitation and  the level of brain activity of individuals. Extroverted people in fact would be characterized by less cortical excitement, which leads them to seek external stimuli. On the contrary, given their great brain activity, introverted people are inclined to avoid too stimulating situations that would lead to a further increase in cortical arousal levels.

According to the Yerkes-Dodson law, cortical arousal levels can also affect an individual’s performance. This theory postulates that arousal and performance form a bell-shaped curve as performance decreases when the level of brain activity is too high or too low. (Yerkes and Dodson, 1908)

Neuroticism vs Emotional Stability

Hans Heysenck also proposed the existence of a second dimension, that of emotional stability, which is contrasted with emotional instability (also called neuroticism). People who exhibit a high level of neuroticism tend to suffer more from stress and anxiety. They give too much importance to relatively insignificant situations that end up causing them worries, moreover, they can hardly manage stressful situations.

The tendency to focus on the negative aspects of a situation rather than the positive ones can lead to the development of an overly pessimistic point of view. People who look at life from a negative perspective tend to develop feelings of jealousy and envy towards other people, who according to them live in a privileged situation.

Another characteristic of neurotic people is the tendency to perfectionism and constant dissatisfaction. Conversely , people with a low level of neuroticism generally enjoy  greater  emotional stability. Generally speaking, these are individuals who feel capable of coping with stressful events and who tend to set goals appropriate to their abilities . People who are not very neurotic are usually more tolerant to the mistakes of others and are able to remain calm even in delicate situations.

Psychoticism vs normality

Psychoticism was added to Eysenck’s model only in 1976, it is a further addition to his already robust theory of personality. This third dimension ranges from normality (low level of psychoticism) to actual psychoticism.

People with high levels of psychoticism are often reckless and are more likely to find themselves engaging in irresponsible behavior. Another characteristic is the tendency to violate social norms and take actions in the name of immediate gratification, regardless of the long-term consequences.

However, psychoticism also has positive aspects. In a 1993 study, Eysenck compared the scores obtained by participants on the Barron-Welsh Art Scale  with those obtained in the Eysenck Personality Questionnaire  and observed that people with a high level of psychoticism tended  to also have greater creative abilities.

Eysenck also suggested that psychoticism is also influenced by biological factors, as well as having a correlation with testosterone levels. According to the PEN model, high levels of psychoticism make the individual more difficult to condition, so these people will have more difficulty adjusting to the social norms that are learned through the use of rewards and punishments.

According to Eysenck, such people are more likely to commit criminal acts, insofar as they try to further their own interests by violating the rules of conduct to which others adhere. This association has led some scholars to harshly criticize his theory, which is believed to be the result of a deterministic vision of human behavior.

Criticism of Hans Eysenck’s theory

To test the extent to which genetics affects personality, some studies have been conducted on pairs of twins. However, these studies have generated conflicting and therefore inconclusive results.

Shields (1976) observed that monozygotic (identical) twins were significantly more similar in manifestation of introversion-extroversion and psychoticism traits than dizygotic (non-identical) twins. Loehlin, Willerman and Horn (1998) stated that only 50% of the variations in the levels of manifestation of various personality traits are due to hereditary factors. In light of this, it is clear that social factors are also quite relevant.

In any case,  Hans Eysenck must certainly be recognized for having considered both natural factors and the formation of the individual as determining factors. In fact, he argued that the biological predisposition to the development of certain personality traits, added to the influence and socialization to which we are subjected during childhood, condition our personality.

This interactionist perspective boasts greater validity than purely biological or environmental theories. Furthermore, such a perspective is easily adaptable to the diathesis-stress model according to which there is a biological predisposition that, combined with a triggering cause of an environmental nature, gives rise to certain behaviors.