Hans Eysenck

Hans Jürgen Eysenck

Hans Jürgen Eysenck (March 4, 1916 – September 4, 1997) was a German-British psychologist who spent most of his career in Britain, best remembered for his work on intelligence and personality, though he worked in a wide range of areas. At the time of his death, Eysenck was the living psychologist most frequently cited in science journals.

Eysenck and the genetics of personality

In 1951, Eysenck’s first empirical study into the genetics of personality was published. It was an investigation carried out with his student and associate Donald Prell, from 1948 to 1951, in which identical (monozygotic) and fraternal (dizygotic) twins, ages 11 and 12, were tested for neuroticism. It is described in detail in an article published in the Journal of Mental Science. Eysenck and Prell concluded: “that the factor of neuroticism is not a statistical artifact, but constitutes a biological unit which is inherited as a whole….neurotic predisposition is to a large extent hereditarily determined.”

Eysenck’s model of personality (P–E–N)

The two personality dimensions, Extraversion and Neuroticism, were described in his 1947 book Dimensions of Personality. It is common practice in personality psychology to refer to the dimensions by the first letters, E and N.

E and N provided a 2-dimensional space to describe individual differences in behaviour. An analogy can be made to how latitude and longitude describe a point on the face of the earth. Also, Eysenck noted how these two dimensions were similar to the four personality types first proposed by the Greek physician Hippocrates.

High N and High E = Choleric type
High N and Low E = Melancholic type
Low N and High E = Sanguine type
Low N and Low E = Phlegmatic type

The third dimension, psychoticism, was added to the model in the late 1970s, based upon collaborations between Eysenck and his wife, Sybil B. G. Eysenck, who is the current editor of Personality and Individual Differences.

The major strength of Eysenck’s model was to provide detailed theory of the causes of personality. For example, Eysenck proposed that extraversion was caused by variability in cortical arousal: “introverts are characterized by higher levels of activity than extraverts and so are chronically more cortically aroused than extraverts”. While it seems counterintuitive to suppose that introverts are more aroused than extraverts, the putative effect this has on behaviour is such that the introvert seeks lower levels of stimulation. Conversely, the extravert seeks to heighten his or her arousal to a more favorable level (as predicted by the Yerkes-Dodson Law) by increased activity, social engagement and other stimulation-seeking behaviors.

Comparison with other theories

The major alternative to Eysenck’s three-factor model of personality is a model that makes use of five broad traits, often called the Big Five model (see big five personality traits) (Costa & McCrae, 1985). The traits in the Big Five are as follows:

• Openness to experience
• Conscientiousness
• Extraversion
• Agreeableness
• Neuroticism

Extraversion and Neuroticism in the Big Five are similar to Eysenck’s traits of the same name. However, what Eysenck calls the trait of Psychoticism corresponds to two traits in the Big Five model: Conscientiousness and Agreeableness. Eysenck’s personality system did not address Openness to experience. He argued that his approach was a better description of personality (Eysenck, 1992a; 1992b).

Another important model of personality is that of Jeffrey Alan Gray, a former student of his.

Psychometric scales relevant to Eysenck’s theory

Eysenck’s theory of personality is closely linked with the scales that he and his co-workers developed. These include the Maudsley Medical Questionnaire, Eysenck Personality Inventory (EPI), Eysenck Personality Questionnaire (EPQ) and Sensation Seeking Scale (developed in conjunction with Marvin Zuckerman). The Eysenck Personality Profiler (EPP) breaks down different facets of each trait considered in the model. There has been some debate about whether these facets should include impulsivity as a facet of extraversion as Eysenck declared in his early work; or psychoticism. Eysenck declared for the latter, in later work.

Eysenck’s later work

In 1994 he was one of 52 signatories on “Mainstream Science on Intelligence,” an editorial written by Linda Gottfredson and published in the Wall Street Journal, which declared the consensus of the signing scholars on issues related to race and intelligence following the publication of the book The Bell Curve. Gottfredson described the drafting of the statements on intelligence and process of gathering signatures on that document in a 1997 editorial in the journal Intelligence. Eysenck includes the entire text of the 1994 editorial (including the lead paragraphs mentioning the book The Bell Curve and twenty-five propositions about human intelligence) in his 1998 book Intelligence: A New Look, saying, “I did not find any particular discrepancies between my account” and the statements in that editorial.

Eysenck made early contributions to fields such as personality by express and explicit commitment to a very rigorous adherence to scientific methodology, as Eysenck believed that scientific methodology was required for progress in personality psychology. He used, for example, factor analysis, a statistical method, to support his personality model. An example is Inheritance of Neuroticism: An Experimental Study, quoted above. His early work showed Eysenck to be an especially strong critic of psychoanalysis as a form of therapy, preferring behaviour therapy. Despite this strongly scientific interest, Eysenck did not shy, in later work, from giving attention to parapsychology and astrology. Indeed, he believed that empirical evidence supported the existence of paranormal abilities.