Hans Eysenck

Introduction

Hans Jürgen Eysenck (4 March 1916 – 4 September 1997) was a German-born British psychologist who made the scientific study of personality into a quantitative, biologically grounded discipline. Where Freud offered case histories and Cattell offered sixteen factors, Eysenck offered three: extraversion, neuroticism and, later, psychoticism — the PEN model. He insisted that these were not merely statistical conveniences but expressions of the nervous system, and he spent a career trying to tie them to measurable physiology. He was enormously productive — around eighty books and more than a thousand journal articles — and at his death was, by one count, the third most cited psychologist in the world. He was also the most aggressive critic psychoanalysis ever faced in Britain, and an early champion of behaviour therapy. His reputation has since been sharply revalued: dozens of his papers on personality and disease have been found unsafe, and his work on race and intelligence has been rejected by mainstream science.

Early Life and Education

Eysenck was born in Berlin to Helga Molander, a Silesian-born film actress, and Eduard Anton Eysenck, a nightclub entertainer. His parents divorced and he was raised largely by his maternal grandmother, a Jewish convert to Catholicism who was deported under the Nuremberg laws and died in a concentration camp. He left Germany in 1934 after refusing to join the Nazi party, and the move became permanent. Because he was German he had difficulty finding work in Britain and was briefly at risk of internment during the war — an experience that left him, by his own account, with a lasting suspicion of collective authority.

He first read physics at University College London but found the subject's lack of human relevance uncongenial and switched to psychology, taking a PhD in 1940 under Cyril Burt. The choice of supervisor proved consequential in ways that are now uncomfortable: Burt's own data on the heritability of intelligence were later found to be fabricated, and Eysenck became one of his most loyal defenders long after the doubts had become public. From Burt he took two commitments that shaped everything that followed — that individual differences are largely inherited, and that factor analysis is the appropriate tool for establishing what those differences are.

Academic and Professional Career

During the Second World War Eysenck worked as a research psychologist at the Mill Hill Emergency Hospital, where he was responsible for assessing shell-shocked servicemen. The work convinced him that neurotic breakdown had a structured, measurable form and could be studied with the instruments of experimental psychology rather than interpretation. In 1945 he moved to the Maudsley Hospital in south London, and in 1955 he was appointed professor of psychology at the Institute of Psychiatry, then part of the University of London and now of King's College London. He held the chair until 1983.

Three projects defined the Maudsley years. The first was the construction of a dimensional model of personality out of factor analysis, beginning with Dimensions of Personality (1947) and consolidated in The Structure of Human Personality (1952). The second was the development of instruments: the Maudsley Medical Questionnaire (1952), the Maudsley Personality Inventory (1959), the Eysenck Personality Inventory (1964) and the Eysenck Personality Questionnaire (1975), the last adding psychoticism and becoming one of the most widely used personality scales in the world. The third was an attack on psychoanalysis. A 1952 review of the outcome literature concluded that there was no evidence patients treated by psychoanalytic methods improved more than untreated controls; the argument, expanded in The Effects of Psychotherapy (1966), helped make the evaluation of psychotherapy a legitimate research question and helped establish behaviour therapy as a clinical alternative.

Eysenck founded the journal Personality and Individual Differences in 1980, was a founding member of the World Cultural Council in 1981, and in 1994 was one of fifty-two signatories of "Mainstream Science on Intelligence", a statement defending the argument of The Bell Curve. He also devoted serious attention to parapsychology and to astrology, arguing that some experimental evidence supported anomalous cognition — a preoccupation his critics have cited as a symptom of methodological overconfidence.

Major Contributions to Psychology

The PEN Model of Personality

Eysenck's model is hierarchical. At the bottom sit specific responses and habits; these cluster into traits, traits into the three super-factors. Extraversion, on his account, reflects baseline cortical arousal: introverts run at a chronically higher level of excitation and so avoid stimulation, extraverts run lower and seek it. Neuroticism reflects the reactivity of the limbic system and the lability of the autonomic nervous system, so that high scorers respond more strongly and recover more slowly to threat. Psychoticism, added in the 1970s primarily to account for antisocial and schizotypal behaviour, was linked by Eysenck to androgen levels and to monoamine oxidase. The causal hypotheses have not all survived, but the framework — that personality dimensions should be explained by identifiable neural systems — is now standard practice in personality psychology.

Intelligence and the Biological Basis of Ability

Eysenck treated intelligence as a biological property of the nervous system, measurable through reaction time and inspection time as well as through test scores, and argued that the speed and efficiency of elementary cognitive operations explained much of the variance in general ability. This "biological" approach to g was influential and remains an active research programme, though the specific claim that reaction time causally explains g is contested.

Psychometrics and Behaviour Genetics

Eysenck was a relentless advocate for psychometric rigour in a field he considered slack: he insisted on testable models, on adequate samples, and on the use of twin and adoption designs to separate heredity from environment. His insistence that personality traits are substantially heritable — he put the figure at roughly half the variance — was unfashionable in the 1950s and is now broadly accepted.

The Critique of Psychoanalysis

Eysenck's objection to psychoanalysis was evidential rather than ideological. He argued that the theory made no testable predictions about outcome, that the case material was selected and unverifiable, and that spontaneous remission rates made uncontrolled claims of cure meaningless. The Experimental Study of Freudian Theories (1973), with G. D. Wilson, subjected the theory's mechanisms to laboratory test and found little support.

Major Publications

  • Dimensions of Personality (1947) — the first statement of the two-factor model
  • The Structure of Human Personality (1952) — the systematic synthesis, revised across three editions
  • "The Effects of Psychotherapy: An Evaluation" (1952) — the outcome review that launched the psychotherapy effectiveness debate
  • Uses and Abuses of Psychology (1953) — a polemic against what he saw as unfalsifiable psychology
  • Manual of the Maudsley Personality Inventory (1959) — the instrument that operationalised extraversion and neuroticism
  • The Causes and Cures of Neuroses (1965, with Stanley Rachman) — the behaviour-therapeutic alternative to psychoanalytic treatment
  • Smoking, Health and Personality (1965) — the beginning of the work that would later be discredited
  • The Biological Basis of Personality (1967) — the fullest attempt to ground the dimensions in physiology
  • Race, Intelligence and Education (1971, US title The IQ Argument) — his most contested book
  • The Inequality of Man (1973) — the hereditarian argument extended to social policy
  • Manual of the Eysenck Personality Questionnaire (1975, with Sybil B. G. Eysenck) — the PEN instrument

Impact and Legacy

Eysenck shaped psychology in ways that have outlasted his specific claims. Trait psychology's commitment to measurement, its biological ambition, and its expectation that personality constructs must be located in the nervous system are largely his legacy. Behaviour therapy owes much of its early confidence to his attacks on psychoanalysis. Generations of British clinical psychologists were trained in an Institute of Psychiatry that bore his stamp. In a 2002 ranking of the most eminent psychologists of the twentieth century, published in Review of General Psychology, he placed twenty-fourth.

The reassessment that began after his death is severe and, on the evidence, justified. The largest problem concerns his work with the Heidelberg physician Ronald Grossarth-Maticek on personality and disease. Across some twenty-five papers published between 1988 and 2000, the pair reported that "cancer-prone" and "coronary-prone" personality types carried risks of death forty, sixty, even seventy times higher than those with a "healthy" personality — magnitudes unheard of in epidemiology, where established associations are typically well under a factor of two. They also reported that brief behavioural intervention could cut cancer mortality by large margins. An inquiry conducted for King's College London could not obtain the underlying raw data, which were said to come from cohorts of thirty thousand people tracked for fifteen to twenty years in Yugoslavia and Heidelberg, and found no ethics-committee protocols. A ten-year replication effort by Manfred Amelang, following five thousand Heidelberg residents, found no association between Eysenck's personality types and disease. Twenty-six of the papers were declared "unsafe" in 2019; fourteen were retracted in 2020; journals issued sixty-four statements of concern. David Marks and Rod Buchanan have argued that eighty-seven of his publications should be retracted altogether.

A connected problem is the funding. Anthony Pelosi, who first documented the anomalies in the British Medical Journal in 1992, later unearthed records showing that the tobacco industry had funded several of Eysenck's studies and underwritten Grossarth-Maticek's cohort work — a convergence of interest worth stating plainly: Eysenck had publicly questioned, in 1965, whether cigarettes caused lung cancer, and a finding that personality rather than smoking caused the disease was commercially useful.

His work on race and intelligence has not fared better. In Race, Intelligence and Education and elsewhere he argued that average group differences in IQ were substantially genetic in origin, citing a figure of roughly twelve points between Black and white children in the United States. That claim rests on assumptions about the comparability of tests across environments that the evidence does not support; subsequent work on the Flynn effect, on adoption and on the closing of gaps has made the hereditarian interpretation of group differences untenable as stated, and it is not accepted within mainstream psychology. In 1970s Britain his writing was cited in defence of discriminatory schooling.

Two further criticisms belong in any balanced account. Methodologically, Eysenck's factor-analytic conclusions were often more confident than his data warranted, and his three-factor solution is now generally regarded as too coarse — the five-factor model displaced it largely because it captures distinctions his model collapses. And his defence of Burt, sustained long after the fabrication allegations, damaged his judgment as a custodian of the field's standards.

What survives is real: a model of personality that is still taught, instruments still in use, a conception of intelligence as a biological phenomenon, and a demonstration that therapeutic claims require evidence. What has been withdrawn is also real, and the field is still working out how much of the rest rests on it.

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References

  • Eysenck, H. J. (1947). Dimensions of Personality. Routledge & Kegan Paul.

Last updated: 2026-10-20

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