The extravert’s brain is the opposite of what we would expect; it is less excitable than the introvert’s.“Personality is determined to a large extent by a person’s genes; he is what the accidental arrangement of his parents’ genes produced, and while environment can do something to redress the balance, its influence is severely limited. Personality is in the same boat as intelligence; for both, the genetic influence is overwhelmingly strong, and the role of environment in most cases is reduced to effecting slight changes and perhaps a kind of cover-up.”
In a nutshell
All personalities can be measured according to two or three basic biologically determined dimensions.
In a similar vein
Isabel Briggs Myers Gifts Differing (p 46)
Ivan Pavlov Conditioned Reflexes (p 210)
Steven Pinker The Blank Slate (p 228)
Eysenck was one of the twentieth century’s most controversial and prolific psychologists. In a career spanning five decades, 50 books, and more than 900 journal articles, he shed new light on a number of areas. Born in Germany, his opposition to the Nazi party during the 1930s led to his fleeing to Britain. At the time of his death in 1997, he was the most-cited researcher in psychology.
Dimensions of Personality was Eysenck’s first book, and has a dry, academic style. However, in grounding for the first time in science the concept of introversion/extraversion, it laid the foundation for 50 years’ work in the field of personality difference.
Though Eysenck acknowledged the ancient Greek division of people into the four temperaments of sanguine, choleric, phlegmatic, and melancholy, and was obviously in debt to Carl Jung’s distinction between introverts and extraverts, he was also adamant that any study of personality differences had to be objective and statistically based. Dimensions of Personality was grounded in a method of research, factor analysis, which enabled Eysenck to draw conclusions about personality differences from large amounts of survey data. He had worked at the Mill Hill Emergency Hospital in wartime London, and used several hundred war-weary soldiers as his sample. The men were asked a battery of questions about their habitual reactions to certain situations and they gave themselves ratings. The collated answers led Eysenck to confidently place a person according to two broad dimensions or “supertraits” of extraversion/introversion and neuroticism.
Eysenck believed that these supertraits were genetically determined and were manifested in our physiology, specifically the brain and nervous system. In this he was inspired by Ivan Pavlov. The source of extraversion or introversion was in the varying levels of excitability of the brain; the driver of the neurotic dimension was an aspect of the nervous system that handled emotional responses to events.
Later, Eysenck added another dimension, psychoticism. Though it could indicate mental instability, more commonly a person’s placement within this dimension was an indicator of how much they were likely to be rebellious against the system or wild and reckless. Unlike the extraversion/introversion dimension, which measures sociability, psychoticism measures the extent to which someone is a socialized being living according to conventions, or in the extreme an antisocial psychotic or sociopath.
Together, the three dimensions of psychoticism–extraversion–neuroticism became known as the PEN model. Characteristics included:
The extravert’s brain is the opposite of what we would expect; it is less excitable than the introvert’s.
Because there is less going on inside, extraverts naturally seek outside stimulation and contact with others to really feel alive.
Extraverts have a more even-handed approach to events, with less anguish about how they are personally perceived.
Extraverts are also generally lively and optimistic, but can be restless risk takers and unreliable.
The introvert’s brain is more excitable, making them more vulnerable to moods and having intense inner lives.
As a result of this inner sensory overload, as a form of self-protection they naturally avoid too much social interaction, which they find mentally taxing. Or, because they have such a rich inner life, they simply do not need a lot of social interaction.
Because they seem to experience things more intensely, introverts have a deeper and more anguished response to life.
They are generally more reserved and serious, pessimistic, and can have issues with self-esteem and guilt.
Neuroticism is an indicator of how upset, nervous, worried, anxious, or stressed we have a tendency to be.
Scoring high on this dimension does not mean that people are neurotic, only that they have the sort of brain that predisposes them to neuroses. A low score indicates that they are more emotionally stable.
The neurotically minded over-respond to stimuli, while those who are not are calmer and can put things into perspective.
Neurotically minded introverts, in an effort to control the stimulation that comes into their minds, are susceptible to phobias and panic attacks. Neurotically minded extraverts tend to undervalue the impact of life events, and may develop neuroses of denial or repression.
Though Eysenck’s work on the biological basis of personality has been frequently criticized, it has also been increasingly validated by research. As Steven Pinker notes in The Blank Slate, studies of identical twins raised apart have demonstrated that only a small portion of personality is due to socialization. The rest is shaped by genetics.
There are now many other models of personality type—including the commonly used five-factor model of extraversion, agreeableness, conscientiousness, neuroticism, and openness—but Eysenck was the first to make the effort toward a statistical way of understanding the issue. It is unlikely that personality will ever be an exact science, but his work laid a foundation for better understanding of people that did not rely on mere social observation or folk wisdom.
As both a serious scientist and a writer of popular psychology books, Eysenck contributed greatly to increased public understanding of psychological issues. In the 1950s he made a celebrated attack on the scientific validity of psychoanalysis, stating that there was no evidence at all that it helped cure patients’ neuroses—and in the process he helped make psychotherapy more scientifically accountable and focused.
Eysenck was also known as an intelligence researcher who, going against the ethos of social conditioning, maintained that intelligence levels were largely heritable and genetic. His 1971 book Race, Intelligence and Education, which laid out evidence of IQ differences according to racial type, led to demonstrations and Eysenck’s famously being punched in the face at a university lecture. He also delved into astrology, gave some support to paranormal phenomena, suggested that smoking-related cancer was linked to personality, and presented evidence that some people had a biological disposition to be criminals.
Despite such controversies, toward the end of his life the American Psychological Society made Eysenck a William James Fellow for a lifetime of distinguished contribution to psychological science.
Born in Germany in 1916, after his parents’ divorce Hans Jürgen Eysenck was brought up by his grandmother.
As a young man he opposed the Nazi regime and left Germany for good. He settled in England, completing his PhD in psychology at the University of London in 1940. During the Second World War he worked at Mill Hill emergency hospital as a psychiatrist, and from 1945–50 was a psychologist at the Maudsley Hospital. He also established and became director of the psychology department at the University of London’s Institute of Psychiatry, a post he held until 1983.
Eysenck died in 1997.