Eysenck’s Biologically Based Factor Theory

  1. Overview of Factor and Trait Theories

Hans Eysenck and others have used factor analysis to identify traits, that is, relatively permanent dispositions of people.  Eysenck extracted only three general factors,which yielded three general bipolar factors or types: extraversion/introversion, neuroticism/stability, and psychoticism/superego.


  1. Biography of Hans J. Eysenck

Hans J. Eysenck was born in Berlin in 1916, but as a teenager, he moved to London to escape Nazi tyranny.  Eysenck was trained in the psychometrically oriented psychology department of the University of London, from which he received a bachelor’s degree in 1938 and a PhD in 1940.  Eysenck was perhaps the most prolific writer of any psychologist in the world, and his books and articles often stirred worldwide controversy.  He died in September of 1997.



III.   Eysenck’s Factor Theory

         The personality theory of Hans Eysenck has strong psychometric and biological components. Hans Eysenck (1) was more likely to theorize before collecting and analyzing data; (2) extracted fewer factors; (3) used a wider variety of approaches to gather data.

  1. Criteria for Identifying Factors

Eysenck insisted that personality factors must (1) be based on strong psychometric evidence, (2) fit an acceptable genetic model, (3) make sense theoretically, and (4) possess social relevance.

  1. Hierarchy of Behavior Organization

Eysenck recognized a four-level hierarchy of behavior organization: (1) specific behaviors or cognitions; (2) habitual acts or cognitions; (3) traits, or personal dispositions, and (4) types or superfactors.


  1. Dimensions of Personality

Although many triads exist, Eysenck’s methods of measuring personality limited the number bipolar personality types to only three—extraversion/introversion, neuroticism/stability, and psychoticism/superego function.  Each of three bipolar factors has a strong genetic component.

  1. Extraversion

Extraverts are characterized by sociability, impulsiveness, jocularity, liveliness, optimism, and quick-wittedness, whereas introverts are quiet, passive, unsociable, careful, reserved, thoughtful, pessimistic, peaceful, sober, and controlled.  Eysenck, however, believed that the principal difference between extraverts and introverts is one of cortical arousal level.

  1. Neuroticism

Like extraversion/introversion, neuroticism/stability is largely influenced by genetic factors.  People high in neuroticism have such traits as anxiety, hysteria, and obsessive-compulsive disorders.  They frequently have a tendency to overreact emotionally and to have difficulty returning to a normal state after emotional arousal.  They often complain of physical symptoms such as headache and backache, but they also may be free from psychological symptoms.

  1. Psychoticism

The latest and weakest of Eysenck’s personality factors is psychoticism/superego.  High psychotic scores may indicate anxiety, hysteria, egocentricism, nonconformance, aggression, impulsiveness, hostility, and obsessive-compulsive disorders.  Both normal and abnormal individuals may score high on the neuroticism scale.

  1. Measuring Personality

Eysenck and his colleagues developed four personality inventory to measure superfactors, or types  The two most frequently used by current researchers is the Eysenck Personality Inventory (which measures only E and N) and the Eysenck Personality Questionnaire (which also measures all three factors).

  1. Biological Bases of Personality

Eysenck believed that P, E, and N all have a powerful biological components, and he cited as evidence the existence of these three types in a wide variety of cultures and languages.

VII.  Personality as a Predictor

Eysenck’s complex model of personality suggests that the psychometric traits of P, E, and N can combine with one another and with genetic determinants, biological intermediates, and experimental studies to predict a variety of social behaviors, including those that contribute to disease.

  1. Personality and Behavior

According to Eysenck’s model, P, E, and N should predict both proximal and distal consequences (see Figure 14.7), and he and his colleagues cited studies that predicted behavior in both laboratory studies and studies of social behavior.  They found a relationship between superfactors and a large number of behaviors and processes, such as academic performance, creativity, antisocial behavior, as well as behaviors that may lead to disease.

  1. Personality and Disease

For many years, Eysenck researched the relationship between personality factors and disease.  He teamed with Ronald Grossarth-Maticek to study the connection between personality characteristics and both cancer and cardiovascular disease.  According to this research, people with a helpless/hopeless attitude are more likely to die from cancer, whereas people who react to frustration with anger and emotional arousal are more much more likely to die from cardiovascular disease.




VIII.      Related Research

The three-factor theory of Eysenck has drawn a considerable amount of research, and is very popular in the field of personality.  Eysenck developed the Eysenck Personality Inventory and its offshoots (Eysenck, 1959; Eysenck & Eysenck, 1964, 1968, 1975, 1993)

         Biology and Personality

Eysenck assumed that personality springs from genetic and neurophysiological bases.  If this assumption has validity,  neurophysiological differences should exist between people high on one end of a dimension (for instance, introversion) and those high on the other end of that dimension (extraverts).  Second, the basic personality dimensions should be universal and not limited to a given culture.  Over the last 30 years, a substantial amount of research has shown physiological differences between extraverts and introverts, thus supporting Eysenck’s biology-based theory (Beauducel, Brocke, & Leue, 2006; Eysenck, 1990; Stelmack, 1990, 1997). Interestingly, one study found that extraverts may move faster, but they do not think faster than introverts (Doucet & Stelmack, 2000).  Another of Eysenck’s hypotheses that has generated some research is optimal level of arousal.  Eysenck theorized that introverts should work best with lower levels of sensory stimulation and extraverts with higher levels (Dornic & Ekehammer, 1990).  Russell Geen studied this (1984), and his findings supported Eysenck’s theory.



  1. Critique of Factor Theories

The factor theories of Eysenck and others rate high on parsimony, on their ability to generate research, and on their usefulness in organizing data; they are about average on falsifiability, usefulness to the practitioner, and internal consistency.

  1. Concept of Humanity

Factor theories generally assume that human personality is largely the product of genetics and not the environment.  Thus, we rate these two theories very high on biological influences and very low on social factors.  In addition, we rate both about average on conscious versus unconscious influences and high on the uniqueness of individuals.  The concepts of free choice, optimism versus pessimism, and causality versus teleology are not clearly addressed by these theories.


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