Chapter 14 Eysenck’s Biologically Based Factor Theory 421to the other two.) Eysenck’s view of personality, therefore, allows each person to
be measured on three independent factors and resultant scores to be plotted in space
having three coordinates. Person F in Figure 14.4, for example, is quite high on
superego, somewhat high on extraversion, and near the midpoint on the neuroticism/
stability scale. In similar fashion, scores of each person can be plotted in three-
dimensional space.
Measuring Personality
Eysenck evolved four personality inventories that measure his superfactors. The
first, the Maudsley Personality Inventory, or MPI (Eysenck, 1959), assessed only
E and N and yielded some correlation between these two factors. For this reason,
Eysenck developed another test, the Eysenck Personality Inventory, or EPI. The EPI
contains a lie (L) scale to detect faking, but more importantly, it measures extraver-
sion and neuroticism independently, with a near zero correlation between E and N
(H. J. Eysenck & B. G. Eysenck, 1964, 1968). The Eysenck Personality Inventory
was extended to children 7 to 16 years of age by Sybil B. G. Eysenck (1965), who
developed the Junior EPI.
The EPI was still a two-factor inventory, so consequently Hans Eysenck and
Sybil Eysenck (1975) published a third personality test, namely the Eysenck Per-
sonality Questionnaire (EPQ), which included a psychoticism (P) scale. The EPQ,
which has both an adult and a junior version, is a revision of the still-published
EPI. Subsequent criticisms of the P scale led to yet another revision, the Eysenck
Personality Questionnaire-Revised (H. J. Eysenck & S. B. G. Eysenck, 1993).
Biological Bases of Personality
According to Eysenck, personality factors P, E, and N all have powerful biological
determinants. He estimated that about three fourths of the variance of all three
personality dimensions can be accounted for by heredity and about one fourth by
environmental factors.
Eysenck (1990) cited three threads of evidence for a strong biological com-
ponent in personality. First, researchers (McCrae & Allik, 2002) have found nearly
identical factors among people in various parts of the world, not only in Western
Europe and North America but also in Uganda, Nigeria, Japan, China, Russia, and
other African and European countries. Second, evidence (McCrae & Costa, 2003)
suggests that individuals tend to maintain their position over time on the different
dimensions of personality. And third, studies of twins (Eysenck, 1990) show a
higher concordance between identical twins than between same-gender fraternal
twins reared together, suggesting that genetic factors play a dominant part in deter-
mining individual differences in personality.
In Eysenck’s theory of personality, psychoticism, extraversion, and neuroticism
have both antecedents and consequences. The antecedents are genetic and biological,
whereas the consequences include such experimental variables as conditioning expe-
riences, sensitivity, and memory as well as social behaviors such as criminality,
creativity, psychopathology, and sexual behavior. Figure 14.5 shows that P, E, and N