Feist−Feist: Theories of
Personality, Seventh
EditionIV. Dispositional Theories 14. Eysenck, McCrae, and
Costa’s Trait and Factor
Theories(^418) © The McGraw−Hill
Companies, 2009
differences between extraversion and introversion are not behavioral, but rather bio-
logical and genetic in nature.
Eysenck (1997a) believed that the primary cause of differences between ex-
traverts and introverts is one of cortical arousal level,a physiological condition that
is largely inherited rather than learned. Because extraverts have a lower level of cor-
tical arousal than do introverts, they have higher sensory thresholds and thus lesser
reactions to sensory stimulation. Introverts, conversely, are characterized by a higher
level of arousal, and as a result of a lower sensory threshold, they experience greater
reactions to sensory stimulation. To maintain an optimal level of stimulation, intro-
verts, with their congenitally low sensory threshold, avoid situations that will cause
too much excitement. Hence, introverts shun such activities as wild social events,
downhill skiing, skydiving, competitive sports, leading a fraternity or sorority, or
playing practical jokes.
Conversely, because extraverts have a habitually low level of cortical arousal,
they need a high level of sensory stimulation to maintain an optimal level of stimu-
lation. Therefore, extraverts participate more often in exciting and stimulating activ-
ities. They may enjoy such activities as mountain climbing, gambling, driving fast
cars, drinking alcohol, and smoking marijuana. In addition, Eysenck (1976) hypoth-
esized that extraverts, as opposed to introverts, will engage in sexual intercourse ear-
lier, more frequently, with a wider range of partners, in a greater number of posi-
tions, with a larger variety of sexual behaviors, and will indulge in longer precoital
love play. Because extraverts have a lower level of cortical arousal, however, they be-
come more quickly accustomed to strong stimuli (sexual or otherwise) and respond
less and less to the same stimuli, whereas introverts are less likely to become bored
and uninterested in routine activities carried on with the same people.
Neuroticism
The second superfactor extracted by Eysenck is neuroticism/stability (N). Like ex-
traversion/introversion, Factor N has a strong hereditary component. Eysenck (1967)
reported several studies that have found evidence of a genetic basis for such neurotic
traits as anxiety, hysteria, and obsessive-compulsive disorders. In addition, he found
a much greater agreement among identical twins than among fraternal twins on a
number of antisocial and asocial behaviors such as adult crime, childhood behavior
disorders, homosexuality, and alcoholism (Eysenck, 1964).
People who score high on neuroticism often have a tendency to overreact emo-
tionally and to have difficulty returning to a normal state after emotional arousal.
They frequently complain of physical symptoms such as headache and backache and
of vague psychological problems such as worries and anxieties. Neuroticism, how-
ever, does not necessarily suggest a neurosis in the traditional meaning of that term.
People can score high on neuroticism and be free of any debilitating psychological
symptoms.
Eysenck accepted the diathesis-stress model of psychiatric illness, which
suggests that some people are vulnerable to illness because they have either a genetic
or an acquired weakness that predisposes them to an illness. This predisposition
(diathesis) may interact with stress to produce a neurotic disorder. Eysenck assumed
that people at the healthy end of the N scale have the capacity to resist a neurotic dis-
412 Part IV Dispositional Theories