have evidence for the second level in Eysenck ’s model, a habitual response.
But it is unlikely that this man limits himself to socializing just in the after-
noon and just with these friends. Suppose this man also devotes a large partof his weekends and quite a few evenings to his social life. If you watch long
enough, you might find that he lives for social gatherings, group discussions,
parties, and so on. You might conclude, in Eysenck ’s terms, that this person
exhibits the trait of sociability. Eysenck also argued that traits such as socia-
bility are part of a still larger dimension of personality. That is, people whoare sociable also tend to be impulsive, active, lively, and excitable. All of thesetraits combine to form the supertrait Eysenck calls extraversion.
How many of these supertraits are there? Originally, Eysenck ’s factor an-
alytic research yielded evidence for two basic dimensions that could subsumeall other traits: extraversion –introversion and neuroticism . Because the dimen-
sions are independent of one another, people who score on the extraversion
end of the first dimension can score either high or low on the second dimen-
sion. Further, as shown in Figure 9.2, someone who scores high on extraver-
sion and low on neuroticism possesses traits different from a person who
scores high on both extraversion and neuroticism.
If you are the prototypic extravert, you are “outgoing, impulsive, and un-
inhibited, having many social contacts and frequently taking part in group ac-tivities. The typical extravert is sociable, likes parties, has many friends, needs
to have people to talk to, and does not like reading or studying by himself ”
(Eysenck & Eysenck, 1968, p. 6). An introvert is “a quiet, retiring sort ofSupertrait
Level:Extraversion
Trait
Level:Sociability Impulsiveness Activity Liveliness Excitability
HabitualResponseLevel:
Specific
ResponseLevel:
HR1
HR2
HR3
HR4SR1
SR2
SR3
SR4
SRn–1SRnHRn–1
HRn
FIGURE 9.1 Eysenck ’s Hierarchical Model of Personality224 CHAPTER 9 The Biological Approach