Feist−Feist: Theories of
Personality, Seventh
EditionIV. Dispositional Theories 14. Eysenck, McCrae, and
Costa’s Trait and Factor
Theories(^436) © The McGraw−Hill
Companies, 2009
do extraverts, then they should be more reactive (that is, sensitive) to sensory stim-
ulation. One way to test this idea is to present both groups with varying intensities
of stimulation and measure their physiological reactivity. If Eysenck’s theory is to be
supported, then introverts should be more reactive than extraverts.
Over the past 30 years, a substantial amount of research has explored cogni-
tive, behavioral, and physiological measures of reactivity in relation to extraversion-
introversion (Beauducel, Brocke, & Leue, 2006; Eysenck, 1990; Stelmack, 1990,
1997). In general, Eysenck’s assumption that introverts are more reactive (have lower
thresholds) than extraverts has been supported, with the qualification that it is reac-
tivity rather than baseline activity levels that distinguishes introverts from extraverts.
For instance, in a recent study, Beauducel and colleagues (2006) predicted that
extraverts would be less cortically aroused and show worse performance on a boring
and monotonous task. The researchers selected students who scored either very low
or very high on the Eysenck Personality Questionnaire–Extraversion scale. They
then presented the participants with a series of tones every 3 seconds for 60 minutes.
Participants had to press a button as soon as possible after they heard a target tone.
Computers measured both the speed (reaction time) and accuracy of responses. The
task was meant to be tedious and boring, and it was. The idea is that extraverts will
do worse at the tone task because it is so understimulating. Finally, the participants’
cortical activity was measured via EEG throughout the entire tone task. The predic-
tions again were that extraverts would have lower cortical arousal and would do
worse on the monotonous task. Beauducel and colleagues found support for both of
these hypotheses, which support two of the most basic of Eysenck’s assumptions
about the biological basis of personality traits.
Similarly, Anthony Gale (1983) summarized the findings from 33 studies ex-
amining EEG and extraversion and found that introverts showed greater cortical
arousal than did extraverts in 22 of the 33 studies. Later, Robert Stelmack (1997), a
major figure in testing Eysenck’s neurophysiological hypothesis, reviewed the liter-
ature and came to two basic conclusions: First, introverts are more reactive than ex-
traverts on various measures of arousal; and second, extraverts are quicker to re-
spond on simple motor tasks. The faster motoric response rates of extraverts
correspond well with their greater spontaneity, social disinhibition, and impulsive-
ness. In a study by Cynthia Doucet and Stelmack (2000), however, it was only mo-
toric response rate—not cognitive processing speed—that differentiated introverts
and extraverts. Extraverts were faster motorically but not cognitively. Extraverts may
move faster but they do not think faster than introverts.
Optimal level of arousal is another of Eysenck’s hypotheses that has gener-
ated some research. Eysenck theorized that introverts should work best in environ-
ments of relatively low sensory stimulation, whereas extraverts should perform best
under conditions of relatively high sensory stimulation (Dornic & Ekehammer,
1990). In an important study conducted by Russell Geen (1984), introverted and ex-
traverted participants were randomly assigned to either a low noise or high noise
condition and then given a relatively simple cognitive task to perform. Results
showed that introverts outperformed extraverts under conditions of low noise,
whereas extraverts outperformed introverts under conditions of high noise. These
findings not only support Eysenck’s theory but also suggest that people who prefer
to study in public places (like a dorm study area) are more likely to be extraverts.
430 Part IV Dispositional Theories