98 Biological Bases of Personality
Eysenck’s psychoticism scale is one of the best markers for
the dimension that consists of scales for impulsivity and
sensation seeking at one pole and scales for socialization,
responsibility, and restraint at the other pole (Zuckerman
et al., 1988, 1991, 1993). In a three-factor solution this
factor also includes aggression and capacity to inhibit
aggression, but in a four- or five-factor solution aggression
and hostility versus agreeableness form a separate factor
(Zuckerman et al., 1993). This chapter is organized by the
four-factor model.
Cortical Arousal and Arousability
At the time the original studies were done relating condition-
ing to arousal and the construct “strength of the nervous sys-
tem” to extraversion, E was measured by scales with two
components: E and Impulsivity (Imp). In a theoretical shift,
not receiving much attention, Eysenck and Eysenck (1985) re-
assigned Imp to the P rather than the E dimension. Although
nearly all the earlier arousal and conditioning studies focused
on E, it was shown that the relationship of E to conditionabil-
ity (introverts more conditionable than extraverts) depended
on the Imp component of E rather than the sociability compo-
nent (Barratt, 1971; Eysenck & Levey, 1972). A later study
showed that classical eyelid conditoning was related most
closely to a specific type of Imp, the tendency to act quickly on
impulse without thinking or planning. This is the type of Imp,
callednarrow impulsivity(IMPn), that constitutes a subscale
of the older E scale. It is also the type of Imp that has been
combined with sensation seeking in the latest ImpSS scale.
Conditionability is thought to be a function of arousal; the
more aroused a person is, the more conditionable he or she is
thought to be. Could this mean that cortical arousal is related
to the third dimension (P), including sensation seeking and
IMPn, rather than the first (E) dimension of personality? A
PET study found negative correlations between P and glucose
use in cortex and in thalamic and cingulate areas of the limbic
system (Haier et al., 1987). Low cortical and autonomic
arousal is a characteristic of the psychopathic (antisocial) per-
sonality, which may represent an extreme manifestation of the
P dimension of personality (Zuckerman, 1989).
Evidence for a relationship between cortical arousal
(EEG) and P and IMPn was found by some investigators
(Goldring & Richards, 1985; O’Gorman & Lloyd, 1987);
high P and impulsive subjects were underaroused. Sensation
seeking, however, was not related to tonic arousal. Instead,
sensation seeking—particularly that of the disinhibitiory
type—has been consistently related to a particular measure of
cortical arousability called augmenting-reducing (A-R,
Buchsbaum, 1971).
A-R asseses the relationship of cortical reactivity, mea-
sured as a function of the relationship between the cortical EP
and stimulus intensity for any given individual. A strong pos-
itive relationship between the amplitude of the EP and the in-
tensity of stimuli is called augmenting, and a negative or zero
relationship is called reducing. A-R differences are most
often observed at the highest intensities of stimulation, where
the reducers show a marked EP reduction and the augmenters
continue to show increased EP amplitude. There is an obvi-
ous relevance of this measure to Pavlov’s (1927/1960) con-
struct of “strength of the nervous system,” based on the
nervous system’s capacity to respond to high intensities of
stimulation without showing transmarginal inhibition.
Figure 4.3 shows the first study of the relationship be-
tween the Disinhibition (Dis) subscale of the SSS and ampli-
tude of the visual EP. Those scoring high on Dis displayed an
augmenting pattern, and those scoring low on this scale
showed a strong reducing pattern, particularly at the highest
intensity of stimulation. This study was followed by many
others, some using visual and others using auditory stimuli.
Replications were frequent, particularly for the auditory EP
(Zuckerman, 1990, 1991). Replications continue to appear
(Brocke, Beauducel, John, Debener, & Heilemann, 2000;
Stenberg, Rosen, & Risberg, 1990). A-R has also been found
to be related to Imp, particularly cognitive impulsiveness
(Barratt, Pritchard, Faulk, & Brandt, 1987).
The A-R model has been extended to other species and
used as a biological marker for behavioral traits in animals
resembling those in high and low human sensation seekers
and impulsive and constrained persons. Cats who showed theFigure 4.3Mean visual evoked potential amplitudes (P1-N1) at five levels
of light intensity for low and high scorers on the disinhibition subscale of the
Sensation Seeking Scale.
From “Sensation seeking and cortical augmenting-reducing,” by M.
Zuckerman, T. T. Murtaugh, and J. Siegel, 1974, Psychophysiology, 11,
p. 539. Copyright 1974 by the Society for Psychophysiological Research.
Reprinted by permission.