9781412946513-Ch01 12/14/07 3:52 PM Page 31 PART I Explanatory Models For Personality 9781412946513-Ch01 12/14/07 3:52 PM Page 32 9781412946513-Ch01 12/14/07 3:52 PM Page 33 1 Psychophysiological and Biochemical Correlates of Personality Robert M. Stelmack and Thomas H. Rammsayer The degree of activation, as shown by the writer in personality literature, Duffy (1962: 273) various publications (Duffy, 1962), appears to affect both sensory sensitivity and motor response, and is concluded that ‘Any survey of physiological involved in those consistencies of behavior that we studies of personality must recognize the sur- call personality characteristics. (Duffy, 1966: 281) prising fact that relatively few investigators have reported relationships of any magnitude between physiological measures and measures of behavior within the normal INTRODUCTION population.’ Since that time, however, there was considerable progress in delineating reli- Considering that these quoted words were able relations between personality traits and written by Elizabeth Duffy 40 years ago, the physiological processes. This progress was view expressed was prescient indeed. There abetted by the development of rigorous per- is considerable evidence today, from psy- sonality typologies; by compelling, large- chophysical, psychophysiological and bio- scale projects determining the heritability of chemical procedures (formerly considered personality traits; by refinement and develop- measures of activation), establishing that the ment of physiological measurement proce- personality dimension of extraversion (E) is dures; and by exploiting new paradigms for characterized by individual differences in probing psychological processes such as sensitivity to simple physical stimulation and sensation, attention, learning and memory in the expression of motor responses. At the that are manifest in individual differences in time when Duffy expressed her views, how- personality. In this chapter, we mark this ever, the association of personality with sen- progress by assessing the current status of sory sensitivity and motor processes was far the psychophysiological and biochemical from clear. In fact, in an assessment of the correlates of personality traits. 9781412946513-Ch01 12/14/07 3:52 PM Page 34 34 THE SAGE HANDBOOK OF PERSONALITY THEORY AND ASSESSMENT The nomenclatural framework for the thresholds (e.g. Dornic and Ekehammer, present review consists of the three major 1990), larger skin conductance responses to personality dimensions of E, emotional moderate intensity tones (e.g. Smith, 1983), stability–instability/neuroticism (N), and and larger ERP amplitude to simple physical psychoticism (P)/impulsive sensation-seeking stimulation (e.g. Stelmack and Michaud- (ImpSS). These personality traits emerge as Achorn, 1985). Moreover, there was evidence fundamental factors in most major personality from brainstem auditory evoked potentials typologies (e.g. Costa and McCrae, 1992; indicating that these intensity effects are Eysenck and Eysenck, 1991; Zuckerman, evident at the level of the auditory nerve (e.g. 2002) and they capture the bulk of psy- Stelmack and Wilson, 1982). These effects chophysiological and biochemical research meld with the preference of introverts for on individual differences in personality. quiet and solitude (Campbell and Hawley, An emphasis in this review is placed on 1982) and with their tendency toward with- electrocortical procedures (i.e. electroen- drawal as a coping strategy in stressful social cephalography (EEG) and event-related situations (Endler and Parker, 1990). potentials (ERPs)), and biochemical analyses Introverts and extraverts differ in their (i.e. dopamine, serotonin, and cortisol), expression of motor behaviour on a variety of because these measurement procedures tasks that require a simple motor response, predominate in current research on personality. with extraverts initiating faster and more fre- Conclusions drawn from earlier reviews of quent responses than introverts (e.g. Brebner research on the biological bases of personal- and Flavell, 1978). These effects appear ity are briefly stated. An attempt is made relevant to the disposition of extraverts to to focus the functional significance of liveliness, activity, and talkativeness the biological procedures and paradigms on (Eysenck and Eysenck, 1975), involvement the social and behavioural expressions that in athletic activities (Eysenck et al., 1982), characterize the personality dimensions, but restlessness in restricted environments (Gale, the theoretical frameworks that inspired 1969), and preference for physical activity much of this research are left to other authors (Furnham, 1981). Moreover, there was in this volume. evidence employing psychophysiological procedures that differences in motor activity between introverts and extraverts can be referred to peripheral nervous system PSYCHOPHYSIOLOGICAL AND processes (Stelmack and Pivik, 1996). There BIOCHEMICAL CORRELATES OF is good evidence that variation in dopaminer- EXTRAVERSION gic activity (DA) is an important determinant of differences in E (e.g. Rammsayer et al., In previous reviews, it was concluded that 1993). In general, more recent research on there were fundamental differences between E and differences in sensory sensitivity and introverts and extraverts in their reaction to motor expression, using electrocortical and sensory stimulation and in their expression of biochemical measurement procedures, motor activity (Matthews and Gilliland, endorse these findings. 1999; Stelmack, 1997). There is compelling evidence from a range of measurement pro- cedures indicating that introverts are more Extraversion and the reactive or sensitive to simple sensory stimu- electroencephalograph lation than are extraverts. Introverts display lower absolute auditory sensitivity (e.g. The electroencephalograph (EEG), recording Stelmack and Campbell, 1974), lower pain electrical activity of the brain from small elec- thresholds (e.g. Barnes, 1975), lower noise trodes affixed to the scalp, was an important 9781412946513-Ch01 12/14/07 3:52 PM Page 35 PSYCHOPHYSIOLOGICAL AND BIOCHEMICAL CORRELATES OF PERSONALITY 35 method for assessing cortical activity of the EEG can be made. An exception here is the brain in the early study of the ascending work by Knyazev et al. (2002), where partic- reticular activating system (ARAS; Lindsley, ipants performed mental arithmetic during 1951) and in exploring the role of the ARAS the EEG recording in an attempt to manipu- in attention, memory and learning. The late arousal level. Even in this case, however, hypothesis that differences in E were deter- the behavioural effect of this manipulation mined by differences in cortical excitation was not measured. and inhibition (Eysenck, 1957) and cortical There was considerable interest in the arousal (Eysenck, 1967) fostered extensive claim that activation of right anterior cortical analysis of E and the EEG. In early reviews areas is associated with the expression of (Gale, 1973; O’Gorman, 1977), support for negative affect, whereas activation of left the notion that introverts are characterized by anterior cortical areas is associated with the higher levels of cortical arousal (indexed by expression of positive affect (Davidson and lower EEG alpha wave activity) than Fox, 1982). Investigation of these effects was extraverts was equivocal. These reviews did drawn into the personality domain by prompt improvements in design and recording Hagemann et al. (1999) who exploited the techniques in subsequent research. Later association of E with positive affect and reviews conceded that the direction of the N with negative affect (Tellegen, 1985). results of these inquiries is towards higher Contrary to expectations, higher negative levels of cortical activity for introverts affect scores were associated with greater (Matthews and Gilliland, 1999; Stelmack activation at left anterior temporal cortical and Geen, 1992). areas. As Hagemann et al. (1999) note, this In more recent research, the ambiguous result is typical of the mixed outcomes that history of research on E using EEG recording plague EEG research on emotion and mood. is continued rather than clarified. The specific No differences in EEG activity between conditions under which reliable effects are introverts and extraverts were observed. replicated remain indeterminate. Tran et al. The line of inquiry initiated by Hagemann (2001) observed greater EEG activity in the et al. (1999) was pursued by Gale et al. 8–13 Hz (alpha) frequency range for (2001). During EEG recording, participants extraverts than introverts but only at frontal were asked to empathise and rate photo- electrode sites. This contrasts with other graphs expressing positive and negative positive reports (e.g. O’Gorman and Lloyd, affect. Negative valence photographs elicited 1987) showing greater EEG activity at poste- greater activation at left frontal cortical sites, rior electrode sites where alpha activity is an effect that endorses the sensitivity of the maximal. In a project similar to Tran et al. EEG measures to the affect manipulation. (2001), higher E was associated with greater Robust effects were reported with extraverts activity in low-frequency EEG bands (delta exhibiting greater alpha activity at frontal, and theta) at temporal and parietal sites, and temporal and occipital sites. lower alpha activity at temporal and frontal Gale et al. (2001) state that their data sites (Knyazev et al., 2002). In another well-