Extraversion and sleep: A psychophysiological study of the arousal hypothesis

In order to examine Eysenck's (1967) hypothesis concerning the relationship between extraversion and arousal, autonomic measures were taken from introverts and extraverts immediately before sleep and during 6 hr of sleep. Introverts and extraverts did not differ in heart rate (HR) or skin-potential response rate (SPR) during the pre-sleep period. A variety of sleep-related measures of arousal provided no strong support for the hypothesis that introverts are more aroused than extraverts. The only consistent autonomic difference between introverts and extraverts during sleep was a tendency for introverts to have higher SPRs in the second 3 hr of the night. The results are discussed in terms of the level of environmental stimulation present in the experimental conditions, and suggestions are made for future sleep studies of the relationship between extraversion and arousal.     

Extraversion and the orienting reaction habituation rate to visual stimuli

Eysenck's (1967) proposal that introversion is characterized by increased levels of activity in the cortico-reticular loop was treated in a series of experiments which compared high, middle, and low extraversion groups on the basis of OR habituation rate to visual stimulation. Generally, introverts were observed to have longer OR habituation rates to chromatic and word stimulation than extraverts as evidenced by cardiac, electrodermal, and vasomotor indices of habituation rate, a result which endorses Eysenck's hypothesis. Results are also discussed from the standpoint of individual differences in autonomic response.     

Factor analytic examination of Kline's scales for psychoanalytic concepts

Seventeen personality scales were administered to 133 subjects to investigate the relation of three new psychoanalytically-derived scales to the personality scales of Howarth and Eysenck, respectively. A previous study (Howarth, 1980a) suggested that Kline's oral optimism scale related to Eysenck's extraversion scale, oral pessimism to neuroticism, and Kline's anal syndrome scale to Eysenck's psychoticism scale. In order to investigate this further Eysenck's scales were included as well as ten scales of Howarth's and Kline's three scales. The factors found among the 17 variables were: I. Anxiety; II. Psychoticism; III. Sociability; IV. Anality; V. Lie scale; VI. Conscience.The present study found that the anal scale was relatively independent of all of Eysenck's ‘superfactor’ scales and did not verify the possibility that this anal scale might relate to psychoticism (as measured by Eysenck). However, the present study verified the previously found relation between oral optimism and extraversion and, of the three Kline scales, oral pessimism related more to psychoticism than the anal syndrome scale.     

Extraversion,neuroticism, psychoticism and self-reported delinquency: Evidence from eight separate samples

Eight separate samples of high school and university students (Total N = 410) in Britain and Canada were used to test predictions from Eysenck's theory that delinquents should be high scorers on scales of extraversion, neuroticism, and psychoticism. Self-report paper- and pencil-questionnaire measures of both personality and delinquency were administered under conditions that ensured anonymity. The evidence showed clear support for a relationship between high delinquency scores and high scores on both extraversion and psychoticism. These relationships held up across diverse samples and different ways of analyzing the data. No support was found for a relationship between delinquency scores and the dimension of neuroticism.     

Do tough-minded people hold tough-minded attitudes?

Eysenck originally postulated that extraverts would adopt tough-minded social attitudes, although psychoticism is now considered to be of greater importance than extraversion. Previous research has attempted to relate psychoticism to realism-idealism, a principal factor of the Wilson-Patterson Conservatism Scale, and a measure of tough-mindedness acceptable to Eysenck. Results have proved discrepant; authors have used psychoticism scales of uncertain item content and length. The present study examines the relationship between psychoticism, extraversion and realism-idealism, using the Eysenck Personality Questionnaire and the Wilson-Patterson Attitude Inventory. The results provide only weak support for Eysenck’s theory. A more significant relationship was obtained between psychoticism and conservatism, and extraversion and conservatism, although a theoretical rationale for these relationships is lacking.     

Electrodermal responses to movie stressors: Nicotine × extraversion interactions

Support was found for Eysenck's hypothesis that the effects of smoking sized doses of nicotine on cortical and electrodermal activity are functions of extraversion and the degree of externally-induced arousal. Responses to scenes that elicited moderate electrodermal and emotional responses followed the predicted extraversion ☆ nicotine interaction for electrodermal measures, but not for self-reported emotions, heart rate or electromyographic measures. The failure of the Ss to demonstrate an extraversion ☆ nicotine interaction when high-intensity stimuli were used (Gilbert and Hagen, 1980) is also interpreted as consistent with Eysenck's hypothesis.     

Extraversion and attitude towards capital punishment

Male and female Canadian undergraduate students identified as extraverts or introverts on the basis of the Eysenck Personality Inventory were administered a questionnaire measuring attitude towards Capital Punishment. Both effects of sex and personality were significant, males and extraverts reporting stronger beliefs in Capital Punishment than females and introverts. These results were interpreted as providing support for Eysenck's proposal that the social attitude dimension of Toughmindedness reflects the personality trait of Extraversion.     

A six orthogonal factor model of adolescent personality derived from the HSPQ

Attention is drawn to recent major critiques of Cattell's ‘16 PF’ model of personality. Various six/seven-factor models of personality (assuming intelligence is included) derived from the 16 PF or its precursors are described. The equation of Eysenck's E and N factors with Cattell's second-order factors of ‘exvia’ and ‘anxiety’ is mentioned. An examination is made of the problems of factored scale construction and the ‘number of factors’ issue, especially when item responses are analysed.Three previous second-order factor solutions to the HSPQ are presented. These show a remarkable degree of concordance among themselves and with an item analysis of the HSPQ conducted by the writers. This item analysis also reveals serious doubts about the primary trait structure proposed by Cattell and Cattell (1969). It is suggested that, for adolescents, the four studies, with some support from the 16 PF analyses, point to a six-factor structure for personality consisting of anxiety ( = Eysenck's N); tender-tough-mindedness ( = Eysenck's Psychoticism); carefulness-casualness and two aspects of extraversion-introversion: (a) preference for working with people rather than with things. (b) Classical extraversion (the last or both (a) and (b) being analogous to Eysenck's E) and finally intelligence, if this can be classified as an aspect of personality.     

Extraversion and Arousal Procrastination: Waiting for the Kicks

Procrastination is a prevalent and complex psychological phenomenon that has been defined as the purposive delay in beginning or completing a task. Given the potential implications for a broad range of situations, including both academic performance and safety sensitive occupations, it seems reasonable and judicious to systematically examine this phenomenon. While there is growing interest in procrastination, our understanding of underlying explanatory factors remains quite limited. Eysenck’s (1967) theory of personality, and in particular his biologically-based theory of extraversion, could shed light on this phenomenon. The purpose of this paper was to examine the relationship between extraversion and arousal procrastination. In accordance with Eysenck’s theory that extraverts tend to seek external sources of arousal, it was hypothesized that they would be more likely than introverts to engage in arousal procrastination. Participants completed a series of counterbalanced questionnaires measuring extraversion and procrastination. Results indicated that extraversion significantly predicted the engagement in this type of procrastination. Limitations, implications, and future research are discussed.     

Personality,time of day and delayed memory for tv news

An experiment was conducted to test the effects of time of day on delayed memory for televised news stories. Three groups received the same sequence of 6 news stories at 09.30, 13.30 and 16.30, respectively. Unexpected tests of free recall, cued recall and recognition were given about 2 hr after news presentation. Results showed that memory performance improved slightly across the day on tests of recall, and significantly so on recognition. Personality differences were also examined. In general, introverts remembered more than extraverts and differences between them were most marked during the late-afternoon session especially on free recall and when minimal cuing was provided. The results support previous time-of-day findings for delayed retention of complex learning materials. Personality differences observed here are consistent with predicted introvert-extravert differences in memory performance predicted by Eysenck's modified action-decrement hypothesis.     

Personality and the topography of the conditioned eyelid response

One-hundred and four women were tested on an eyelid conditioning paradigm in a 2 x 2 x 2 factorial design where two levels of US intensity (1 vs 3 p.s.i.) were balanced against two rest pause interpolations (after 25 and after 50 trials), and the presence or absence of a warning stimulus prior to CS-US presentation. Subjects were later classified as high, low or intermediate extraverts on the basis of a personality questionnaire. A very detailed analysis of conditioned responses was carried out, using both simple and composite measures including work-ratio, utility-ratio, CR frequency, peak latency, peak amplitude, response area and effective response area, degree of avoidance amplitude and latency, etc. Major findings related to similar effects of high intensity US vs low intensity US, and introversion vs extraversion; introverts react as if they were responding to more intense stimuli than extraverts. This finding cuts across other parameter variables, and supports Eysenck's formulation of personality-conditioning relationships in terms of higher cortical arousal in introverts as compared with extraverts.     

Field-dependence,extraversion, Eysenck and autarky

The research literature was examined with regard to relationships between Field-dependence and Extraversion. Eysenck's contention that the two variables are significantly related to an extent justifying the use of causal hypotheses based on extraversion theory to account for field-dependent behavior was not supported.     

Color preferences, extraversion, and neuroticism of art students.

Color preferences of 190 art students (G?tz & G?tz, 1974, 1975) were compared with the corresponding scores on extraversion (E) and neuroticism (N). It was found that the preferences of a group of 27 highly gifted young artists were different from preferences of average and less gifted Ss who had little or no artistic practice. In the latter group extraverts and ambiverts mainly preferred primary and secondary colors (light clear and dark clear tones included), while introverts preferred tertiary colors (earth colors) and achromatics. However, in the group of highly gifted Ss no significant differences between positive and negative rankings in both color categories were found. Neuroticism had no effect on color preferences; this holds for introverts and extraverts and for each single color.     

Properties of the diffuse thalamocortical system and human personality: A direct test of Pavlovian/Eysenckian theory

Advances in the last few decades demonstrate the relevance of Pavlov's classification of behavioural types with respect to human individual differences and suggest that the hypothetical excitatory and inhibitory processes which he associated with these differences correspond to cortical and thalamic neuron populations of the diffuse thalamocortical system (DTS). Since the transmission properties or time constants of these DTS elements would correspond to the Pavlovian property of ‘strength’, and since they can be evaluated in human subjects (Robinson, 1981), it is possible to formulate hypotheses based on the fundamental principles of strength and balance which Pavlov employed to provide a causal explanation for temperamental types. A major finding is that covariation of the time constants equated with strength correlates 0.95 with covariation of extraversion and stability scores on the Eysenck Personality Questionnaire (EPQ). This result provides unequivocal support for the relationship between human individual differences and properties of the nervous system postulated by Pavlov and it also confirms the neurophysiological underpinning of Eysenck's influential theory of human personality. In addition, the relationship between Pavlovian and Eysenckian concepts is clarified and EEG parameters are meaningfully related to personality differences.     

Psychopathy,anxiety and malingering

Psychopathy is commonly measured as a low score on an Anxiety scale or as a high score on the MMPI Pd scale. The Pd scale, the Spielberger et al. Trait Anxiety scale and a short Achievement Motivation scale were administered to a random postal sample of 115 Australians. It was found that there was a high positive correlation between the Pd and Anxiety scales. This strongly supports Eysenck's theory that psychopaths are neurotic extraverts. A possible alternative explanation of the findings, however, is that the Pd scale may measure not psychopathy but malingering.     

Positive evidence for Eysenck’s arousal hypothesis: A combined EEG and MRI study with multiple measurement occasions

Eysenck’s arousal hypothesis suggests that introverts have greater cortical activity than extraverts. This prediction was tested in several studies that used the electroencephalogram (EEG) alpha activity to index cortical arousal, but empirical findings are inconsistent. Possibly, external factors of the measurement situation or static factors such as skull thickness may act as nuisance variables on alpha activity and thus mitigate the relation between arousal and extraversion. The aim of the present study was to test the arousal hypothesis with a focus on these methodological issues. Resting EEG was acquired on several occasions of measurement, skull thickness was quantified with anatomical magnetic resonance imaging (MRI), and extraversion was assessed by questionnaire. There was a positive association between alpha activity and extraversion, which was neither affected by external factors nor by skull thickness. This finding is in line with the arousal hypothesis and suggests that external or static factors do not contribute to the inconsistency of empirical findings.     

Differential relationships of extraversion,impulsivity, and sociability to study habits

Reanalysis of data on library study habits presented by J. B. Campbell and C. W. Hawley (Journal of Research in Personality, 1982, 16, 139–148) revealed differential utility for the EPI extraversion scale and its components, impulsivity and sociability. Individuals studying in locations that provided greater external stimulation had significantly higher extraversion and impulsivity, but not sociability, scores than individuals studying elsewhere in the library. Impulsivity was more strongly associated than sociability with preferred noise levels, frequency of study breaks, and importance and preferred levels of socializing opportunities, but less strongly associated with preferred levels of crowdedness. Findings are discussed in terms of the interpretation, reliabilities, and theoretical context of the subscales.     

Activity measures in stress-attenuated novelty tests as possible analogues for extraversion in rats: Some experimental results

In an attempt to extend and validate Garcia-Sevilla's (1974) hypothesis proposing ambulation in a non-stressful open field (OF) as an animal analogue of human extraversion, ambulatory behaviour and rearing behaviour were studied and compared in several experiments with genetically-unselected rats. The effects of variation of OF auditory stimulation level, the correlation with a two-way avoidance-learning situation and the effects of a stimulant dose of d-amphetamine and an anxiolytic one of diazepam upon rearing and ambulatory behaviours were studied. All in all, our results support some of the requirements of the hypothesis, but also generate some additional problems. The results show that the number of rearings could be a better and more sensitive measure of variations in the level of arousal and a better predictor of shuttle-avoidance conditioning than ambulation. However, all activity measures are at least moderately intercorrelated, and they become grouped when results are factor analysed. All the results are discussed with reference to Eysenck's personality theory and Gray's anxiety theory, and it is concluded that these measures are too multidetermined and too poorly controlled to represent correctly and in a direct form a personality dimension such as Extraversion. Anyway, this attempt could be a good point of departure for discovering more efficient animal behavioural measures of arousability.     

Values and personality: a survey of their relationship in the case of juvenile delinquece

Attempts to verify Eysenck's theory of criminality have usually been concerned with the proportion by which delinquents differ from non-delinguents on the dimensions of extraversion, neuroticism and psychoticism. There are very few studies concerned with the proportion in which these dimensions are related to the acquisition of moral or social rules, the real core of this theory. The current study examines the theory from a new approach, trying to show in what measure the value priorities of a group of 113 juvenile delinquents are related to the personality dimensions stated by Eysenck.     

Extraversion-introversion and heat-stress tolerance

Ten Ss were tested under heat-stress conditions, during which their physiological stress was measured. Before commencement of the experiment, the Ss' level of extraversion was measured, as well as the meaning they assigned to the situation and the subjective probability of success they gave themselves. It was found that extraverts assigned significantly more positive meaning to the heat-stress situation than introverts, and they tended to estimate their probability of success as higher than did the introverts. However, extraverts tended to suffer from higher physiological stress than introverts, where the main cause for that seemed to be their higher expectations resulting from the positive meaning assigned by them to the heat-stress situation.