Differences in the transmission of sensory input into motor output between introverts and extraverts: Behavioral and psychophysiological analyses

The present study was designed to investigate extraversion-related individual differences in the speed of transmission of sensory input into motor output. In a sample of 16 introverted and 16 extraverted female volunteers, event-related potentials, lateralized readiness potentials (LRPs), and electromyogram (EMG) were recorded as participants performed a visual choice reaction time task. As additional behavioral indicators of performance, measures of reaction time (RT) and response dynamics were obtained. Although extraversion-related differences were found neither for behavioral measures nor for the N1 and P3 components of the evoked potential, introverts showed a reliably shorter latency in stimulus-locked LRP than extraverts. This latter finding supports the notion of faster stimulus analysis in introverts compared to extraverts. Furthermore, there was no indication of extraversion-related individual differences in speed of response organization and response execution as indicated by response-locked LRP and EMG latencies, respectively. However, a significantly higher EMG amplitude observed with introverts pointed to a less accurately adjusted motor output system of introverts compared to extraverts.     

Individual differences in components of slow cortical potentials: implications for models of information processing

Individual differences in the effects of pharmacological and behavioural manipulations on slow cortical potentials (SCP), may reflect personality differences in type of informational control under attentional stress. Two experiments were conducted to examine SCP component differences in extraverts and introverts under different attentional tasks and with and without nicotine smoking ‘stressor’ conditions. In an initial experiment a decrease in late negativity for introverts and an increase in late negativity for extraverts suggested that smoking enhanced introverts' stimulus set and extraverts' motor set. In a second experiment, personality differences in SCP were examined again, but within a signal-detection paradigm, which allows separate assessment of the contribution of sensory sensitivity and response bias factors to performance. Smoking increased sensitivity in both personality groups, but response bias (caution) increased in introverts only. Extraverts showed an increase in central negativity during smoking whilst introverts showed a decrease in negativity and a decrease in positive wave components. The results are explained in terms of a motor model of attentional control whereby smoking regulates inhibitory controlled actions in introverts, but activates general motor processes for extraverts.     

Extraversion, attention, and habituation of the auditory evoked response

Short-term changes in the auditory evoked response to low-frequency tones (0.5 kHz, 80 dB) were examined for independent groups of introverts and extraverts under attend and ignore conditions. Introverts displayed greater N1-P2 amplitude than extraverts to the first stimulus in a four-stimulus train. The N1-P2 amplitude differences between introverts and extraverts could not be attributed to differences between the groups in either habituation or attention processes. Overall, the effect is indicative of the introverts' enhanced sensitivity to physical stimulation.     

Reaction to punishment, reflectivity, and passive avoidance learning in extraverts

Passive avoidance learning occupies a central role in accounts of disinhibited behavior, ranging from psychopaths' persistent criminality (Hare 1970) to extraverts' gregariousness (Gray, 1972). To explore the mechanism underlying passive avoidance deficits, we assessed the relation of extraversion, neuroticism, and response latency after punishment to passive avoidance learning by using two successive go/no go discrimination tasks. The tasks were designed to examine two aspects of subjects' reactions to punishment: response speed on trials immediately following punishment (Experiment 1) and time to terminate punishment feedback between successive trials (i.e., reflectivity; Experiment 2). Consistent with previous findings, the results of Experiment 1 showed that extraverts commit more passive avoidance errors than introverts do (Newman, Widom, & Nathan, 1985) and fail to pause following punished errors (Nichols & Newman, 1986). In Experiment 2, only neurotic extraverts displayed this pattern of performance differences. In both experiments, longer pausing following punishment predicted better learning from punishment for both introverts and extraverts. These results suggest that, in the presence of salient cues for reward, extraverts' characteristic reaction to punishment interferes with processing punished errors and may contribute to their more general propensity for impulsive, nonreflective action.     

Simple visual reaction time,personality and strength of the nervous system: A signal-detection theory approach

Eysenck (1967) has reviewed evidence which suggests that introverts have a higher level of arousal than extraverts. Moreover, Gray (1967) has proposed that introverts have weak nervous systems, in the Russian terminology. Studies of simple reaction time such as that of Mangan and Farmer (1967) have posed problems for these views, but it is suggested that this may have been due to criterion differences between introverts and extraverts. In the present study a simple visual reaction-time task and a signal-detection task were conducted side by side. No significant differences between introverts and extraverts were found in measures of strength derived from the former, or measures of criterion derived from the latter. However, high N Ss were found to have a significantly lower value for Nebylitsyn's index of the slope of the reaction time/stimulus intensity function, thus supporting the view that high N Ss have relatively weak nervous systems.     

Memory scanning,introversion-extraversion,and levels of processing

Individual differences in information processing were studied in the form of the hypothesis that arousal, as indexed by a personality measure of introversion-extraversion, affects the speed with which certain kinds of processing are completed. The Sternberg paradigm was used, and the results suggested that introverts and extraverts scanned for physical features equally rapidly, but that introverts were slower than extraverts at scanning for the semantic features of category membership. There was limited support for the hypothesis that introverts, thought to be more aroused than extraverts, are less able to engage in shared or parallel processing. It was concluded that information processing in introverts and extraverts may differ qualitatively as well as quantitatively.     

Overhabituation and dishabituation: Effects of extraversion and amount of training

The Eysenck (1967) hypothesis that introverts have higher levels of cortical activation than extraverts has received support in a number of psychophysiological studies, though there is not complete consistency. The present study extended the habituation paradigm used in some previous work to include an examination of differences between extraverts and introverts during and following long-term overhabituation. Electrodermal activity was recorded while 72 extraverts and 72 introverts were subjected to criterion auditory habituation to a 1000-Hz, 90-db tone, followed by 60, 100, or 140 trials of overhabituation. The overhabituation run was followed by a test stimulus of 7000 Hz and a final repetition of the standard stimulus. Results showed that introverts increased in response frequency with increasing overhabituation exposure, while extraverts showed an increase only from 100 to 140 trials. In addition, the hypothesis that differences in test response amplitude favoring introverts would be eliminated by extended overhabituation training was supported. Specifically, extraverts showed increased responses at 100 and 140 trials, while introverts remained approximately constant across the three conditions. Finally, results supported the Sokolov hypothesis that overhabituation training produces test responses of larger amplitude.     

Incentive and feedback effects on target detection: A chronometric analysis of Gray's model of temperament

Chronometric (i.e. reaction time) techniques were used to investigate the response, arousal, and attentional components of Gray's (1971, 1982) model of temperament. Subjects were tested in a game context, where each trial consisted of an incentive warning signal (positive or negative), a visual detection target (left or right visual field), and a feedback signal (positive or negative). Several findings were consistent with Gray's proposal that extraverts tend to respond impulsively given signals of reward whereas introverts respond with inhibition given signals of punishment. Extraverts made more overall errors than introverts in the first experiment, and more errors following positive incentive signals in the second study. In addition, introverts responded more slowly than extraverts following negative feedback in the first study. Evidence was also found in support of Gray's proposal that introverts allocate more attention to negative cues than extraverts. Following negative feedback, introverts showed a reflexive attentional bias in favor of negative locations in the second experiment. However, no support was found for the temperamental differences in phasic arousal suggested by Gray's model. The magnitude and build up of general alerting effects following positive and negative incentives were similar for introverts and extraverts.     

Introversion-extraversion: the Bell-Magendie law revisited

Evidence from several sources, including psychophysical, electrodermal and evoked potential measures, indicates that introverts display an enhanced response to sensory stimulation. There is also evidence, primarily from psychophysical studies, which suggests that extraverts may be disposed to emit short, strong bursts of motor activity which facilitate performance on tasks that involve gross motor activity but which impede performance on tasks which require refined motor control. The present paper develops an argument in which the differences between introverts and extraverts in the response to sensory stimulation and in the expression of motor activity may be referred to differences at the level of the sensory and motor nerve.     

认知操作、认知方式与外倾性人格特质的关系

对28名外倾被试和28名内倾被试进行实验性认知测试,以考察认知操作、认知方式与外倾性人格特质的关系。结果表明,内外倾被试在含有社会认知操作、非社会认知操作的认知任务的测试总分上没有差异,而在社会认知一非社会认知方式的评价分数上存在显著差异。外倾被试更多地倾向于社会认知型认知方式,内倾被试更多地倾向于非社会认知型认知方式。研究结果支持了外倾性与智力关系的假设：外倾性与社会认知一非社会认知的认知方式存在相关关系,而与认知操作测试总分无关。     

Psychological refractory period in introverts and extraverts

The present study was designed to explore extraversion-related differences in the psychological refractory period (PRP). PRP refers to a bottleneck of information processing that becomes evident when participants are required to respond to two signals (S1 and S2) presented in rapid succession. If this capacity limit of premotor information processing is essential for differences in speed of information processing between introverts and extraverts, magnitude of the PRP effect should vary as a function of extraversion. Due to the failure of previous attempts to establish extraversion-related differences in the PRP effect, we also obtained lateralized readiness potentials (LRPs). For this purpose, 63 introverted and 63 extraverted female participants were tested with a standard PRP design. Extraverts responded faster to S2 and exhibited shorter stimulus-locked LRP latencies compared to introverts. Although a general PRP effect could be shown at the behavioral and psychophysiological level, there was no indication for any extraversion-related differences in PRP. Thus, extraversion-related differences in speed of information processing at the premotor level appear unlikely to originate from individual differences in the capacity limits underlying the PRP phenomenon. Furthermore, our findings provide converging evidence for the notion that extraversion-related individual differences in processing speed depend on specific task demands.     

Biological Bases of Extraversion Psychophysiological Evidence

There is a good deal of evidence, particularly from electrodermal and electrocortical recording procedures, that introverts exhibit greater reactivity to sensory stimulation than extraverts. There is little evidence that introverts and extraverts differ in base level of arousal in neutral conditions, and there is no clear evidence that their differences in sensitivity to stimulation are determined by differences in attentional state. Faster auditory brainstem evoked response latencies observed for introverts implicate differences in peripheral sensory processes that are not determined by mechanisms in the reticular system as proposed in the arousal hypothesis. There is also evidence that individual differences in the expression of motor activity between introverts and extraverts involve differences in motoneuronal excitability.     

Introversion-extraversion,tempo, and guided imagery

This research tested the hypotheses that (a) introverts would produce more vivid imagery than would extraverts, and (b) introverts would produce better mental imagery if the background auditory tempo was slow, and extraverts would produce better mental imagery of the background auditory tempo was fast. Participants (N=240) were classified as introverts or extraverts and were randomly assigned one of three tempo conditions: slow, fast, or none. They were instructed to form mental images while listening individually to one of two stories. Clicks (slow or fast) sounded in the background during the stories. All participants then completed detailed questionnaires about the vividness of their mental imagery. Analysis showed that introverts reported significantly more vividness in their imagery than did extraverts. The hypothesized interaction between personality and tempo was not found. Implications were drawn for therapeutic applications of mental imagery.     

Attention and personality in augmenting/reducing of visual evoked potentials

Earlier research has shown that extraverts tend to increase their visual evoked potential amplitudes with increasing light intensity (augmenting), while introverts reach their maximum amplitude at lower intensities (reducing). The evoked response has normally been measured from association areas of the brain (at the vertex). The present study measured VEP amplitudes over visual cortex and at the vertex, using four light intensities in two conditions, where attention was either directed towards the light stimuli, or away from them by a concurrent auditory task. Forty subjects were classified as extraverts or introverts based on the Eysenck Personality Inventory. The results show that attention interacted significantly with extraversion. Introverts exhibited a narrower focus of attention, while higher amplitudes and amplitude-intensity functions when attending to the light flashes and lower when distracted. Extraverts showed smaller differences between conditions, indicating a more evenly distributed attention. Higher arousal in introverts is the probable cause of their narrower focus of attention. There were marked differences in the distribution of activity between vertex and occipital cortex. Introverts showed relatively stronger occipital responses and extraverts stronger vertex responses across all intensities and in both conditions. The predisposition for mainly perceptual responses to aversive stimuli in introverts, and for general alerting and motor preparatory responses in extraverts, are interpreted as supportive of Brebner and Cooper's hypothesis that introverts are ‘geared to inspect’ and extraverts are ‘geared to respond’.     

Music while you work: the differential distraction of background music on the cognitive test performance of introverts and extraverts

The current study looked at the distracting effects of ‘pop music’ on introverts' and extraverts' performance on various cognitive tasks. It was predicted that there would be a main effect for music and an interaction effect with introverts performing less well in the presence of music than extraverts. Ten introverts and ten extraverts were given two tests (a memory test with immediate and delayed recall and a reading comprehension test), which were completed, either while being exposed to pop music, or in silence. The results showed that there was a detrimental effect on immediate recall on the memory test for both groups when music was played, and two of the three interactions were significant. After a 6-minute interval the introverts who had memorized the objects in the presence of the pop music had a significantly lower recall than the extraverts in the same condition and the introverts who had observed them in silence. The introverts who completed a reading comprehension task when music was being played also performed significantly less well than these two groups. These findings have implications for the study habits of introverts when needing to retain or process complex information. © 1997 John Wiley & Sons, Ltd.     

Extraversion,neuroticism and individual differences in event-related potentials

Event-related potentials (ERPs) in response to task-irrelevant tone pips were elicited during meaningful and meaningless speech passages for two groups of subjects selected on the basis of their scores on the extraversion-introversion scale of the Eysenck Personality Questionnaire, ERPs were recorded from two temporal (T3 and T4) and Wernicke (W1 and W2) scalp locations. Peak latencies and amplitudes of N1, P2 and N2 components were obtained for each subject during each meaningful and meaningless condition. The extraverts exhibited higher levels of subjective engagement in the meaningful-speech condition than in meaningless condition; the opposite trend was found for introverts. The extraverts showed greater N2 amplitude in the meaningful-speech condition than in the meaningless condition; the reverse trend across conditions was found for introverts.     

The influence of introversion/extraversion on the skin conductance response to stress and stimulus intensity

A series of studies compared skin conductance level (SCL) for introverts and extraverts during a series of tones varying in both stimulus intensity (SI) and the amount of stress preceding the tones. When a difficult paired-associate task preceded the tones, both groups were about the same for 83 dB tones but extraverts were much higher at 103 dB, introverts failing to show an increase as a function of SI. There were no differences between the two groups following a simple paired-associate task, both groups showing a similar increase with increased SI. Finally, SCL was higher for introverts than extraverts during tones preceded by a rest period, and this was especially true for the early trials and for lower SI (75 and 83 dB compared with 100 and 103 dB). Taken together, these results suggest that SCL is higher for extraverts at higher levels of arousal but that the reverse is true for lower levels of arousal. This relationship is consistent with the theory that introverts have a “weak nervous system” which develops transmarginal or protective inhibition under stress.     

Extraversion-introversion and time perception

The relationship between stimuli complexity extraversion-introversion and time perception was tested. It was found that extraverts estimated the exposure duration of simple figures to be longer compared to introverts and that this discrepancy vanished in regard to complex figures. The findings were explained in terms of Hogan's (1978) model and on the basis of differential utilization of cognitive mechanisms for time perception by extraverts and introverts.     

Expectation of success following noncontingent punishment in introverts and extraverts

Recent findings indicate that extraverts are more likely than introverts to continue responding in the face of punishment and frustrating nonreward (Newman & Kosson, 1984; Tiggemann, Winefield, & Brebner, 1982). The current study investigates whether extraverts' expectations for success are, similarly, resistant to interruption and alteration. To test this hypothesis, 50 introverted and 50 extraverted male undergraduates were exposed to pretreatment with either a 50% level of noncontingent reward or a 50% level of noncontingent punishment. As predicted, there were significant Group X Pretreatment interactions on all dependent measures. In comparison to those introverts who received the punishment pretreatment, extraverts exposed to the same pretreatment placed larger wagers on their ability to succeed, and reported higher levels of perceived control. In addition, relative to their estimates for the pretreatment task, extraverts exposed to noncontingent punishment increased their expectation for success, whereas introverts exposed to noncontingent punishment decreased their performance expectations. No differences were observed between the two groups following pretreatment with noncontingent reward. The results suggest that extraverts are characterized by a distinctive reaction to punishment involving response facilitation as opposed to response inhibition.     

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.