An event-related potential analysis of extraversion and individual differences in cognitive processing speed and response execution.

Individual differences in cognitive processing speed and response execution were examined in relation to extraversion. Event-related potentials (ERPs) were recorded concurrently with reaction time and movement time (MT) measures as participants (iNn?=?67) performed simple reaction time and stimulus–response compatibility tasks. Slower processing speed for extraverts, as indicated by longer latency of a late positive ERP wave, P3, was only evident in conditions in which stimulus information was in conflict with response selection demands. As previously reported, the salient effect in all conditions of both tasks was faster MT for extraverts, an effect that is indicative of differences in fundamental motor processes. On the simple reaction time task, amplitudes of the N1 component, an early negative ERP wave, were smaller for extraverts than for introverts in response to auditory tones, an effect that affirms the enhanced sensory reactivity of introverts to punctate physical stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in rate of affect change: Studies in affective chronometry.

Three studies explored individual differences in rate of affect change. Participants watched affect-inducing videos and reported their affect twice in 20 min. Individual differences in rate of affect change emerged independently of initial affect intensity and stress appraisals, revealing 2 affect-change profiles. Positive affect augmenters (extraverts, emotionally stable participants, and those with high negative mood regulation expectancies) showed slow rates of positive and rapid rates of negative affect decay. Negative affect augmenters (introverts, neurotics, and participants with low negative mood regulation expectancies) showed slow rates of negative and rapid rates of positive affect decay. These findings expand the literature on affective style, have adaptational implications, and highlight future research directions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subjective effects of caffeine among introverts and extraverts in the morning and evening.

In previous studies of psychomotor performance, the stimulant effects of caffeine differed by personality characteristics. For example, caffeine improved the task performance of extraverts but overaroused introverts and thus impaired their performance. The present study compared the effects of caffeine on subjective arousal among introverts and extraverts. Seventeen introverts and 19 extraverts drank coffee that contained doses of 0, 2, and 4 mg/kg caffeine during morning and evening sessions in a within-subjects, randomized, double-blind, crossover design. At 30-min intervals for 180 min after drinking, participants completed the Profile of Mood States, a battery of self-report visual analog scales, and the Digit Symbol Substitution Test (DSST). Caffeine effects on mood and task performance did not significantly interact with extraversion, except for nonsignificant trends for caffeine to increase happiness and vigor more among extraverts than introverts. No 3-way interactions of group, time, and dose were found on any scales or on the DSST. Results do not support the hypothesis that caffeine differentially affects extraverts and introverts, particularly at different times of the day. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of punishment on response latency in extraverts.

Previous findings indicate that in comparison to introverts, extraverts are prone to form responses that are resistant to interruption by punishment. Because the tendency to stop and reflect following punishment may be crucial for subsequent learning, the present study examined differences between introverts' and extraverts' reactions to punishment using response latency on the trial following punishment as the dependent variable. 66 extraverted and 66 introverted male undergraduates, selected on the basis of Eysenck Personality Questionnaire scores, performed a pattern-matching task in which they received noncontingent 50% success and 50% failure feedback under 3 incentive conditions: reward only, punishment only, or both. As predicted, a significant interaction was found in the both incentive condition, reflecting the tendency of extraverts to respond more quickly and introverts more slowly following punishment than reward. No significant effects were found in the other 2 conditions, although extraverts tended to respond more quickly overall when only reward was given. A 2nd experiment, with 101 male undergraduates, that used reward-only and punishment-only feedback replicated this finding and yielded a significant group?×?condition interaction. Results indicate that in contrast to introverts, extraverts are activated by the availability of reward and, paradoxically, that punishment may facilitate rather than interrupt extraverts' reward-seeking behavior. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperament and attention: Orienting toward and away from positive and negative signals.

Two studies used a target detection task to examine temperament-related attentional biases toward and away from significant stimuli. Pretarget cues were used to orient attention to locations carrying a positive incentive value (where points could be gained) or a negative value (where points could be lost). Under both involuntary and voluntary conditions, extraverts were slow to shift attention away from positive locations, whereas introverts were slow to shift from negative locations. These biases were enhanced on trials following negative feedback and tended to be strongest in Ss high in Neuroticism. The findings support models proposing that Extraversion reflects the combined activity of positive (strongest in extraverts) and negative (strongest in introverts) incentive motivational processes. They further suggest that incentive processes regulate the ability to shift attention away from, rather than toward, significant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Double Dissociation Between Mood States and Personality Traits in the Anterior Cingulate.

Neuroticism and extraversion are personality traits associated with negative and positive mood states, respectively, confounding trait and state factors that may affect brain responses to emotional stimuli. The authors dissociated these factors using fMRI and the emotional Stroop attention task: Anterior cingulate (AC) response to positive stimuli varied as a function of personality trait, but not mood state, whereas AC response to negative stimuli varied as a function of mood state, but not personality trait. Negative mood, but not personality trait, also increased the functional connectivity between AC and other regions. Variance in AC activation can thus be ascribed to an intersubject variable (extraversion) when responding to positive stimuli and an intrasubject variable (mood) when responding to negative stimuli. The former may explain stable differences between extraverts and introverts. The latter may provide an adaptive mechanism to expand an individual's dynamic range in response to potentially dangerous or threatening stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of induced moods on voice affect.

Happy or sad moods were experimentally induced in 30 1st, 3rd, and 5th graders using a frequently employed mood-induction technique. Voice affect (with verbal content filtered out) was found to be significantly happier during the positive mood induction than during a baseline neutral condition. Voice affect was significantly sadder during the negative mood induction only for the youngest age group (1st graders). Results support the validity of mood-induction techniques with young children. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The epistemic benefits of trait-consistent mood states: An analysis of extraversion and mood.

One must consider both trait and state affect to predict individual differences in emotional processing. The present results document a novel trait-state interaction that is consistent with proposals concerning the epistemic functions of affect (A. R. Damasio, 1994). Four studies tested the effects of extraversion and mood on motivation-relevant processing. Study 1 measured naturally occurring mood, whereas Studies 2-4 manipulated mood. Extraverts were faster to link events to their personal motivations when in a positive mood state, whereas introverts were fast to do so in a neutral or negative mood state. Further findings indicate that this interaction affects attitude accessibility rather than event elaboration. Overall, the authors suggest that there are pragmatic benefits to trait-consistent moods, particularly for processing motivation-relevant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in entrainment of mood to the weekly calendar.

This study addressed two questions: Do daily fluctuations in mood exhibit a 7-day (circaseptum) cycle, and are there reliable individual differences in how entrained peoples' moods are to such a weekly cycle? Spectral analysis of daily mood over 84 occasions revealed a strong weekly rhythm in the temporal organization of mood in a sample of 74 undergraduates. A sine wave with a period of 7 days accounted for 40% of the variance in the daily mood data. Individual differences were also found in how entrained subjects' moods were to this weekly rhythm. We predicted that extraverts (compared with introverts) should be less entrained to a weekly cycle. Results suggest that the novelty- and sensation-seeking behavior of extraverts most likely serves to lessen the cyclical predictability of their day-to-day moods. The origin and psychological meaning of the 7-day week are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the effects of introversion-extraversion and anxiety of conditoning.

This study investigates the effects of Eysenck's introversion-extraversion theory and Spence-Taylor's concept of anxiety on the eyeblink conditioned response by varying these factors independently. 56 patients were subjected to conditions of high and low anxiety. Group I (anxious group) were about to undergo major surgery; Group II (nonanxious group) were patients who had successfully recovered. These patients were divided into high introverts and high extraverts, yielding 4 groups (anxious introverts anxious extraverts, nonanxious introverts, nonanxious extraverts). The anxious groups showed greater conditioning than the nonanxious groups and no significant differences were found between the high and low introvert groups, supporting the hypothesis that total drive is, in part, a function of internal anxiety. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personality and placebo effects upon timing behavior.

4groups of Ss, scoring in the extremes of Neuroticism and Extraversion scales, participated in 3 sessions of 100 learning and 25 extinction trials of timing behavior. ? of the Ss of each group took a placebo at Session 2, the other ? at Session 3. A repeated measurement, 2 X 2 Latin square design, was incorporated. Accuracy was significantly greater for Low than High neurotics during reinforcement trials. Accuracy significantly decreased for High neurotic introverts and increased for the High neurotic extraverts, and Low neurotic introverts and extraverts groups. Under placebo conditions, introverts' accuracy was significantly greater than extraverts'. High neurotic introverts were considered positive placebo reactors, and High neurotic extraverts were negative placebo reactors. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Size constancy as a function of personal adjustment and disposition.

"A size-distance judging task was given to 40 men who were classified in 4 groups, respectively styled 'neurotic introverts,' 'neurotic extraverts,' 'normal introverts,' and 'normal extraverts.' Analysis of data from 4 distances under 2 conditions of judgment, i.e., objective and analytic, indicated that neuroticism was the major source of between-group variation. Under analytic conditions, neurotic persons tended to match the stimulus in terms of visual angle, and normals in terms of size." 15 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Understanding extraverts' enjoyment of social situations: The importance of pleasantness.

Extraversion is a broad, multifaceted trait, yet researchers are still unsure of its defining characteristics. One possibility is that the essential feature of extraversion is the tendency to enjoy social situations. An alternative possibility is that extraversion represents sensitivity to rewards and the tendency to experience pleasant affect. In three studies, participants rated situations that varied on two dimensions: (a) whether they were social or nonsocial and (b) whether they were very pleasant, moderately pleasant, moderately unpleasant, or very unpleasant. Extraverts only rated social situations more positively than introverts did when the situations were pleasant, and extraverts also rated nonsocial situations more positively than introverts did if the situations were pleasant. Thus, the pleasantness of situations was more important than whether they were social or nonsocial in determining extraverts' and introverts' enjoyment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preferred stimulation levels in introverts and extroverts: Effects on arousal and performance.

In 2 experiments, 70 extraverted and 70 introverted (Edwards Preference Inventory) males either chose the level of intensity of noise to be heard during a paired-associates (PA) learning task or were assigned noise at a given level of intensity. In both experiments, extraverts chose more intense noise levels than introverts. Extraverts and introverts were equal in psychophysiological arousal when stimulated with noise of an intensity chosen by either themselves or yoked members of the same personality classification. Introverts were found to be more aroused than extraverts when compared at the same intensity, regardless of whether the intensity was one preferred by extraverts or one preferred by introverts. At very high and very low levels of intensity of noise stimulation, introverts and extraverts were equally aroused in the 2nd experiment. In both experiments, PA learning was best among introverts and extraverts who were stimulated at a level of intensity chosen by themselves or members of the same personality classification. Results are discussed in terms of Yerkes-Dodson Law and its relation to extraversion–introversion. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of cognitive load on self-presentation: Can cognitive busyness help as well as harm social performance?

Extra cognitive loads can hinder challenging self-presentations by usurping needed cognitive resources but also may sometimes improve them by shifting attention away from negative self-preoccupation. In Study 1, extraverts and introverts participated in an interview in which they presented themselves as either extraverted or introverted. Congruent self-presentations, which should be cognitively nondemanding, were unaffected by a cognitive busyness manipulation (rehearsing an 8-digit number). However, incongruent self-presentations were affected by busyness. Busyness decreased the effectiveness of extraverts; who tried to appear introverted but increased the effectiveness of introverts who tried to appear extraverted. Study 2 found that introverts, who also tend to be socially anxious, reported less public self-consciousness and fewer negative self-focused thoughts when they were busy than when they were not busy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Introversion-extraversion and kinesthetic aftereffects.

"Eysenck's hypothesis that extraverts show greater figural aftereffects than introverts was investigated by comparing the kinesthetic aftereffects of 37 subjects with high scores on Guilford's Rhathymia scale (extraverts) with those of 37 subjects with low scores on the scale (introverts). The personality groups did not differ significantly in amount of aftereffect. Several differences remain between the present study and Eysenck's earlier one, but the generality of the hypothesis that extraverts develop greater aftereffects than introverts is seriously questioned." From Psyc Abstracts 36:02:2HE95R. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Introverts' and extraverts' responses to nonverbal attending behavior.

Examined the different responses of 52 male undergraduate introverts and extraverts (as determined by the Extraversion scale of the Eysenck Personality Questionnaire) to 2 types of helper nonverbal attending. One half of the Ss viewed a listener intensely attending (leaning forward) and one half viewed the listener in an upright position. Results indicate that (a) introverts rated the listener higher than did extraverts, independent of his posture; (b) the listener in the forward attending posture was viewed by all participants as more attentive; and (c) the extraverts who viewed the listener in the upright position rated him as more threatening than did the introverts in either condition or the extraverts viewing the listener in the forward position. In no case was the listener in the forward attending posture rated more negatively than the listener sitting upright. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Qualitative analysis of the performance of introverts and extraverts on Standard Progressive Matrices

The present study was designed to bring out the differences between extraverts and introverts on Standard Progressive Matrices. A group of 100 subjects of equal number of sexes were given a qualitative analysis of their performance on SPM. The study brought out the initial superiority of extraverts over introverts. But with passage of time and increase in difficulty level the introverts did significantly better as shown both by the t-ratios and the F-ratios. Personality interacted with sex to yield differences in performance of wrong scores only. These findings were discussed in terms of arousal, cortical excitation and reactive inhibition.     

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. To test whether extraverts' expectations for success are similarly resistant to interruption and alteration, 50 introverted and 50 extraverted male undergraduates (as assessed on the Eysenck Personality Questionnaire) 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 by pretreatment interactions on all dependent measures. In comparison to 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 2 groups following pretreatment with noncontingent reward. Results suggest that extraverts are characterized by a distinctive reaction to punishment involving response facilitation. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why introverts can't always tell who likes them: Multitasking and nonverbal decoding.

Despite personality theories suggesting that extraversion correlates with social skill, most studies have not found a positive correlation between extraversion and nonverbal decoding. The authors propose that introverts are less able to multitask and thus are poorer at nonverbal decoding, but only when it is a secondary task. Prior research has uniformly extracted the nonverbal decoding from its multitasking context and, consequently, never tested this hypothesis. In Studies 1–3, introverts exhibited a nonverbal decoding deficit, relative to extraverts, but only when decoding was a secondary rather than a primary task within a multitasking context. In Study 4, extraversion was found to correlate with central executive efficiency (r?=?.42) but not with storage capacity (r?=?.04). These results are discussed in terms of arousal theories of extraversion and the role of catecholamines (dopamine and norepinephrine) in prefrontal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)