Extraversion and neuroticism in orienting reflex dishabituation

The present study examined the effects of extraversion (E) and neuroticism (N) as individual difference dimensions and of stimulus intensity on electrodermal orienting response habituation, test response, and dishabituation. Subjects were 162 college students selected from a screening sample of 860 as representing extreme groups of high, medium, and low E crossing with high, medium, and low N. Subjects in all nine resulting groups were habituated to criterion on auditory stimuli of 60, 80, and 100 db. A novel (test) stimulus and a dishabituating standard stimulus followed criteron habituation at each intensity. Results indicated that response amplitude for initial, test, and dishabituation responses was a direct function and that habituation rate (trials-to-criterion) was an inverse function of stimulus intensity. Extraverts habituated more rapidly than introverts at high intensity and gave smaller test and dishabituation responses. Some results differed when regression coefficients defined habituation rate and when first stimulus intensities alone were examined. Correlations among initial, test, and dishabituation responses and between each of these and the two measures of habituation rate are also reported. Results were interpreted as partially supportive of Eysenck's theory.     

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.     

Extraversion and electrodermal activity: arousability and the inverted-U

The Eysenck hypothesis that extraverts are less aroused or more inhibited than introverts has been subjected to a number of tests in the psychophysiological literature. Research to date suggests the need to clearly differentiate between tests of overall group differences in arousal or inhibition and studies of the differential reactions of the two groups to arousal manipulations. Psychophysiological studies of overall arousal differences in our laboratories and elsewhere have yielded somewhat inconsistent results for SCL, nonspecific response frequency, trials-to-criterion habituation and initial response amplitude, though dishabituation results are consistent with the expectation of higher amplitudes in introverts. Far more consistent are findings testing the inverted-U hypothesis, which suggests that introverts reach a point of optimal arousal at lower levels of stimulus input than do extraverts and hence should show earlier asymptotes and decrements in arousal measures. Using stimulus intensity and caffeine to manipulate arousal, we have found supportive results for SCL and several phasic measures, including the initial, test, and dishabituation responses. Overall, findings suggest that the two personality groups differ more clearly in arousability than in overall arousal level and that this difference is most consistent when conditions induce a rapid breakdown of inhibition and increase in arousal. Further research is needed to better understand the conditional relationship of extraversion to arousability, and arousal-manipulation paradigms would appear to be a fruitful initial approach to carrying out the needed research.     

Exploring the mechanism of dishabituation

In this study we explored elicitation and habituation of the orienting reflex (OR) in the context of indifferent and significant stimuli, particularly aiming to clarify the mechanism driving dishabituation. An in-depth analysis of the mechanisms of electrodermal habituation and dishabituation was conducted, focusing on the role of state measures as determinants of the phasic response profile. Twenty-four young adult participants completed an auditory dishabituation task while electrodermal activity was recorded. Participants listened to a series of 10 innocuous tones of the same frequency (standards), followed by a deviant tone of a different frequency, and succeeded by 2-4 tones of the same frequency as the initial 10 stimuli. All stimuli had a random stimulus onset asynchrony of 5-7 s. Participants completed an indifferent condition in which there was no task in relation to the stimuli, and a significant condition where instruction was given to count the stimuli silently; order was counterbalanced between participants. As predicted, both skin conductance responses (SCRs) and skin conductance levels (SCLs) were larger for the significant than the indifferent condition. The initial phasic ORs were dependent on pre-stimulus arousal level, and there were significant decreases in both SCR and SCL over the first 10 standards in both conditions. Phasic response recovery was apparent to the deviant stimulus, and dishabituation to the following standard stimulus; both effects were enhanced in the significant condition. Sensitisation was apparent in SCL following the initial and deviant stimuli, but the extent of this was confounded with incomplete resolution of the preceding phasic OR in the significant condition. In the indifferent condition, dishabituation was independent of deviant-related sensitisation; this could not be tested in the significant condition. These findings suggest that dishabituation is not a process of sensitisation, but rather, a disruption of the habituation process.     

Dishabituation in Aplysia can involve either reversal of habituation or superimposed sensitization

Dishabituation has been thought to be due either to reversal of the process of habituation or to a second process equivalent to sensitization superimposed on habituation. One way to address this question is by testing whether dishabituation and sensitization can be dissociated. Previous studies using this approach in Aplysia have come to different conclusions about the nature of dishabituation, perhaps because those studies differed in many respects, including (1) whether they also observed transient behavioral inhibition, and (2) whether they used test stimuli that activated the LE siphon sensory neurons or as yet unidentified sensory neurons. To attempt to resolve the apparent contradictions between the previous studies, we have explored the importance of these two factors by performing a parametric study of dishabituation and sensitization of gill withdrawal in a simplified preparation that does not exhibit transient behavioral inhibition, using two different test stimuli that are known to activate the LE (Touch) or unidentified (Not Touch) sensory neurons. We find that dishabituation and sensitization in this preparation have similar time courses and generally similar functions of shock intensity. However, under one condition, with the Not Touch stimulus 2.5 min after the shock, dishabituation has a reverse effect of shock intensity. Additional analyses suggest that dishabituation with the Not Touch stimulus 2.5 min after the shock is due to reversal of habituation, whereas 12.5 min after the shock, dishabituation is due to superimposed sensitization. These results thus suggest that dishabituation may involve either process in the same preparation, and begin to define the conditions that favor one or the other.     

Electrodermal activity and extraversion: Caffeine,preparatory signal and stimulus intensity effects

The Eysenck hypothesis that introverts are more and extraverts less cortically aroused has been supported by the results of most electrodermal studies, though there is some inconsistency in the literature. Further tests of the hypothesis can be carried out using arousal-manipulation paradigms. Some studies have used caffeine or stimulus intensity to increase arousal, as was also the case in the present study. The latter, however, also introduced a preparatory signal, which may be expected under certain conditions, to reduce responses to the stimulus which follows it. Extraverts and introverts were randomly assigned to receive low, medium or high doses of caffeine or a placebo. Each S then heard two sets of tones with the tones in one set preceded by a preparatory signal. Results showed that the preparatory signal reduced phasic amplitudes only at the highest levels of stimulus intensity. Introverts had higher overall SCLs and response magnitudes. In addition, the preparatory signal had little effect on extraverts, but reversed dosage-related response patterns in introverts. Results were supportive of the basic Eysenck arousal hypothesis and also showed that the arousal difference leads to attentional variability between the two groups.     

Habituation and the human evoked potential

Habituation of human scalp-recorded cerebral evoked potentials was studied in response to auditory and visual repetitive stimuli of different intensities. Changes in magnitudes of evoked potentials with stimulus repetition were examined according to the parametric characteristics of habituation, generalization, and dishabituation. In addition, tests of the predictions of two theories of habituation were made regarding the degree and direction of intensity generalization of habituation. Both auditory and visual evoked potentials exhibited decrements in response magnitudes across the repetitive stimuli consistent with the parametric criteria of habituation. Early evoked potential peak components showed a pattern of intensity generalization of habituation consistent with the predictions of the dual-process theory of habituation. Intensity generalization of late evoked potential peak components occurred in a manner more consistent with the predictions of the stimulus comparator theory of habituation. These results provide further evidence that evoked potentials can be used as electrophysiological indexes of plasticity in humans.     

Cardiac orienting responses of 6- and 16-week-old infants

Since previous data suggested that the magnitude of orienting evidenced by cardiac deceleration increased over the first 16 weeks of life, 6- and 16-week-old infants were compared on various characteristics of orienting: habituation, dishabituation, and magnitude of deceleration to stimulus offset as well as to stimulus onset. Neither the change in stimulus following habituation trials nor the stimulus offset produced a large enough response to confidently evaluate age differences suggested by the data. Stimulus onset elicited a pronounced deceleration which for the two age groups was of equivalent magnitude on initial trials and declined similarly with stimulus repetition. It was suggested that similarity of the two age groups on these parameters was due to control of state within a narrow alert range, and that, in general, younger infants are less likely than older infants to show orienting when conditions for orienting are marginal.     

Auditory habituation in the fetus and neonate: an fMEG study

Habituation – the most basic form of learning – is used to evaluate central nervous system (CNS) maturation and to detect abnormalities in fetal brain development. In the current study, habituation, stimulus specificity and dishabituation of auditory evoked responses were measured in fetuses and newborns using fetal magnetoencephalography (fMEG). An auditory habituation paradigm consisting of 100 trains of five 500 Hz tones, one 750 Hz tone (dishabituator) and two more 500 Hz tones, respectively, were presented to 41 fetuses (gestational age 30–39 weeks) and 22 newborns or babies (age 6–89 days). A response decrement between the first and fifth tones (habituation), an increment between the fifth tone and the dishabituator (stimulus specificity) and an increment between the fifth (last tone before the dishabituator) and seventh tones (first tone after the dishabituator) (dishabituation) were expected. Fetuses showed weak responses to the first tone. However, a significant response decrement between the second and fifth tones (habituation) and a significant increment between the fifth tone and the dishabituator (stimulus specificity) were found. No significant difference was found for dishabituation nor was a developmental trend found at the group level. From the neonatal data, significant values for stimulus specificity were found. Sensory fatigue or adaptation was ruled out as a reason for the response decrement due to the strong reactions to the dishabituator. Taken together, the current study used fMEG to directly show fetal habituation and provides evidence of fetal learning in the last trimester of pregnancy.     

Dishabituation and spontaneous recovery of the electrodermal orienting response: Effects of extraversion,impulsivity, sociability,and caffeine

The relationship between extraversion and psychophysiological indices of arousal is not yet fully understood. The present study attempted to further clarify this relationship by using caffeine to systematically manipulate arousal. Subjects pretested on the Eysenck Personality Inventory were given caffeine or a placebo, then underwent habituation, dishabituation, and spontaneous recovery of the electrodermal OR. Separate analyses examined the main and interactive effects of extraversion, impulsivity, and sociability with caffeine. Several tonic and phasic measures showed group reversal effects, with introverts having higher tonic levels and larger phasic responses under placebo conditions and extraverts having larger phasic responses and higher tonic levels under caffeine. Although both tonic and phasic responses were differentially affected, the group reversal effects occurred at different points in time on tonic than they did on phasic measures relative to the theoretical buildup of inhibition. The findings for impulsivity were quite consistent with those for extraversion, and both sets of results were generally supportive of the Eysenck hypothesis.     

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.     

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.     

Reliability of electrodermal habituation measures under two conditions of stimulus intensity

The present study investigated test-retest reliability of habituation of the evoked skin conductance response. Subjects received 20 presentations of a 1000-Hz, 3-sec tone at the same time of day on two separate occasions, separated by an interval of 97–160 days. Thirteen subjects received stimuli of 90 dB, while for 24 subjects, stimulus intensity was 70 dB. Interstimulus interval was 21 sec for both groups. Both absolute rate of habituation and trials to criterion displayed moderate reliability, and the relationships between habituation measures and other aspects of electrodermal activity were in agreement with previous findings.     

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.     

Effects of noise on sensitivity of introverts and extraverts to signals in a vigilance task

Forty Ss, previously classified as introverts or extraverts on the basis of scores on the Eysenck Personality Inventory, performed a visual vigilance task while being stimulated with noise at an intensity level of either 65 or 85 dB. Introverts given noise of 65 dB intensity showed an improvement in detection rate across trials, whereas introverts given noise of 85 dB intensity showed a decline in detection rate. Extraverts responded to noise of 65 dB intensity with a slight decrease in detection rate, but showed an improvement in detection over trials when noise of 85 dB intensity was given. When noise of the lower intensity was given, introverts showed greater sensitivity to signals than extraverts. When noise of the higher intensity was given, introverts and extraverts were equal in sensitivity. The results are discussed in terms of a hypothesized relationship between stimulation and arousal, with E-I as a moderator variable.     

Habituation and dishabituation during object play in kennel-housed dogs

Domestic dogs are reported to show intense but transient neophilia towards novel objects. Here, we examine habituation and dishabituation to manipulable objects by kennel-housed dogs. Labrador retrievers (N?=?16) were repeatedly presented with one toy for successive 30-s periods until interaction ceased. At this point (habituation), a different toy was presented that contrasted with the first in both colour and odour (since the dog’s saliva would have accumulated on the first), colour alone, or odour alone. No effect of the type of contrast was detected in the number of presentations to habituation, the difference in duration of interaction between the first presentation of the first toy and the presentation of the second toy (recovery), or the duration of interaction with the second toy (dishabituation). Varying the time interval between successive presentations of the first toy up to habituation between 10?s and 10?min had no effect on the number of presentations to habituation, nor did it alter the extent of dishabituation. Varying the delay from habituation to presentation of the second toy, between 10?s and 15?min, affected neither the recovery nor the dishabituation. Overall, the study indicates that loss of interest in the object during object-orientated play in this species is due to habituation to the overall stimulus properties of the toy rather than to any single sensory modality and is also atypical in its insensitivity to the interval between presentations.     

Habituation, response to novelty, and dishabituation in human infants: tests of a dual-process theory of visual attention

Two experiments were conducted to test a dual-process theory of infants' performance on visual habituation-dishabituation tasks. The findings demonstrate that (a) infant habituation functions are often nonmonotonic, with fixation increasing before the eventual response waning; (b) this initial increment in responding is related to stimulus "complexity"; (c) response to novelty is enhanced by increasing the "complexity" of the novelty-test stimulus; and (d) dishabituation, followed by decay, occurs for familiarized patterns when retested after the introduction of a "complex" stimulus, but not after introduction of a "simple" stimulus. Following P. Groves and R. Thompson (1970, Psychological Review, 77, 419-450) we propose that infant visual attention to repeated presentations of a stimulus involves two processes, habituation and sensitization.     

Discrimination by newborns of the intensity, frequency and temporal characteristics of auditory stimuli

The ability of 3- to 5-day-old neonates to discriminate between auditory stimuli, in terms of each of the dimensions of intensity, pitch and time, was studied using heart-rate responses in a habituation paradigm. For each of the dimensions a survey of the literature failed to provide results which could be used as the basis for later work involving auditory patterns. Further analysis of an earlier experiment (Stratton, 1970 a) involving stimuli at 80, 85 and 90 db showed that louder stimuli evoked larger initial responses and more rapid habituation. From the same experiment it was found that a change of pitch produced dishabituation as early as the 10th trial. There are reasonable grounds for attributing the increased response to the frequency characteristics rather than a change in the perceived intensity of the stimuli. Previous experiments suggested that fixed inter-stimulus intervals tended to produce anticipatory heart-rate changes and modify the magnitude and latency of the response. Two experiments designed specifically to examine temporal phenomena revealed time-linked behaviour. In both experiments acceleratory responses occurred at the first stimulus omission of a fixed-interval series. Not all of the subjects showed this effect, and in both experiments, only the subjects who failed to respond to the first stimulus presentation responded to stimulus omission. The findings are discussed in relation to general issues of neonatal psychophysiology, and it is concluded that neonates can discriminate in each of the auditory dimensions, but that preliminary work involving patterns should concentrate on varying pitch and intensity.     

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.     

Individual differences in speed of retrieval from semantic memory

In the first of two experiments, the stimulus items consisted of category names followed by a single letter (e.g., fruit-P). The subjects (half introverted, half extraverted) were required to respond as quickly as possible with a member of the specified category starting with the letter. Extraverts responded significantly faster than introverts, and more so when the most likely response was of low frequency than when it was of high frequency. In the second experiment, subjects were assigned to one of four groups representing the four combinations of high and low Extraversion and high and low General Activation. The speed-of-recall task from the first experiment was used on some trials; on the remaining trials, a speed-of-recognition task was used. Extraverts had greater response speed than introverts for recall, but not for recognition. That finding, plus interactions between Extraversion and General Activation, suggested an interpretation of the results in terms of the Yerkes-Dodson Law.