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Habituation and dishabituation of the electrodermal orienting reflex in relation to extraversion and neuroticism
JOURNAL
OF RESEARCH
Habituation
IN PERSONALITY
10,
437-445 (1976)
and Dishabituation of the Electrodermal Orienting Reflex in Relation to Extraversion and Neuroticism
MICHAEL J. WIGGLESWORTH AND BARRY D. SMITH University
of Maryland
Orienting reflex (OR) habituationand dishabituationmay be influencedby individual difference variables, including Eysenck’s Extraversion (E) and Neuroticism (N) dimensions. Ninety subjects formed nine groupsbasedon the crossover of high, medium, and low E and N. Each subject received, at each of two auditory stimulus intensities, two blocks of tone presentations. The last standard stimulus trial was followed by a novel stimulus and four repetitions of the standard stimulus. Using square root SCR, extraverts showed smaller initial response amplitudes than introverts at the low intensity of stimulation, while the reverse was true at high intensity. E and N were unrelated to SCR habituation rate. However, extraverts showed no dishabituation, while introverts did dishabituate.
The hypotheses of Sokolov (1960, 1963) relating to stimulus intensity effects (Davis & Wagner, 1969; Groves & Thompson, 1970) and to the return of responding to the standard stimulus (SS) following the interposition of a novel stimulus, i.e., dishabituation (O’Gorman, 1973), have not received consistent support. Studies of dishabituation have yielded particularly mixed results. Some investigators report clear evidence for dishabituation (Furedy & Scull, 1971; Zimny & Schwabe, 1966), others report only a response to the novel or test stimulus (TS) and not to the dishabituation stimulus (Yaremko, Blair & Leckhart, 1970), and still others report no significant responding to either stimulus (Fried, Korn & Welch, 1966; Fried, Welch, & Friedman, 1%6). Moreover, while any change in a stimulus should produce an OR, decreases in intensity of the test stimulus have done so in some studies (Bernstein, 1968; 1%9), but not in others (James & Hughes, 1959; O’Gorman, Mangan & Gowen, 1970; Edwards, Note 1). Given the diverse results in this literature, it is particularly relevant that some reviewers and theorists have noted the probable importance of individual difference variables in habituation and dishabituation The authors thank Dan Church for his aid in running subjects. Computer time was made available by the Computer Science Center at the University of Maryland. Requests for reprints should be made to Barry D. Smith, Department of Psychology, University of Maryland, College Park, MD 20742. 437 Copyright @ 1976 by Academic Press, Inc. All rights of reproduction in any form reserved.
438
WIGGLESWORTH
AND SMITH
phenomena (O’Gorman, 1973; Groves & Thompson, 1970). Since these two phenomena are thought to involve the interplay of excitatory and inhibitory processes (Sokolov, 1963; Groves & Thompson, 1970), it may be that individual difference dimensions postulated to reflect differences in excitation and inhibition can help to account for dishabituation results. One theoretical model proposes two such individual difference dimensions, extraversion and neuroticism, based specifically on excitatory and inhibitory processes (Eysenck, 1967). Some investigators have previously applied the Eysenck model to habituation and related phenomena with somewhat mixed results. Relevant investigations have selected subjects on the basis of the Eysenck measures of neuroticism (N) and extraversion (E) and have involved repeated presentations of either mild tones (Mangan & O’Gorman, 1%9; Coles, Gale, & Kline, 1971) or consonant trigrams (Sadler, Mefferd, & Houck, 1971). The amplitude of the phasic electrodermal response to the initial stimulus has been found to relate to both extraversion (Mangan & O’Gorman, 1969) and neuroticism (Mangan & O’Gorman, 1969; Orlebeke, 1973), though some other studies are not supportive of these findings (Coles et al., 1971; Sadler et al., 1971). Habituation rate has also been found to relate to both neuroticism (Coles et al., 1971) and extraversion (Mangan & O’Gorman, 1969). Another investigation, using a median split to establish high and low N and E groups, attributed to chance a single significant F ratio relating N and E to habituation (Koriat, Averill, & Malmstrom, 1973). The present study focused on the relationship of the Eysenck dimensions to dishabituation, a process not studied in the work noted above and one which has yielded mixed results and been particularly problematic for Sokolov’s theory (O’Gorman, 1973). In addition, present work was concerned with the interactive effects of stimulus intensity and the Eysenck dimensions on both dishabituation and habituation processes. Finally, there was major concern with the selection of the personality groups employed. Specifically, an attempt was made to select very extreme groups from a large initial sample (over 600 subjects as compared with much smaller numbers in earlier work) and to examine all nine groups formed by a three-way breakdown (high, middle, low) on each of the two Eysenck dimensions. METHOD
Subjects The Eysenck Personality Inventory (Eysenck & Eysenck, 1968) Form A, was administered to 645 students in an introductory psychology course at the University of Maryland. The test yields scores on Extraversion (E) and Neuroticism(N), as well as Lie (L) scores as a validity check. From the total sample, 90 subjects were selected to form nine groups of five males and
EXTRAVERSION
AND
OR
DISHABITUATION
439
five females. The nine groups represented high, medium, and low N crossing with high, medium, and low E. High and low groups were defined by scores of at least one SD above or below the normative means on the respective scales, and medium groups by scores within .5 SD of the normative means. One criterion ultimately had to be eased slightly in order to fill all the cells. Specifically, the cutoff for low N groups was changed from a score of 6 on the N scale to 7. The subjects with the lowest L scores were used when there was a choice. It is worth noting for future research that even with 645 initial subjects it was not possible to obtain more than 10 for some extreme cells. The product-moment correlation between E and N for the total group of 645 subjects was -.04. The means for E (12.4) and N (11.8) were within one point of the normative means of 13.1 and 10.9, respectively (Eysenck & Eysenck, 1968).
Apparatus Skin resistance was recorded on a Grass Model 5 polygraph, using a Model S-P1 low level dc preamplifier. Zinc electrodes, 2.22 cm in diameter and set in a plastic cup, were employed, along with a zinc sulfate electrolyte. Current density was 10.12 PA/cm*. Tones of 0.5~set duration were recorded and presented with a Sony tape deck and amplifier, splicing leader tape between tones to avoid print-through. Auditory stimuli were delivered through matched, calibrated earphones in a sound attenuated chamber.
Procedure Upon entering the laboratory, the subject completed a four-item state anxiety questionnaire, then was seated in a comfortable chair with a footstool in the sound chamber. Instructions told the subject that he or she would hear a series of tones through the earphones, that a physiological response would be recorded through electrodes but no shocks would be administered, and that he or she should simply attend to the tones and avoid movement ofthe left arm. While instructions were being given, the skin surface was cleaned with alcohol, and the electrodes were attached to the left palm and the back of the left wrist, using plastic clamps. The experimenter then left the chamber, and a 6-min prestimulation period preceded the first stimulus. Following the prestimulation period, each subject received: (a) 20 SS tones of 1000 HZ, with interstimulus interval (ISI) randomly varied between 15 and 25 set; (b) an 80-set nonstimulation period; (c) 10 additional tones with the same IS1 range. Steps (b) and (c) allowed for spontaneous recovery and rehabituation of the response to provide more stable habituation: (d) a 500 Hz, 0.5-set TS followed by four additional SSs, providing a basis for the examination of the test response and dishabituation. The above series was presented twice to each subject, once at 80 db, once at 100 db (re BOO2 dynes/cm’). A 2 min interblock interval with no stimulation occurred between intensities. The sequence of presentation of intensities was counterbalanced, such that an equal number of subjects in each EPI group received each sequence. At the end of the session the subject again completed the anxiety questionnaire and a screening questionnaire concerning alcohol and drug usage, hearing loss, and brain damage. Eight subjects were dropped on the basis of the latter questionnaire.
RESULTS
The basic analysis of variance design was a three-between, twowithin-subjects model. Levels of E(3), levels of N (3), and sequence of intensity presentation (Hi-Lo, Lo-Hi) were between-subjects. Intensity (80 and 100 db) was within-subjects, as was trial, in those analyses involving two trials at each intensity.
440
WIGGLESWORTH
AND SMITH
Response Measures
Any decrease in resistance beginning between 1 and 4 set after tone onset was considered a response to the tone. The square root SCR values analyzed were determined as the square root of the difference in micromhos between the reciprocals of pre- and post-stimulus resistance values. The square root transformation was utilized to normalize the data. Habituation of tone-specific responses was defined as occurring with two successive responses of less than 1000 ohms. Initial Amplitude and Habituation Rate
As expected, there was a significant effect of intensity, F (1, 72) = 45.10, p < .OOl, on the amplitude of responses to Trial 1, the 100 db tone producing larger responses (a mean of 1.26) than the 80 db tone (.85). The sequence effect, F (1, 72) = 6.09, p < .025, and the intensity x sequence interaction, F (1, 72) = 15.36, p < .OOl, were also significant. Means for the high-low and low-high sequences were, respectively, 0.93 and 1.78. The interaction was due to the fact that means for the high intensity were nearly identical under the two sequences (1.25 and 1.26), while the low intensity mean was smaller in the high-low sequence (0.61) than in the low-high sequence (1.09). In addition, the extraversion x intensity interaction (Fig. 1) was significant, F (2, 72) = 4.50,~ < .025. Extraverts showed the smallest initial response to the 80 db tone, introverts the largest. However, at 100 db, the order of groups was reversed. The E and N variables were unrelated to habituation rate. The effect of intensity was significant, subjects requiring longer to habituate to the 100
Intensity
(db)
FIG. 1. Initial response amplitude as a function of extraversion and stimulus intensity.
EXTRAVERSION
AND OR DISHABITUATION
441
db tone (14.4 mean trials) than to the 80 db tone (6.6 trials). The sequence effect and the intensity x sequence interaction were also significant. To allow for the possibility that responses may start again after the habituation criterion has been reached, the total responses made by each subject were entered into a separate analysis. The pattern of results was similar to that on the trials to habituation measure, with significant effects of intensity, F (1, 72) = 193.83, p < .OOl, and the sequence x intensity interaction, F (1, 72) = 27.84, p < .OOl, but no N or E effects. Test Responses and Dishabituation Analyses of the test response involved the last SS (Trial 30) and the TS (Trial 31). As was expected, there was a larger response to the TS than to the preceding SS, leading to a significant trial effect, F (1, 72) = 170.04, p < .OOl . The mean response amplitude for the SS was .21, and that for the TS was .73. The effect of intensity, F (1, 72) = 41.03,~ < .OOl, indicated that the increase in response amplitude across both trials was greater at 100 db than at 80 db. The analyses of dishabituation involved the last SS (Trial 30) and the repetition of the SS (Trial 32) following the interposition of the TS. The intensity effect was significant, F (1, 72) = 36.24, p < .OOl, as in other .analyses. The interaction of extraversion with trial, F (2, 72) = 7.19, p < .005 (Fig. 2) resulted from the fact that introverts (Low E subjects) showed the greatest degree of dishabituation and extraverts the least dishabituation. In fact, the latter group showed no dishabituation at all, as their response on Trial 32 was slightly smaller than that on Trial 30. 0.42 0.38 a34 5 ;
-
0.30 -
‘0 a” 0.26 u s g 0.220.18
t
of
T 30
T 32 Trials
FIG.
2. Dishabituation
response amplitude as a function of extraversion.
442
WIGGLESWORTH
Nonspecific
Responses
and Spontaneous
AND
SMITH
Recovery
Total nonspecific responses during combined stimulation and 80-set interintensity nonstimulation periods were determined for each subject. There were no reliable effects. The last trial preceding the nonstimulation period and the first trial following that period were entered into an analysis of the spontaneous recovery of the OR. A significant effect of trial, F (1, 72) = 37.78, p < .OOl, indicated that there was a significant amount of spontaneous recovery of the habituated response. Means for Trials 20 and 21 were .24 and .51, respectively. The only other significant effect was that of intensity. Anxiety
Questionnaire
Separate anxiety questionnaire scores were determined pre- and postexperimentally for each subject. Analysis of variance yielded a significant effect of occasion (pre vs. post), F (1, 81) = 19.05, p < .OOl, reflecting a decrease in anxiety over the experimental session. The main effect of neuroticism, F (2, 81) = 4.60, p < .025, was due to higher anxiety in high than medium or low neurotic subjects. A significant interaction of extraversion with neuroticism was also seen, F (4, 81) = 2.60,~ < .05. Both extraverts and ambiverts (middle group) showed increasing anxiety as neuroticism increased. However, introverts showed a pattern of lowest anxiety in the middle-neuroticism group, DISCUSSION Present results support, first, the effectiveness of the principal experimental manipulations utilized in the study. One indication is the consistent presence of an intensity effect, indicating larger phasic response magnitudes to high than low intensity stimulation. In addition, habituation rate was inversely related to intensity, as in previous research (Dickinson & Smith, 1973). Further, the interaction of sequence with intensity showed that responses to low intensity stimulation were decreased by prior exposure to high intensity, while high intensity responses were essentially unaffected by sequence. Finally, results indicated that there was both a response to the TS and a dishabituation response to the following SS, thus making possible group comparisons concerned with dishabituation. Present findings concerning dishabituation were supportive of some previous literature reporting either a response to the TS (Furedy, 1968; Gabriel & Ball, 1970; Grim & White, 1965; Yaremko et al., 1970) or a dishabituation response to the following SS (Furedy & Scull, 1971) or both (McCubbin 8z Katkin, 1971; Zimny & Schwabe, 1%6). The relationship of dishabituation to extraversion and neuroticism was the primary focus of the present study, which also examined other
EXTRAVERSION
AND
OR
DISHABITUATION
443
psychophysiological variables. The assessment of the independent effects of the two personality dimensions showed that neuroticism was unrelated to the psychophysiological variables, while extraversion did relate significantly to some aspects of responding. First, the E dimension interacted with stimulus intensity to affect initial response amplitude, such that extraverts were more responsive than introverts under high intensity stimulation, while the reverse was true at a lower intensity. The finding is consistent with earlier work on the relative salivary responsivity of introverts and extraverts to weak and strong stimulation (Eysenck & Eysenck, 1967). Specifically, it was found that introverts showed larger responses than extraverts to a relatively mild stimulus of lemon juice on the tongue, but a relatively smaller response increment when a stronger stimulus (swallowing lemon juice) was presented. Previous electrodermal studies of initial response have not systematically varied stimulus intensity, and results have been mixed, with extraverts more responsive in one study (Mangan & O’Gorman, 1969) and introverts more responsive in another (Orlebeke, 1973). The reversal in relative response amplitudes of the two personality groups at lower and higher stimulus intensities can readily be interpreted in terms of the close similarity between the extraversion-introversion dimension (Eysenck, 1967) and the Russian dimension of strength of the nervous system (Teplov, 1964; Nebylitsyn, 1966). Essentially, introversion corresponds to the weak nervous system, extraversion to the strong nervous system (Eysenck, 1966; Gray, 1%7). The weak nervous system is more sensitive to stimulation, giving larger responses at low stimulus intensities and showing transmarginal inhibition and consequent response decrement at high intensities (Gray, 1964, 1967). Introverts in the present study displayed essentially this pattern of initial responses relative to extraverts. While the more highly aroused introvert may reduce initial responding under high intensity stimulation, Eysenck (1967) hypothesizes that with repeated stimulation it is the extravert who accumulates greater amounts of inhibition and hence should show reduced responding. Support for this hypothesis is seen in the present data indicating that introverts showed clear dishabituation following the interposition of a novel (test) stimulus, while extraverts did not. Since the degree of novelty needed to disinhibit is directly related to the amount of inhibition present (Sokolov, 1963), it can be hypothesized that the test stimulus was not sufficiently novel to produce dishabituation in the more (physiologically) inhibited extraverts. If this theoretical account is accurate, it may be possible in further research to demonstrate that a more novel (i.e., more discrepant) stimulus, possibly one in a different modality from the habituation stimulus, will produce dishabituation in the extraverted group.
444
WIGGLESWORTH
AND
SMITH
Overall, present results support the observation that individual differences may affect the dishabituation process (O’Gorman, 1973; Groves & Thompson, 1970), as well as the amplitude of initial responses. In addition, support is provided for specific aspects of Eysenck’s (1967) theory. Finally, it was found that the relationship between extraversion and initial response amplitude is a function of stimulus intensity, suggesting the need for further examination of the role of intensity in mediating the influence of individual difference variables on psychophysiological functioning. REFERENCES Bernstein, A. S. The orienting response and the direction of stimulus change. Psychonomic Science, 1968, 12, 127-128. Bernstein, A. S. To what does the orienting response respond. Psychophysiology, 1969, 6, 338-350.
Coles, M. G. H., Gale, A., & Kline, P. Personality and habituation of the orienting reaction: Tonic and response measures of electrodermal activity. Psychophysiology, 1971, 8, 54-63.
M., & Wagner, A. R. Habituation of startle response under incremental sequence of stimulus intensities. Journal of Comparative and Physiological Psychology, 1969, 67,
Davis,
486-492.
Dickinson, J. R., & Smith, B. D. Nonspecific activity and habituation of tonic and phasic skin conductance in somatic complainers and controls as a function of auditory stimulus intensity. Journal of Abnormal Psychology, 1973, 82, 404-413. Eysenck, H. J. Conditioning, introversion-extraversion and the strength of the nervous system. Procedures of the 18th International Congress of Experimental Psychology, Moscow. Ninth Symposium, 1966, 33-44. Eysenck, H. J. The biological basis of personality. Springfield, Illinois: Thomas, 1967. Eysenck, H. J., & Eysenck, S. B. G. Manual of the Eysenck Personality Inventory. San Diego: Educational and Industrial Testing Service, 1968. Eysenck, S. B. G. & Eysenck, H. J. Salivary response to lemon juice as a measure of introversion. Perceptual and Motor Skills, 1967, 24, 1047-1053. Fried, R., Kom, S., & Welch, L. Effect of change in sequential visual stimuli on GSR adaptation. Journal of Experimental Psychology, 1966, 72, 325-327. Fried, R., Welch, L., & Friedman, M. Stimulus novelty and intraseries primacy in GSR adaptation. Perception and Psychophysics, 1966, 1, 345-346. Furedy, J. J. Novelty and the measurement of the GSR. Journal of Experimental Psychology, 1968, 76, 501-503. Furedy, J. J., & Scull, J. Orienting-reaction theory and an increase of the human GSR following stimulus change which is unpredictable but not contrary to prediction. Journal of Experimental Psychology, 1971, 88, 292-294. Gabriel, M., & Ball, T. S. Plethysmographic and GSR response to single versus doublestimultaneous novel tactile stimuli. Journal of Experimental Psychology, 1970, 85, 368-373.
Gray, J. A. Pavlov’s typology, New York: Macmillan, 1964. Gray, J. A. Strength of the nervous system, introversion-extraversion, conditionability and arousal. Behavior Research and Therapy, 1967, 5, 151-170. Grim, P. F., & White, J. H. Effects of stimulus change on GSR and reaction time. Journal of Experimental Psychology, 1965, 69, 276-28 1. Groves, P. M., & Thompson, R. F. Habituation: A dual-process theory. Psychological Review, 1970, 77, 419-450.
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AND OR DISHABITUATION
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James, J. P., & Hughes, G. R. Habituation of the orienting response as a function of individual differences in anxiety and autonomic lability. Journal ofAbnormal Psychology, 1%9, 74, 54-60. Koriat, A., Averill, J. R., & Malmstrom, E. J. Individual differences in habituation: Some methodological and conceptual issues. Journal of Experimental Research in Personality, 1973,7,88-101. Mangan, G. L., & O’Gorman, J. G. Initial amplitude and rate of habituation of orienting reaction in relation to extraversion and neuroticism. Journal of Experimental Research in Personality, 1969, 3, 275-282. McCubbin, R. J., & Katkin, E. S. Magnitude of the orienting response as a function of extent and quality of stimulus change. Journal ofExperimental Psychology, 1971, 88, 182-188. Nebylitsyn, V. B. Fundamental properties of the human nervous system. Moscow: Akad. Pedagog. Nauk RSFSR, 1966. O’Gorman, J. G. Change in stimulus conditions and the orienting response. Psychophysiology, 1973, 10, 465-470. O’Gorman, J. G., Mangan, G. L., and Gowen, J. Selective habituation of the galvanic skin response component of the orientation reaction to an auditory stimulus. Psychophysiology, 1970, 6, 716-721. Orlebeke, J. F. Electrodermal, vasomotor and heart rate correlates of extraversion and neuroticism. Psychophysiology, 1973, 10, 211. Sadler, T. G., Mefferd, R. B. Jr., and Houck, R. L. The interaction of extraversion and neuroticism in orienting response habituation. Psychophysiology, 1971, 8, 312-318. Sokolov, E. N. Neuronal models and the orienting reflex. In M. A. Brazier (Ed.), The central nervous system and behavior. New York: Josiah Macy, Jr. Foundation, 1960. Pp. 187-276. Sokolov, D. N. Perception and the condition reflex. Oxford: Pergamon Press, 1963. Teplov, B. M. Problems in the study of general types of higher nervous activity in man and animals. In J. A. Gray (Ed.), Pavlov’s typology. New York: Macmillan, 1964. Pp. 3-153. Yaremko, R. M., Blair, M. W., & Leckhart, B. T. The orienting reflex to changes in a conceptual stimulus dimension. Psychonomic Science, 1970, 21, 115-l 16. Zimny, G. H. & Schwabe, L. W. Stimulus change and habituation of the orienting response. Psychophysiology,
1966, 2, 103-l
15.
REFERENCE
NOTE
1. Edwards, D. C. Habituation of the galvanic skin response to simple stimuli. Paper presented at the meeting of the Society for Psychophysiological Research, Clayton, Missouri, October 1971.
OF RESEARCH
Habituation
IN PERSONALITY
10,
437-445 (1976)
and Dishabituation of the Electrodermal Orienting Reflex in Relation to Extraversion and Neuroticism
MICHAEL J. WIGGLESWORTH AND BARRY D. SMITH University
of Maryland
Orienting reflex (OR) habituationand dishabituationmay be influencedby individual difference variables, including Eysenck’s Extraversion (E) and Neuroticism (N) dimensions. Ninety subjects formed nine groupsbasedon the crossover of high, medium, and low E and N. Each subject received, at each of two auditory stimulus intensities, two blocks of tone presentations. The last standard stimulus trial was followed by a novel stimulus and four repetitions of the standard stimulus. Using square root SCR, extraverts showed smaller initial response amplitudes than introverts at the low intensity of stimulation, while the reverse was true at high intensity. E and N were unrelated to SCR habituation rate. However, extraverts showed no dishabituation, while introverts did dishabituate.
The hypotheses of Sokolov (1960, 1963) relating to stimulus intensity effects (Davis & Wagner, 1969; Groves & Thompson, 1970) and to the return of responding to the standard stimulus (SS) following the interposition of a novel stimulus, i.e., dishabituation (O’Gorman, 1973), have not received consistent support. Studies of dishabituation have yielded particularly mixed results. Some investigators report clear evidence for dishabituation (Furedy & Scull, 1971; Zimny & Schwabe, 1966), others report only a response to the novel or test stimulus (TS) and not to the dishabituation stimulus (Yaremko, Blair & Leckhart, 1970), and still others report no significant responding to either stimulus (Fried, Korn & Welch, 1966; Fried, Welch, & Friedman, 1%6). Moreover, while any change in a stimulus should produce an OR, decreases in intensity of the test stimulus have done so in some studies (Bernstein, 1968; 1%9), but not in others (James & Hughes, 1959; O’Gorman, Mangan & Gowen, 1970; Edwards, Note 1). Given the diverse results in this literature, it is particularly relevant that some reviewers and theorists have noted the probable importance of individual difference variables in habituation and dishabituation The authors thank Dan Church for his aid in running subjects. Computer time was made available by the Computer Science Center at the University of Maryland. Requests for reprints should be made to Barry D. Smith, Department of Psychology, University of Maryland, College Park, MD 20742. 437 Copyright @ 1976 by Academic Press, Inc. All rights of reproduction in any form reserved.
438
WIGGLESWORTH
AND SMITH
phenomena (O’Gorman, 1973; Groves & Thompson, 1970). Since these two phenomena are thought to involve the interplay of excitatory and inhibitory processes (Sokolov, 1963; Groves & Thompson, 1970), it may be that individual difference dimensions postulated to reflect differences in excitation and inhibition can help to account for dishabituation results. One theoretical model proposes two such individual difference dimensions, extraversion and neuroticism, based specifically on excitatory and inhibitory processes (Eysenck, 1967). Some investigators have previously applied the Eysenck model to habituation and related phenomena with somewhat mixed results. Relevant investigations have selected subjects on the basis of the Eysenck measures of neuroticism (N) and extraversion (E) and have involved repeated presentations of either mild tones (Mangan & O’Gorman, 1%9; Coles, Gale, & Kline, 1971) or consonant trigrams (Sadler, Mefferd, & Houck, 1971). The amplitude of the phasic electrodermal response to the initial stimulus has been found to relate to both extraversion (Mangan & O’Gorman, 1969) and neuroticism (Mangan & O’Gorman, 1969; Orlebeke, 1973), though some other studies are not supportive of these findings (Coles et al., 1971; Sadler et al., 1971). Habituation rate has also been found to relate to both neuroticism (Coles et al., 1971) and extraversion (Mangan & O’Gorman, 1969). Another investigation, using a median split to establish high and low N and E groups, attributed to chance a single significant F ratio relating N and E to habituation (Koriat, Averill, & Malmstrom, 1973). The present study focused on the relationship of the Eysenck dimensions to dishabituation, a process not studied in the work noted above and one which has yielded mixed results and been particularly problematic for Sokolov’s theory (O’Gorman, 1973). In addition, present work was concerned with the interactive effects of stimulus intensity and the Eysenck dimensions on both dishabituation and habituation processes. Finally, there was major concern with the selection of the personality groups employed. Specifically, an attempt was made to select very extreme groups from a large initial sample (over 600 subjects as compared with much smaller numbers in earlier work) and to examine all nine groups formed by a three-way breakdown (high, middle, low) on each of the two Eysenck dimensions. METHOD
Subjects The Eysenck Personality Inventory (Eysenck & Eysenck, 1968) Form A, was administered to 645 students in an introductory psychology course at the University of Maryland. The test yields scores on Extraversion (E) and Neuroticism(N), as well as Lie (L) scores as a validity check. From the total sample, 90 subjects were selected to form nine groups of five males and
EXTRAVERSION
AND
OR
DISHABITUATION
439
five females. The nine groups represented high, medium, and low N crossing with high, medium, and low E. High and low groups were defined by scores of at least one SD above or below the normative means on the respective scales, and medium groups by scores within .5 SD of the normative means. One criterion ultimately had to be eased slightly in order to fill all the cells. Specifically, the cutoff for low N groups was changed from a score of 6 on the N scale to 7. The subjects with the lowest L scores were used when there was a choice. It is worth noting for future research that even with 645 initial subjects it was not possible to obtain more than 10 for some extreme cells. The product-moment correlation between E and N for the total group of 645 subjects was -.04. The means for E (12.4) and N (11.8) were within one point of the normative means of 13.1 and 10.9, respectively (Eysenck & Eysenck, 1968).
Apparatus Skin resistance was recorded on a Grass Model 5 polygraph, using a Model S-P1 low level dc preamplifier. Zinc electrodes, 2.22 cm in diameter and set in a plastic cup, were employed, along with a zinc sulfate electrolyte. Current density was 10.12 PA/cm*. Tones of 0.5~set duration were recorded and presented with a Sony tape deck and amplifier, splicing leader tape between tones to avoid print-through. Auditory stimuli were delivered through matched, calibrated earphones in a sound attenuated chamber.
Procedure Upon entering the laboratory, the subject completed a four-item state anxiety questionnaire, then was seated in a comfortable chair with a footstool in the sound chamber. Instructions told the subject that he or she would hear a series of tones through the earphones, that a physiological response would be recorded through electrodes but no shocks would be administered, and that he or she should simply attend to the tones and avoid movement ofthe left arm. While instructions were being given, the skin surface was cleaned with alcohol, and the electrodes were attached to the left palm and the back of the left wrist, using plastic clamps. The experimenter then left the chamber, and a 6-min prestimulation period preceded the first stimulus. Following the prestimulation period, each subject received: (a) 20 SS tones of 1000 HZ, with interstimulus interval (ISI) randomly varied between 15 and 25 set; (b) an 80-set nonstimulation period; (c) 10 additional tones with the same IS1 range. Steps (b) and (c) allowed for spontaneous recovery and rehabituation of the response to provide more stable habituation: (d) a 500 Hz, 0.5-set TS followed by four additional SSs, providing a basis for the examination of the test response and dishabituation. The above series was presented twice to each subject, once at 80 db, once at 100 db (re BOO2 dynes/cm’). A 2 min interblock interval with no stimulation occurred between intensities. The sequence of presentation of intensities was counterbalanced, such that an equal number of subjects in each EPI group received each sequence. At the end of the session the subject again completed the anxiety questionnaire and a screening questionnaire concerning alcohol and drug usage, hearing loss, and brain damage. Eight subjects were dropped on the basis of the latter questionnaire.
RESULTS
The basic analysis of variance design was a three-between, twowithin-subjects model. Levels of E(3), levels of N (3), and sequence of intensity presentation (Hi-Lo, Lo-Hi) were between-subjects. Intensity (80 and 100 db) was within-subjects, as was trial, in those analyses involving two trials at each intensity.
440
WIGGLESWORTH
AND SMITH
Response Measures
Any decrease in resistance beginning between 1 and 4 set after tone onset was considered a response to the tone. The square root SCR values analyzed were determined as the square root of the difference in micromhos between the reciprocals of pre- and post-stimulus resistance values. The square root transformation was utilized to normalize the data. Habituation of tone-specific responses was defined as occurring with two successive responses of less than 1000 ohms. Initial Amplitude and Habituation Rate
As expected, there was a significant effect of intensity, F (1, 72) = 45.10, p < .OOl, on the amplitude of responses to Trial 1, the 100 db tone producing larger responses (a mean of 1.26) than the 80 db tone (.85). The sequence effect, F (1, 72) = 6.09, p < .025, and the intensity x sequence interaction, F (1, 72) = 15.36, p < .OOl, were also significant. Means for the high-low and low-high sequences were, respectively, 0.93 and 1.78. The interaction was due to the fact that means for the high intensity were nearly identical under the two sequences (1.25 and 1.26), while the low intensity mean was smaller in the high-low sequence (0.61) than in the low-high sequence (1.09). In addition, the extraversion x intensity interaction (Fig. 1) was significant, F (2, 72) = 4.50,~ < .025. Extraverts showed the smallest initial response to the 80 db tone, introverts the largest. However, at 100 db, the order of groups was reversed. The E and N variables were unrelated to habituation rate. The effect of intensity was significant, subjects requiring longer to habituate to the 100
Intensity
(db)
FIG. 1. Initial response amplitude as a function of extraversion and stimulus intensity.
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db tone (14.4 mean trials) than to the 80 db tone (6.6 trials). The sequence effect and the intensity x sequence interaction were also significant. To allow for the possibility that responses may start again after the habituation criterion has been reached, the total responses made by each subject were entered into a separate analysis. The pattern of results was similar to that on the trials to habituation measure, with significant effects of intensity, F (1, 72) = 193.83, p < .OOl, and the sequence x intensity interaction, F (1, 72) = 27.84, p < .OOl, but no N or E effects. Test Responses and Dishabituation Analyses of the test response involved the last SS (Trial 30) and the TS (Trial 31). As was expected, there was a larger response to the TS than to the preceding SS, leading to a significant trial effect, F (1, 72) = 170.04, p < .OOl . The mean response amplitude for the SS was .21, and that for the TS was .73. The effect of intensity, F (1, 72) = 41.03,~ < .OOl, indicated that the increase in response amplitude across both trials was greater at 100 db than at 80 db. The analyses of dishabituation involved the last SS (Trial 30) and the repetition of the SS (Trial 32) following the interposition of the TS. The intensity effect was significant, F (1, 72) = 36.24, p < .OOl, as in other .analyses. The interaction of extraversion with trial, F (2, 72) = 7.19, p < .005 (Fig. 2) resulted from the fact that introverts (Low E subjects) showed the greatest degree of dishabituation and extraverts the least dishabituation. In fact, the latter group showed no dishabituation at all, as their response on Trial 32 was slightly smaller than that on Trial 30. 0.42 0.38 a34 5 ;
-
0.30 -
‘0 a” 0.26 u s g 0.220.18
t
of
T 30
T 32 Trials
FIG.
2. Dishabituation
response amplitude as a function of extraversion.
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Nonspecific
Responses
and Spontaneous
AND
SMITH
Recovery
Total nonspecific responses during combined stimulation and 80-set interintensity nonstimulation periods were determined for each subject. There were no reliable effects. The last trial preceding the nonstimulation period and the first trial following that period were entered into an analysis of the spontaneous recovery of the OR. A significant effect of trial, F (1, 72) = 37.78, p < .OOl, indicated that there was a significant amount of spontaneous recovery of the habituated response. Means for Trials 20 and 21 were .24 and .51, respectively. The only other significant effect was that of intensity. Anxiety
Questionnaire
Separate anxiety questionnaire scores were determined pre- and postexperimentally for each subject. Analysis of variance yielded a significant effect of occasion (pre vs. post), F (1, 81) = 19.05, p < .OOl, reflecting a decrease in anxiety over the experimental session. The main effect of neuroticism, F (2, 81) = 4.60, p < .025, was due to higher anxiety in high than medium or low neurotic subjects. A significant interaction of extraversion with neuroticism was also seen, F (4, 81) = 2.60,~ < .05. Both extraverts and ambiverts (middle group) showed increasing anxiety as neuroticism increased. However, introverts showed a pattern of lowest anxiety in the middle-neuroticism group, DISCUSSION Present results support, first, the effectiveness of the principal experimental manipulations utilized in the study. One indication is the consistent presence of an intensity effect, indicating larger phasic response magnitudes to high than low intensity stimulation. In addition, habituation rate was inversely related to intensity, as in previous research (Dickinson & Smith, 1973). Further, the interaction of sequence with intensity showed that responses to low intensity stimulation were decreased by prior exposure to high intensity, while high intensity responses were essentially unaffected by sequence. Finally, results indicated that there was both a response to the TS and a dishabituation response to the following SS, thus making possible group comparisons concerned with dishabituation. Present findings concerning dishabituation were supportive of some previous literature reporting either a response to the TS (Furedy, 1968; Gabriel & Ball, 1970; Grim & White, 1965; Yaremko et al., 1970) or a dishabituation response to the following SS (Furedy & Scull, 1971) or both (McCubbin 8z Katkin, 1971; Zimny & Schwabe, 1%6). The relationship of dishabituation to extraversion and neuroticism was the primary focus of the present study, which also examined other
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psychophysiological variables. The assessment of the independent effects of the two personality dimensions showed that neuroticism was unrelated to the psychophysiological variables, while extraversion did relate significantly to some aspects of responding. First, the E dimension interacted with stimulus intensity to affect initial response amplitude, such that extraverts were more responsive than introverts under high intensity stimulation, while the reverse was true at a lower intensity. The finding is consistent with earlier work on the relative salivary responsivity of introverts and extraverts to weak and strong stimulation (Eysenck & Eysenck, 1967). Specifically, it was found that introverts showed larger responses than extraverts to a relatively mild stimulus of lemon juice on the tongue, but a relatively smaller response increment when a stronger stimulus (swallowing lemon juice) was presented. Previous electrodermal studies of initial response have not systematically varied stimulus intensity, and results have been mixed, with extraverts more responsive in one study (Mangan & O’Gorman, 1969) and introverts more responsive in another (Orlebeke, 1973). The reversal in relative response amplitudes of the two personality groups at lower and higher stimulus intensities can readily be interpreted in terms of the close similarity between the extraversion-introversion dimension (Eysenck, 1967) and the Russian dimension of strength of the nervous system (Teplov, 1964; Nebylitsyn, 1966). Essentially, introversion corresponds to the weak nervous system, extraversion to the strong nervous system (Eysenck, 1966; Gray, 1%7). The weak nervous system is more sensitive to stimulation, giving larger responses at low stimulus intensities and showing transmarginal inhibition and consequent response decrement at high intensities (Gray, 1964, 1967). Introverts in the present study displayed essentially this pattern of initial responses relative to extraverts. While the more highly aroused introvert may reduce initial responding under high intensity stimulation, Eysenck (1967) hypothesizes that with repeated stimulation it is the extravert who accumulates greater amounts of inhibition and hence should show reduced responding. Support for this hypothesis is seen in the present data indicating that introverts showed clear dishabituation following the interposition of a novel (test) stimulus, while extraverts did not. Since the degree of novelty needed to disinhibit is directly related to the amount of inhibition present (Sokolov, 1963), it can be hypothesized that the test stimulus was not sufficiently novel to produce dishabituation in the more (physiologically) inhibited extraverts. If this theoretical account is accurate, it may be possible in further research to demonstrate that a more novel (i.e., more discrepant) stimulus, possibly one in a different modality from the habituation stimulus, will produce dishabituation in the extraverted group.
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Overall, present results support the observation that individual differences may affect the dishabituation process (O’Gorman, 1973; Groves & Thompson, 1970), as well as the amplitude of initial responses. In addition, support is provided for specific aspects of Eysenck’s (1967) theory. Finally, it was found that the relationship between extraversion and initial response amplitude is a function of stimulus intensity, suggesting the need for further examination of the role of intensity in mediating the influence of individual difference variables on psychophysiological functioning. REFERENCES Bernstein, A. S. The orienting response and the direction of stimulus change. Psychonomic Science, 1968, 12, 127-128. Bernstein, A. S. To what does the orienting response respond. Psychophysiology, 1969, 6, 338-350.
Coles, M. G. H., Gale, A., & Kline, P. Personality and habituation of the orienting reaction: Tonic and response measures of electrodermal activity. Psychophysiology, 1971, 8, 54-63.
M., & Wagner, A. R. Habituation of startle response under incremental sequence of stimulus intensities. Journal of Comparative and Physiological Psychology, 1969, 67,
Davis,
486-492.
Dickinson, J. R., & Smith, B. D. Nonspecific activity and habituation of tonic and phasic skin conductance in somatic complainers and controls as a function of auditory stimulus intensity. Journal of Abnormal Psychology, 1973, 82, 404-413. Eysenck, H. J. Conditioning, introversion-extraversion and the strength of the nervous system. Procedures of the 18th International Congress of Experimental Psychology, Moscow. Ninth Symposium, 1966, 33-44. Eysenck, H. J. The biological basis of personality. Springfield, Illinois: Thomas, 1967. Eysenck, H. J., & Eysenck, S. B. G. Manual of the Eysenck Personality Inventory. San Diego: Educational and Industrial Testing Service, 1968. Eysenck, S. B. G. & Eysenck, H. J. Salivary response to lemon juice as a measure of introversion. Perceptual and Motor Skills, 1967, 24, 1047-1053. Fried, R., Kom, S., & Welch, L. Effect of change in sequential visual stimuli on GSR adaptation. Journal of Experimental Psychology, 1966, 72, 325-327. Fried, R., Welch, L., & Friedman, M. Stimulus novelty and intraseries primacy in GSR adaptation. Perception and Psychophysics, 1966, 1, 345-346. Furedy, J. J. Novelty and the measurement of the GSR. Journal of Experimental Psychology, 1968, 76, 501-503. Furedy, J. J., & Scull, J. Orienting-reaction theory and an increase of the human GSR following stimulus change which is unpredictable but not contrary to prediction. Journal of Experimental Psychology, 1971, 88, 292-294. Gabriel, M., & Ball, T. S. Plethysmographic and GSR response to single versus doublestimultaneous novel tactile stimuli. Journal of Experimental Psychology, 1970, 85, 368-373.
Gray, J. A. Pavlov’s typology, New York: Macmillan, 1964. Gray, J. A. Strength of the nervous system, introversion-extraversion, conditionability and arousal. Behavior Research and Therapy, 1967, 5, 151-170. Grim, P. F., & White, J. H. Effects of stimulus change on GSR and reaction time. Journal of Experimental Psychology, 1965, 69, 276-28 1. Groves, P. M., & Thompson, R. F. Habituation: A dual-process theory. Psychological Review, 1970, 77, 419-450.
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James, J. P., & Hughes, G. R. Habituation of the orienting response as a function of individual differences in anxiety and autonomic lability. Journal ofAbnormal Psychology, 1%9, 74, 54-60. Koriat, A., Averill, J. R., & Malmstrom, E. J. Individual differences in habituation: Some methodological and conceptual issues. Journal of Experimental Research in Personality, 1973,7,88-101. Mangan, G. L., & O’Gorman, J. G. Initial amplitude and rate of habituation of orienting reaction in relation to extraversion and neuroticism. Journal of Experimental Research in Personality, 1969, 3, 275-282. McCubbin, R. J., & Katkin, E. S. Magnitude of the orienting response as a function of extent and quality of stimulus change. Journal ofExperimental Psychology, 1971, 88, 182-188. Nebylitsyn, V. B. Fundamental properties of the human nervous system. Moscow: Akad. Pedagog. Nauk RSFSR, 1966. O’Gorman, J. G. Change in stimulus conditions and the orienting response. Psychophysiology, 1973, 10, 465-470. O’Gorman, J. G., Mangan, G. L., and Gowen, J. Selective habituation of the galvanic skin response component of the orientation reaction to an auditory stimulus. Psychophysiology, 1970, 6, 716-721. Orlebeke, J. F. Electrodermal, vasomotor and heart rate correlates of extraversion and neuroticism. Psychophysiology, 1973, 10, 211. Sadler, T. G., Mefferd, R. B. Jr., and Houck, R. L. The interaction of extraversion and neuroticism in orienting response habituation. Psychophysiology, 1971, 8, 312-318. Sokolov, E. N. Neuronal models and the orienting reflex. In M. A. Brazier (Ed.), The central nervous system and behavior. New York: Josiah Macy, Jr. Foundation, 1960. Pp. 187-276. Sokolov, D. N. Perception and the condition reflex. Oxford: Pergamon Press, 1963. Teplov, B. M. Problems in the study of general types of higher nervous activity in man and animals. In J. A. Gray (Ed.), Pavlov’s typology. New York: Macmillan, 1964. Pp. 3-153. Yaremko, R. M., Blair, M. W., & Leckhart, B. T. The orienting reflex to changes in a conceptual stimulus dimension. Psychonomic Science, 1970, 21, 115-l 16. Zimny, G. H. & Schwabe, L. W. Stimulus change and habituation of the orienting response. Psychophysiology,
1966, 2, 103-l
15.
REFERENCE
NOTE
1. Edwards, D. C. Habituation of the galvanic skin response to simple stimuli. Paper presented at the meeting of the Society for Psychophysiological Research, Clayton, Missouri, October 1971.