The Journal of General Psychology

ISSN: 0022-1309 (Print) 1940-0888 (Online) Journal homepage: http://www.tandfonline.com/loi/vgen20

Further Observations on the Incremental Stimulus Intensity Effect and Habituation of the Human Electrodermal Response J. G. O'gorman & R. D. Jamieson To cite this article: J. G. O'gorman & R. D. Jamieson (1978) Further Observations on the Incremental Stimulus Intensity Effect and Habituation of the Human Electrodermal Response, The Journal of General Psychology, 98:1, 145-154, DOI: 10.1080/00221309.1978.9920865 To link to this article: http://dx.doi.org/10.1080/00221309.1978.9920865

Published online: 06 Jul 2010.

Submit your article to this journal

Article views: 7

View related articles

Citing articles: 3 View citing articles

Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=vgen20 Download by: [University of Birmingham]

Date: 06 November 2015, At: 04:42

TIIFJ o u ~ n a lof Crncral Ps.vrho1og.v. 1978. 98, 145-154

FURTHER OBSERVATIONS ON T H E INCREMENTAL STIMULUS INTENSITY E F F E C T AND HABITUATION OF T H E HUMAN ELECTRODERMAL RESPONSE*' Departmrnt of Psyrhology, Uniurrsity of Nrw England, Australia

Downloaded by [University of Birmingham] at 04:42 06 November 2015

J . G . O'GORMANA N D R. D.

JAMIESON~

SUMMARY Two studies are reported which examined the relative effectiveness of an incremental series of stimulus intensities for reducing electrodermal responsiveness to a test stimulus. In the first study, employing five pairs of male undergraduates matched on electrodermal responsiveness, habituation to a 100 d b (re 20 pNlm2) noise burst was compared following two training procedures. In one. stimulation began at 64 d b and increased by 4 d b u p to 96 d b whenever two consecutive presentations of the stimulus failed to elicit a response. In the other, an equivalent number of presentations with a 100 d b noise burst were provided. While habituation occurred during both training conditions, subsequent habituation to a 100 d b test stimulus was more rapid following incremental training. In the second experiment, employing 40 female undergraduates, incremental and fixed conditions of training were compared for effectiveness using more moderate intensities of test stimulus: viz., 60 d b and 80 db. At these levels, the fixed training series was superior to the incremental in reducing responsiveness. The data extend previous findings on the incremental stimulus intensity effect with the human electrodermal response but suggest limiting conditions for its demonstration. A.

INTRODUCTION

In a previous study ( 7 ) , we observed that electrodermal responsiveness to a high intensity acoustic stimulus was reduced by preparatory response to a gradually increasing series of stimulus intensities. Repeated exposure to a 100

* Received in the Editorial Office. Provincetown. Masbachusetts, on December 30, 1976. Copyright, 1978, by The Journal Press, ' The work reported in this paper was supported by an award to the first author from the Australian Research Grants Committee. The second author is now at the Neuropsycholo~Unit. University of Aston in Birmingham, United Kingdom.

'

14 5

Downloaded by [University of Birmingham] at 04:42 06 November 2015

14 6

JOURNAL OF GENERAL PSYCHOLOGY

d b (re 20 pN/m2) noise burst resulted in no decrease in frequency of electrodermal responding over blocks of five trials, whereas response frequency to the noise was significantly reduced when stimulus presentation commenced at 80 d b and increased by 5 d b over blocks of five trials. The effect was similar to that first reported by Davis and Wagner (1) for long-term habituation of startle response in the rat and termed by Groves and Thompson (4)the incremental stimulus intensity effect (ISIE). The present studies were undertaken to explore further the ISIE and electrodermal habituation, Two questions were of concern. The first arose from a consideration of our earlier data which indicated that the difference in responding described as the ISIE was due to a failure of electrodermal habituation under the condition of constant stimulation. Had Ss receiving repeated exposure to the 100 d b noise burst shown a decrease in response over trials, their final level of responsiveness may not have differed significantly from that for Ss trained under the incremental condition who decreased over trials. In infrahuman studies of the ISIE, exposure to a fixed high intensity stimulus has produced a decrease in responsiveness. In the first experiment reported here an attempt was made to demonstrate the ISIE with the human electrodermal response under conditions which promoted habituation to the fixed high intensity stimulus. The second question investigated was the importance of the intensity of the test stimulus for the ISIE. In previous studies of the ISIE both human and infrahuman, the stimulus used has been intense. Most studies of habituation of human physiological responses however have employed low to moderate intensity stimuli, those which are considered to evoke attentional or orienting rather than defensive responses. As pointed out by Graham (2) and as noted in our previous report (7), the ISIE may be a feature of defensive and not orienting responses. As such the effect would not be a major parameter of habituation of all classes of physiological responses. The second experiment reported here was concerned with the comparison of incremental and constant conditions of training for reducing electrodermal responsiveness to stimuli within the low to moderate intensity range.

B.

EXPERIMENT1

The purpose of the first experiment was to compare the reduction in responsiveness to a high intensity acoustic stimulus produced with incremental and constant training series, but under conditions which ensured thatSs in both series habituated. The strategy adopted was to train allSs to a n habituation criterion of two consecutive response failures prior to testing. This

Downloaded by [University of Birmingham] at 04:42 06 November 2015

J. G . O’GORMAN A N D R. D. JAMIESON

14 7

ensured that Ss in both series showed a decrease in responsiveness during training and thus provided a more critical test of the efficacy of incremental and constant series for reducing responsiveness. In using a n individual S criterion, one difficulty is the considerable i n t e r s variance in electrodermal responding. Accordingly, Ss in the two series were matched for responsiveness prior to training. Matching was accomplished in terms of magnitude and latency of response to a moderate intensity stimulus. Latency was used in addition to magnitude in an attempt to equate Ss for speed of habituation. Matching in terms of actual speed of habituation to criterion would have resulted in considerable exposure to the acoustic stimulus prior to training. Hence latency, a correlate of speed of habituation (6) which minimized exposure, was employed. Once matched, pairs ofSs were allocated to incremental and constant series and were trained to the habituation criterion. In the incremental series this meant presenting sufficient stimuli at each intensity level to produce two consecutive response failures prior to increasing intensity. In the constant series, stimulus presentation continued until the habituation criterion was reached, and was then continued until each S had received the same number of stimulus presentations as his matched pair in the incremental series had received prior to testing. This was done to equate Ss in the two series for amount of training. 1.

Method

a. Subjects. Twenty male undergraduates volunteered for the study to complete a course requirement. One week prior to the training session each S was presented with a 1 sec burst of white noise a t 80 db. The method of stimulus presentation and response recording were the same as that used in training. Magnitude of the electrodermal response in micromhos and its latency in seconds to the noise burst were measured for each of the 20 Ss. The magnitude scores were then rank ordered and the latency scores split a t the median value for the sample (1.9 sec) to form short and long latency groups. Pairs of S s were formed by selecting successive pairs of ranks on response magnitude and each member of a pair was designated “short” or “long” in terms of latency. Pairs were then discarded if both members did not have the same designation on latency. This resulted in the elimination of three pairs of Ss. One member of each of the seven remaining pairs was randomly allocated to either the incremental or constant training condition and Ss were requested to return to the laboratory one week later. b . Apparatus. The equipment used for stimulus programming and re-

Downloaded by [University of Birmingham] at 04:42 06 November 2015

148

JOURNAL OF GENERAL PSYCHOLOGY

sponse recording was the same as that employed in the previous studies (7). Briefly, skin conductance response (SCR) and EKG were recorded with the use of appropriate electrodes and an E & M Physiograph. A tape-programmer presented the S , via headphones, a 1 sec white noise burst every 40 sec. Intensity of the stimulus was varied manually by the E . r . Procedure. Ss were studied individually in a quiet laboratory adjacent to that which housed the stimulus equipment and recording apparatus. The S was informed that loud noises would be presented through the headphones from time to time but that there was no response required of him. Ss were given the option of terminating the experiment at any time, but none did so. Stimulus presentation commenced once the electrodes were attached and a 10 min quiet period had elapsed. For each pair, the S allocated to the Incremental Series was studied first. Stimulus intensity in this series commenced a t 64 d b and was increased by 4 d b whenever two consecutive presentations of the stimulus failed to elicit the SCR. The series terminated when the habituation criterion was reached with presentation of the 100 db intensity. For the member of the pair allocated to the Constant Series, training involved repeated presentation of the 100 d b intensity. Once the habituation criterion of two consecutive response failures had been reached, additional presentations were provided, without interruption to the series, until the number of training trials with the 100 d b stimulus equalled the total number received by his matched partner under the Incremental Series. At this point in training further presentations of the 100 d b intensity were provided until the criterion of two consecutive response failures had again been reached. The experiment was terminated at this stage. 2.

Results

Two of the seven Ss trained under the incremental series did not reach the test intensity. For o n e s the habituation criterion was not reached following30 presentations a t 64 d b and training was discontinued. This S was found on postexperimental inquiry to have been attempting to time the interval between the noise bursts. The other S did not reach the criterion a t 80 d b within 30 presentations but no reason for this could be found on postexperimental inquiry. Thus complete data were available for only five pairs of Ss. Table 1 presents for each S pair a summary of the number of training and testing trials required. As column 2 indicates, considerable exposure to the stimulus was required to reach the test intensity under the incremental series but habituation was then quite rapid (column 3 ) . By comparison, Ss trained

14 9

Downloaded by [University of Birmingham] at 04:42 06 November 2015

J. G . O’GORMAN A N D R. D . JAMIESON

under the constant condition habituated only slowly to the 100 d b stimulus (column 4) and showed a return of response following criterion habituation. The habituation criterion was reached several times during the course of training for Ss in this series. When amount of training for the two series is equated, comparison of responsiveness to the test stimulus indicates a higher level for Ss in the Constant Series (columns 3 and 4), which constitutes a replication of the ISIE. Table 2 summarizes the data on magnitude of SCR and skin conductance level (SCL) and heart rate level during the experiment for Ss trained under the two conditions. Matched pair t tests indicated that from the first training trial to the test trial for both groups, there was a significant decrease in SCR, a significant increase in SCL, and no change in heart rate level HRL. Matched pair t tests between series indicated no significant differences a t the first training trial for SCL and HRL, but significantly greater SCR to the 100 d b noise. At the test trial there were no significant differences for SCL and HRL, but SCR was significantly lower on the test trial for Ss in the incremental series, an effect consistent with the trials-to-criterion index of habituation. 3.

Discussion

Consistent with the purpose of the study, habituation of the electrodermal response, whether indexed by adecrease in response amplitude from Trial 1 to the Test Trial or by a complete failure of response, occurred for Ss in both series. Thus differences between the series cannot be interpreted as the result of a selective failure of habituation. Under these conditions the superiority of the incremental series in reducing responsiveness to a high intensity stimulus is again demonstrated. The superiority is most dramatically indicated by the fact that for two S s trained under the incremental series no SCR was elicited on first presentation of the 100 d b noise burst. A stimulus which would be TABLE 1 NUMBER OF TRAINING TRIALSA N D NUMBER OF TRIALSTO HABITUATION TO TEST STIMULUS FOR EACH SUBIECT PAIR Subject pair

Number of training trials 68 51 85 52 57

Number of trials to habituation Incremental Constant condition condition Pretest Test 3

6 10 2 4

31 25 39 11

8

150

JOURNAL OF GENERAL PSYCHOLOGY TABLE 2 MEANMAGNITUDES OF PHYSIOLOGICAL RESPONSESON THE FIRSTAND TESTTRIALSUNDER THE T w o TRAININGCONDITIONS

Downloaded by [University of Birmingham] at 04:42 06 November 2015

Condition

SCR (umhos)

SCL (umhos)

HRL (bDm)

Trial 1 Incremental Constant

,0010 ,0015

,0130 ,0151

75

Test trial Incremental Constant

,0002 ,0006

,0182 ,0193

75 77

Note: SCR = Skin Conductance Response, SCL Rate Level.

=

78

Skin Conductance Level, HRL = Heart

expected to elicit a substantial change in conductance, and which in fact did on the first trial for Ss in the constant series, was thus rendered ineffective by exposure to the incremental series. Incremental training was however extensive and in one case could not be completed. The superiority of the incremental series in the present study was due to the fragile nature of habituation under the constant series. Studies of habituation of human physiological responses have not examined the effect of repeated presentation of high intensity stimuli, but for more moderate intensity stimuli, recovery of the habituated SCR with repeated presentation has been reported (5, 8). The recovery of response following criterion habituation with continued presentation of the 100 d b stimulus is similar to the overextinction effect reported in these previous studies. Whether habituation to the 100 d b stimulus following incremental training would be any more stable cannot be determined from the present data, though such stability would be expected in the light of the inverse correlation found between speed of initial habituation and recovery of the habituated response (5). The importance of recovery of response following habituation in the present context is that it results in the final level of responsiveness under constant training conditions being higher than that following incremental training. The results of the present study thus support our previous observations on the ISIE and electrodermal responding, though under individualized rather than fixed training conditions. There is however one discrepancy. SCL rose during both training series in the present study, whereas it decreased in the previous experiment under both conditions. Why this should be so is unclear, but it is further evidence against interpretation of the ISIE in terms of control of the general activating effects of stimulation (4).Both training series resulted

J . G . O’GORMAN AND R . D. JAMIESON

151

in similar increases in an index of general arousal and yet differences between series in terms of responsiveness to discrete stimulation were observed.

Downloaded by [University of Birmingham] at 04:42 06 November 2015

C.

EXPERIMENT 2

The purpose of this study was to compare incremental and constant series for reducing responsiveness to moderate intensity stimuli. Two test intensities, 60 d b and 80 db, considered representative of those commonly used in studies of habituation of human physiological responses, were employed. The incremental series consisted of 20 presentations, two each a t consecutive 2 d b increments up to the test intensity. These conditions of training were found most effective in an earlier study with a high intensity test stimulus (7). The constant series consisted of 20 presentations of the test intensity prior to the test trial. 1. Method

a . Subjects. Forty female undergraduates were randomly allocated to four groups of 10. TwoSs who failed to show an electrodermal response to any of the stimuli were replaced from the same S population. b. Apparatus. Stimulus programming was performed with the use of the equipment described earlier. The skin resistance response was recorded with the use of the same electrode system as in our previous studies but was amplified with a Grass Model 7P3 low gain dc preamplifier and written out on one channel of a Grass Polygraph. The event marker on the polygraph was activated by the stimulus programmer. The response was recorded as a change in resistance and transformed to conductance units. c . Procedure. Ss were tested individually in asound reduced laboratory. The ambient noise level of the headphone through which the stimulus was presented to the S varied from 38 to 42 d b as measured with a sound level meter. Prior to electrode attachment, Ss in all conditions were told that they would hear a series of noises from time to time through the headphones but that no response was required of them. The electrodes were then attached and stimulus presentation appropriate to the condition under test commenced after a 10 minute “quiet” period. Ss in the 60 d b constant and the 80 d b constant series received 2 2 one-sec noise bursts at 60 d b or 80 d b spaced at 40 sec intervals. Ss in the 60 d b incremental series received 2 2 one-sec noise bursts which began a t 40 d b and increased by 2 d b every two trials up to 60 db. For Ss in the 80 d b incremental

152

JOURNAL OF GENERAL PSYCHOLOGY

series the procedure was similar except that the noise burst commenced at 60 d b and increased in 2 d b steps to 80 db.

Downloaded by [University of Birmingham] at 04:42 06 November 2015

2.

Results

Table 3 presents mean amplitudes of response on Trial 1 and the Test Trial for Ss in the four experimental conditions. A three way analysis of variance with repeated measures indicated a significant main effect for trials, P (1, 16) = 6.48, p < .05,and a trials by training conditions interaction, F (1, 16) = 4.99, p < .05.No other main effects or interactions proved significant. These results indicated that whereas there was a marked decline in response in the constant training series, there was little change under the incremental series. 3.

Discussion

Groves and Thompson argued that the ISIE was a general parametric feature of habituation and one difficult to account for in terms of the widely accepted theory of habituation proposed by Sokolov. While our previous study and Experiment 1 reported here generally supported that view, the present results contradict it in that they fail to show the ISIE with intensity levels commonly employed in studies of habituation of human physiological response, and are in fact consistent with the theory advanced by Sokolov (9). According to Sokolov’s theory, a change in the characteristics of a stimulus such as an increase in intensity should evoke an orienting response. Aseries of stimuli in which the intensity is continually varying should thus fail to produce habituation, since an orienting response continues to be evoked. The data in Table 3 fit such an interpretation. The discrepancy between the present results and those reported previously may be a function of the intensity of the test stimulus. As argued above, the ISIE may only be a feature of response to aversive stimulation. Unpublished data on heart rate to various intensities of the noise burst employed in our studies indicate that only above 80 d b is the short latency cardiac acceleration-considered a component of startle (3)-reliably elicited. It was TABLE 3 MEANAMPLITUDE OF SCR IN MICROMHOS ON TRIAL I AND THE TESTTRIAL FOR SUBIECTS IN THE FOURTRAINING CONDITIONS IN EXPERIMENT2 Intensity level 60 db 80 db

Constant series Trial 1 Test trial ,0072 .OW3

Incremental series Trial 1 Test trial

.oO04

,005 1

,0031

.o001

,0026

,0038

Downloaded by [University of Birmingham] at 04:42 06 November 2015

J. G. O’GORMAN A N D R. D. JAMIESON

153

with the startle response that the ISIE was first demonstrated, and it may in fact apply only to components of this response pattern. Its generality is at least suspect as a result of this study. One other possible basis for the discrepancy is the nature of the response measure employed. In the present study, magnitude of response to the test stimulus was employed, since trial blocks were short. In the earlier studies showing the ISIE a response frequency measure was employed. Thompson, Groves, Teyler, and Roemer (10) argued that the central process of habituation is better reflected in a response frequency measure than in an amplitude measure, since the latter includes the effects of sensitization. The force of the distinction is weakened however by the finding of a n ISIE with a magnitude measure in the first experiment reported here.

D.

CONCLUSION

The results of our several studies suggest that the ISIE is a feature of electrodermal responding where stimulus conditions are such that habituation is neither rapid nor stable. In such circumstances incremental training is likely to be an effective method of producing response decrement. Where habituation to the stimulus is rapid, it is difficult to show differences between training conditions and little point is served by incremental training.

REFERENCES DAVIS,M . , & WAGNER,A. R. Habituation of startle response under incremental sequence of stimulus intensities. J. Cornp. G Physiol. Psychol., 1969, 67, 486-492. 2. GRAHAM, F. K . Habituation and dishabituation of responses innervated by the autonomic nervous system, In H . V. S. Peeke & M. J. Herz (Eds.), Habituation (Vol. I ) . New York: Academic Press, 1973. Pp. 163-218. 3 . GRAHAM,F . K . , & SLABY,D. A. Differential heart rate changes to equally intense white noise and tone. Psychophysiology, 1973, 10,347-362. R. Habituation: A dual process theory. Psychol. Rev., 1970, 4 . GROVES,P. H., &THOMPSON, 1.

77,419450. 5.

O’GORMAN,J . G . Overextinction of the orienting response. Conditional Reflex, 1970, 5, 27-35.

. Latency and habituation of the electrodermal response. Psychophysiology, 197 1,8,

6. 280.

7. 8.

9.

O’GORMAN,J. G . , & JAMIESON,R. D. The incremental stimulus intensity effect and habituation of autonomic responses in man. Physiol. Psychol., 1975, 3,385-389. SIDDLE,D. A. T . , FOGGITT, R. A,, & NICOL, A. R. Individual differencesin overextinction of the SCR component of the orienting response. Biol. Psychol., 1973, 1, 53-61. SOKOLOV, E. N. The modeling propertiesof the nervous system. In M. Cole & I. Maltzman (Eds.), A Handbook of Contemporary Soviet Psychology. New York: Basic Books, 1969. Pp. 671-704.

154 10.

JOURNAL OF GENERAL PSYCHOLOGY

THOMPSON, R. F., GROVES, P. M . , TEYLER, T . J . , & ROEMER,R. A. A dual process theory of habituation: Theory and behavior, In H. V . S. Peeke & M. J. Herz (Eds.),Habituation (Vol. 1). New York: Academic Press, 1973. Pp. 239-272.

Downloaded by [University of Birmingham] at 04:42 06 November 2015

Department of Psychology The University of New England Armidale, N . S .W . , Australia

Further observations on the incremental stimulus intensity effect and habituation of the human electrodermal response.

The Journal of General Psychology ISSN: 0022-1309 (Print) 1940-0888 (Online) Journal homepage: http://www.tandfonline.com/loi/vgen20 Further Observa...
589KB Sizes 0 Downloads 0 Views