Physiology & Behavior, Vol. 21, pp. 511-514. Pergamon Press and Brain Research Publ., 1978. Printed in the U.S.A.
Effects of a Varying Stimulus Context on Habituation and Sensitization of the O R 1 JOHN F. CONNOLLY 2
Laboratory of Neuro-psychophysiology, Department of Psychiatry, Charing Cross Hospital London, England AND CHRISTOPHER
D. F R I T H
Department of Psychiatry, ClinicalResearch Centre, Harrow, Middlesex, England ( R e c e i v e d 23 M a r c h 1978) CONNOLLY, J. F. AND C. D. FRITH. Effects o f a varying stimulus context on habituation and sensitization o f the OR. PHYSIOL. BEHAV. 21(4) 511-514, 1978.--Twelve male subjects were tested in an experiment which investigated the habituation and sensitization processes of the orienting response (OR) in a varying stimulus context. Visual stimuli which varied along information and contour dimensions were presented in four blocks of 10 stimuli each. A tone served as the sensitizing stimulus and was presented before the fourth stimulus in each block. In two blocks the 5th, 6th and 7th stimuli were omitted ("blanks" condition) while in the other two blocks all stimuli were presented("no blanks" condition). OR frequency and skin conductance levels indicated that the tone produced sensitization. Despite this, there was no evidence of dishabituation to the following stimuli. OR frequency to the 8th stimulus was significantly higher if the preceding three stimuli had been omitted. This result does not support a dual-process theory of habituation. However, rather than being contradictory, these findings are interpreted as further demonstration that laws governing habituation processes during repeated presentations of an identical stimulus do not apply in a context of repeated presentations of a varying stimulus.
Orienting response
Habituation
Sensitization
PREVIOUS observations on the habituation o f the human electrodermal orienting response (OR) suggested that the laws governing OR recovery and dishabituation during identical stimulus series could be different when the habituation series consisted of varying stimuli [2]. F o r example, after OR recovery to a test stimulus there was no dishabituation to immediately following stimuli. This experiment was intended to study further the issues of OR recovery and dishabituation in a varying stimulus context (a situation which more closely approximates the extralaboratory environment) using a design described by Groves and Thompson [3]. Briefly, they studied sensitizationhabituation processes to repeated identical stimulus presentations in both the spinal cat and the intact rat. There were two experimental conditions used in the research with the spinal cat: one in which presentation of the habituation stimulus was continued after the sensitization stimulus and one in which the habituation stimulus was presented once immediately after sensitization. Results showed that response to a stimulus 5 sec after sensitization was independent of the presence or absence of stimulation during that 5 sec. Results with the intact rat supported these findings with an ISI of 60 sec instead of 5 sec. However, generalization
Skin conductance
from an acute preparation to an intact organism was restricted because only one of the conditions (i.e., habituation stimulus presented only once immediately after sensitization) was used in both experiments. The other condition used with the rat did not involve a sensitization stimulus or the omission of any stimuli. Thus, it was not possible to say categorically that the response to renewed stimulation was independent of stimulation in the intervening 60 sec. The design of the present experiment followed the paradigm used with the spinal cat, except that the intervening period was approximately 60 sec. According to the dual-process theory it would be expected that after sensitization the electrodermal OR should be independent of any interim stimulation. If such a result is not found it would provide further evidence of a different set of habituation laws operating during varying stimulus sequences.
METHOD
Experimental Design Details of the method have been presented elsewhere [2].
~This work was conducted at the Department of Psychology, Institute of Psychiatry, London, England.
2N. W. Thames Regional Health Authority Fellow. Send reprint requests to Laboratory of Neuro-psychophysiology, Department of Psychiatry, Chafing Cross Hospital, Fulham Palace Road, London, W.6 8RF, England.
C o p y r i g h t © 1978 B r a i n R e s e a r c h P u b l i c a t i o n s Inc.--0031-9384/78/100511-04502.00/0
512
CONNOLLY AND FRITH
Briefly the 12 subjects were divided into two equal groups half of whom (the H L group) received 10 presentations (hereafter, Trials) of stimuli of high contour and high information followed by 10 stimuli of low contour and low information (Fig. 1). The other half of the sample (the L H group) had this order reversed. Habituation should be firmly established before investigating sensitization effects. Therefore, 12 subjects were used who had already been exposed to a number of presentations of the stimuli and whose response levels had reached asymptote. Five see before Trial 4, subjects heard a tone of I000 Hz frequency and monaural intensity of 60 dB (re. 0.0002 dyne/cm 'z) as rated by a Dawe's sound level meter (No. 1400 F) placed against the earphones. The tone was presented binaurally. All subjects received the usual stimulus at Trial 4. Trials 5, 6 and 7 in both series were presented normally to the L H group but were omitted from both series presented to the H L group. Both groups received the usual stimuli at Trials 8, 9 and 10. This entire procedure was repeated with the L H group now having the stimuli omitted from both series while the H L group received all stimuli. Series in which Trials 5, 6 and 7 were omitted are referred to as " b l a n k s " and series in which they were presented normally are termed " n o blanks." Thus, each subject was exposed to four stimulus runs with a tone in each run. By this time there were a large number of occasions when the subjects did not respond to the stimuli resulting in a highly skewed distribution of response frequency. We therefore
-*
•
A l ' . .
•
used nonparametric statistics to make the within subject comparisons and have presented the data graphically in terms of response frequencies. Stimulus duration was 1.0 sec and the interstimulus interval (ISI) was 17.0 sec. A rest interval of 60.0 sec separated the two stimulus series. Slide presentation was controlled by a Linc-8 computer.
Procedure Subjects were told to simply watch the stimulus presentation and that there would be a recognition task at the end. Subjects were presumed to be "extrinsically motivated" [1] by these instructions. Subjects sat in a darkened sound attenuated room one meter from screen upon which stimuli were back projected.
Apparatus and Data Reduction Skin resistance (SR) was recorded on a system described by Venables and Martin (1967) using a constant current of 10 /zA/cm 2 and was changed to conductance units by taking the reciprocal. Ag-AgCI electrodes (1 cm dia.) were attached to the medial phalanx of the first and second fingers of the left hand. Adhesive collars (1.10 cm dia.) prevented the spread of the electrolyte (Johnson & Johnson K-Y lubricating jelly). A phasic change in SR was considered a response if it occurred in the interval of 0.8 to 4.0 see after stimulus onset.
*"
A
* "
*
"1
~
"
r
•
- "
J,
"
,
:.'..*15' ,.---~,,.
. , , r,,,~
FIG. 1. Examples of the two types of visual stimuli. Upper row: Low contour/low information. Lower row: High contour/high information.
STIMULUS CONTEXT, HABITUATION AND SENSITIZATION
513
RESULTS Results were averaged over the two stimulus types (i.e., high contour-high information and low contour-low information) because they did not produce significantly different results. Also, results concerned with responses to the tone are averaged across the four tone presentations each subject received. Figure 2 shows response frequency averaged across the four blocks of ten stimuli. There were no significant differences between the "blanks" and "no blanks" conditions for the first four trials so trial means for both conditions were combined. The tone produced a large increase in response frequency (Wilcoxon pairs test, T=0, N = 12, p
Effects of a Varying Stimulus Context on Habituation and Sensitization of the O R 1 JOHN F. CONNOLLY 2
Laboratory of Neuro-psychophysiology, Department of Psychiatry, Charing Cross Hospital London, England AND CHRISTOPHER
D. F R I T H
Department of Psychiatry, ClinicalResearch Centre, Harrow, Middlesex, England ( R e c e i v e d 23 M a r c h 1978) CONNOLLY, J. F. AND C. D. FRITH. Effects o f a varying stimulus context on habituation and sensitization o f the OR. PHYSIOL. BEHAV. 21(4) 511-514, 1978.--Twelve male subjects were tested in an experiment which investigated the habituation and sensitization processes of the orienting response (OR) in a varying stimulus context. Visual stimuli which varied along information and contour dimensions were presented in four blocks of 10 stimuli each. A tone served as the sensitizing stimulus and was presented before the fourth stimulus in each block. In two blocks the 5th, 6th and 7th stimuli were omitted ("blanks" condition) while in the other two blocks all stimuli were presented("no blanks" condition). OR frequency and skin conductance levels indicated that the tone produced sensitization. Despite this, there was no evidence of dishabituation to the following stimuli. OR frequency to the 8th stimulus was significantly higher if the preceding three stimuli had been omitted. This result does not support a dual-process theory of habituation. However, rather than being contradictory, these findings are interpreted as further demonstration that laws governing habituation processes during repeated presentations of an identical stimulus do not apply in a context of repeated presentations of a varying stimulus.
Orienting response
Habituation
Sensitization
PREVIOUS observations on the habituation o f the human electrodermal orienting response (OR) suggested that the laws governing OR recovery and dishabituation during identical stimulus series could be different when the habituation series consisted of varying stimuli [2]. F o r example, after OR recovery to a test stimulus there was no dishabituation to immediately following stimuli. This experiment was intended to study further the issues of OR recovery and dishabituation in a varying stimulus context (a situation which more closely approximates the extralaboratory environment) using a design described by Groves and Thompson [3]. Briefly, they studied sensitizationhabituation processes to repeated identical stimulus presentations in both the spinal cat and the intact rat. There were two experimental conditions used in the research with the spinal cat: one in which presentation of the habituation stimulus was continued after the sensitization stimulus and one in which the habituation stimulus was presented once immediately after sensitization. Results showed that response to a stimulus 5 sec after sensitization was independent of the presence or absence of stimulation during that 5 sec. Results with the intact rat supported these findings with an ISI of 60 sec instead of 5 sec. However, generalization
Skin conductance
from an acute preparation to an intact organism was restricted because only one of the conditions (i.e., habituation stimulus presented only once immediately after sensitization) was used in both experiments. The other condition used with the rat did not involve a sensitization stimulus or the omission of any stimuli. Thus, it was not possible to say categorically that the response to renewed stimulation was independent of stimulation in the intervening 60 sec. The design of the present experiment followed the paradigm used with the spinal cat, except that the intervening period was approximately 60 sec. According to the dual-process theory it would be expected that after sensitization the electrodermal OR should be independent of any interim stimulation. If such a result is not found it would provide further evidence of a different set of habituation laws operating during varying stimulus sequences.
METHOD
Experimental Design Details of the method have been presented elsewhere [2].
~This work was conducted at the Department of Psychology, Institute of Psychiatry, London, England.
2N. W. Thames Regional Health Authority Fellow. Send reprint requests to Laboratory of Neuro-psychophysiology, Department of Psychiatry, Chafing Cross Hospital, Fulham Palace Road, London, W.6 8RF, England.
C o p y r i g h t © 1978 B r a i n R e s e a r c h P u b l i c a t i o n s Inc.--0031-9384/78/100511-04502.00/0
512
CONNOLLY AND FRITH
Briefly the 12 subjects were divided into two equal groups half of whom (the H L group) received 10 presentations (hereafter, Trials) of stimuli of high contour and high information followed by 10 stimuli of low contour and low information (Fig. 1). The other half of the sample (the L H group) had this order reversed. Habituation should be firmly established before investigating sensitization effects. Therefore, 12 subjects were used who had already been exposed to a number of presentations of the stimuli and whose response levels had reached asymptote. Five see before Trial 4, subjects heard a tone of I000 Hz frequency and monaural intensity of 60 dB (re. 0.0002 dyne/cm 'z) as rated by a Dawe's sound level meter (No. 1400 F) placed against the earphones. The tone was presented binaurally. All subjects received the usual stimulus at Trial 4. Trials 5, 6 and 7 in both series were presented normally to the L H group but were omitted from both series presented to the H L group. Both groups received the usual stimuli at Trials 8, 9 and 10. This entire procedure was repeated with the L H group now having the stimuli omitted from both series while the H L group received all stimuli. Series in which Trials 5, 6 and 7 were omitted are referred to as " b l a n k s " and series in which they were presented normally are termed " n o blanks." Thus, each subject was exposed to four stimulus runs with a tone in each run. By this time there were a large number of occasions when the subjects did not respond to the stimuli resulting in a highly skewed distribution of response frequency. We therefore
-*
•
A l ' . .
•
used nonparametric statistics to make the within subject comparisons and have presented the data graphically in terms of response frequencies. Stimulus duration was 1.0 sec and the interstimulus interval (ISI) was 17.0 sec. A rest interval of 60.0 sec separated the two stimulus series. Slide presentation was controlled by a Linc-8 computer.
Procedure Subjects were told to simply watch the stimulus presentation and that there would be a recognition task at the end. Subjects were presumed to be "extrinsically motivated" [1] by these instructions. Subjects sat in a darkened sound attenuated room one meter from screen upon which stimuli were back projected.
Apparatus and Data Reduction Skin resistance (SR) was recorded on a system described by Venables and Martin (1967) using a constant current of 10 /zA/cm 2 and was changed to conductance units by taking the reciprocal. Ag-AgCI electrodes (1 cm dia.) were attached to the medial phalanx of the first and second fingers of the left hand. Adhesive collars (1.10 cm dia.) prevented the spread of the electrolyte (Johnson & Johnson K-Y lubricating jelly). A phasic change in SR was considered a response if it occurred in the interval of 0.8 to 4.0 see after stimulus onset.
*"
A
* "
*
"1
~
"
r
•
- "
J,
"
,
:.'..*15' ,.---~,,.
. , , r,,,~
FIG. 1. Examples of the two types of visual stimuli. Upper row: Low contour/low information. Lower row: High contour/high information.
STIMULUS CONTEXT, HABITUATION AND SENSITIZATION
513
RESULTS Results were averaged over the two stimulus types (i.e., high contour-high information and low contour-low information) because they did not produce significantly different results. Also, results concerned with responses to the tone are averaged across the four tone presentations each subject received. Figure 2 shows response frequency averaged across the four blocks of ten stimuli. There were no significant differences between the "blanks" and "no blanks" conditions for the first four trials so trial means for both conditions were combined. The tone produced a large increase in response frequency (Wilcoxon pairs test, T=0, N = 12, p
