psychophysiology of self-regulated phobic thoughts
TRANSCRIPT
BEHAVIOR THERAPY 8, 1 5 0 - 1 5 9 (1977)
Psychophysiology of Self-Regulated Phobic Thoughts
JERRY R. MAY
School of Medical Sciences, University of Nevada, Reno
The responses of 12 phobic subjects to both phobic and nonphobic thoughts were compared with responses of 12 nonphobic subjects to the same conditions. The stimulus for both groups of subjects was a self-generated subvocal statement. This was followed by an interval in which the subject formed an image of the stimulus. The only external cue during the time-locked procedure was a tone which signaled the subject when to produce the statement and the image. The results suggest that internally elicited cognitive activity and physiological re- sponses are major components in the expression of fear. The results provide substantive evidence that self-regulated thoughts have pronounced effects on an individual's physiological and psychological functioning and have implications for the self-regulation therapies.
Fear has been defined as "an emotion of violent agitation or fright in the presence (actual or anticipated) of danger or pain" (English & English, 1958). The anticipatory element in such a definition implies that cognitive factors such as internally evoked thoughts, beliefs, and values may play a significant role in the evolution, maintenance, and elimination of fear. The past decade has revealed a renewed interest in complex cognitive pro- cesses, the ability to recall the past or anticipate the future, and the importance of these characteristics (Beck, 1970; Ellis, 1962; Goldfried & Merbaum, 1973). Lazarus (1971, p. 181) has pointed out that : "Nearly all instances of unhappiness are due to internal thoughts rather than external events. It is seldom other people or external events cause unhappiness. People define various annoyances or danger as 'very upsetting' and then proceed to make themselves 'very upset.' "
While a large body of literature has developed investigating the rela- tionship between external stimuli and autonomic nervous system re- sponding (Craig, 1968; Greer, 1966; Grossberg & Wilson, 1968; Lang,
This study is based on one of two experiments of a dissertation submitted in partial fulfillment of the requirements for a Ph.D. degree in clinical psychology from Bowling Green State University. The author expresses his appreciation to Harold J. Johnson for his supervision and critical reading of the manuscript, to Diane Crunkilton and Phillis Quilter for their assistance in scoring the data, and to William Hudspeth. Requests for reprints should be directed to Jerry R. May, Division of Behavioral Sciences, School of Medical Sciences, University of Nevada, Reno, NV 89507.
150
Copyright © 1977 by Association for Advancement of Behavior Therapy. All rights of reproduction in any form reserved. ISSN 0005-7894
SELF-REGULATED THOUGHTS 151
Me lamed , & Har t , 1970), little bas ic r e sea rch effort has b e e n devo ted to the s tudy of se l f - regula ted in te rna l ly e v o k e d thoughts and a u t o n o m i c n e r v o u s sys t em ac t iv i ty (Schwar tz , 1971; May & J o h n s o n , 1973), pe rhaps because of the diff iculty in deve lop ing an adequa t e methodology . Schwar tz (1971) i n t r o d u c e d a t ime- locked t echn ique to s tudy se l f - induced thoughts . First , the sub jec t memor i ze d the s t imulus mater ia l pr ior to the
expe r imen t . Then , the se l f - induced thoughts were paced by a signal so that the t ime- locked a u t o n o m i c changes could be m e a s u r e d in the same fash ion as changes to ex te rna l s t imuli . The p rocedure a l lowed the subjec t to gene ra t e the s t imulus in te rna l ly , choose the order ahead of t ime, and cont ro l w h e n he wou ld p roduce a thought .
May and J o h n s o n (1973) made several me thodo log ica l changes , cont ro l -
ling for s t imulus complex i ty and ins t ruc t iona l sets. T h e y d e m o n s t r a t e d that se l f - regulated in t e rna l ly evoked s t ressful thoughts p r o d u c e d grea ter phys io logica l changes t han s imilar ly evoked nons t r e s s fu l or re laxing thoughts . H o w e v e r , it wou ld be p r e m a t u r e to c o n c l u d e that , wi th in a cl inical popu la t ion , i n t e rna l ly evoked phob ic thoughts wou ld p roduce greater per iphera l changes than n o n p h o b i c thoughts , The p re sen t experi -
m e n t was des igned to c o m p a r e a u t o n o m i c ne r vous sys t em re spond ing in phobic and nonphob i c sub jec t s to in t e rna l ly evoked thoughts of phobic and n o n p h o b i c con ten t .
METHOD Subjects. One thousand female undergraduates were given a Fear Survey Schedule and
the Snake Questionnaire. This procedure was similar to that reported by Land, Melamed, and Hart (1970). Subjects who rated their fear of snakes as "much" or "very much" on the Fear Survery Schedule and obtained a score of 18 or more on the Snake Questionnaire, and subjects who rated their fear of snakes as "none" on the Fear Survey Schedule and obtained a score of 4 or less on the Snake Questionnaire, were asked to take part in an additional phase of the experiment. Upon arrival at the laboratory the subject was seated in a chair at the end of a 20-foot-long track. She was asked if she would allow the experimenter to bring a harmless 4-foot corn snake enclosed in a transparent box into the room and place it on a platform at the opposite end of the track from her. The platform was motorized and the subject controlled the movement of the box down the track by pressing or releasing a small button on the arm of the chair. This served as the behavioral avoidance test for the experiment3
Twelve subjects who had met the other criteria for phobic behavior and who refused to approach within at least 4 feet of the snake cage were assigned to the phobic group. Twelve subjects who had met the other criteria for nonphobic behavior and touched and picked up the snake were selected for the nonphobic group.
Apparatus. The subject and the experimenter were housed in two electrically shielded and sound-attenuated rooms. The subject was seated in a large overstuffed reclining chair and was observed via closed circuit television. A 60 db/1300 Hz tone presented through ear- phones served as the time-locked cue. Onset of the sequence of tones was controlled by the experimenter. The duration of the tone, 250 msec at 10-sec intervals, was controlled by
The behavioral avoidance test apparatus was designed and provided by James E. Hastings.
152 JERRY R. MAY
Behavioral Research Systems solid-state programming equipment. The subject terminated the series of tones by pressing a small pushbutton attached to the arm of the chair.
Dependent variables. A Grass Model 7B polygraph recorded the physiological responses. Heart rate was monitored through attachment of German silver electrocardiogram elec- trodes, Type II placement. Two Beckman biopotential skin electrodes (16 mm diam) were attached to the volar surface of the third and fourth finger of the right hand to measure electrodermal responses. Respiration was recorded with a strain gauge transducer attached to an elastic band around the subject 's chest.
Design. The subjects were assigned to two groups. Group 1 consisted of snake phobic subjects and group 2 consisted of nonsnake phobic subjects. Both groups experienced 10-sec stimulus block (subvocal statement about a snake or nonsnake stimulus) followed by a 10-sec image block (visual image of the stimulus). There were eight snake stimulus trials alternated with eight nonsnake trials.
Procedure. Subjects who had met the criteria of the Fear Survey Schedule, Snake Questionnaire, and Behavioral Avoidance Test and had agreed to continue in the research project were scheduled for an additional appointment. Upon arrival at the laboratory the subject was given a brief explanation of psychophysiology and the response measures. She was also told that she would be hearing a sequence of low-intensity tones and would be asked to learn a series of numbers and sentences. Recording sensors were attached and the same instructions were given to all subjects regardless of their group.
Each subject was told that during each trial she would be hearing a sequence of tones every 10 sec through earphones. The experimenter initiated the tone and the subject terminated a sequence of tones by pushing a button. The subject was instructed that when the tones began she was to think a series of numbers, a simple sentence, and to produce an image to the sentence. She terminated a trial by pushing a button after the tone following the image block. She was instructed to think only one number, sentence, or image during each block between the tones. The series of numbers was simply 1, 2. The sentences were: (1) "I see a girl laying on a couch with a snake crawling on her," (2) "I see a girl laying on a couch, holding and reading a magazine," (3) " I see a girl sitting in a chair with a snake crawling on her," (4) "I see a girl sitting in a chair holding and reading a magazine." She was to vary the repetition of the number series up to three times; however, she was to think the sentence and image once. Varying the repetition of tones allowed the subject to have self-control over the onset of the sentences. An example of a trial would be: (beep) think 1, (beep) think 2; (beep) think 1, (beep) think 2, (beep) think 1, (beep) think 2, (beep) think "I see a girl laying on a couch with a snake crawling on her," (beep) produce an image to that sentence (beep) push button which terminates the tones and signaled an end of a trial to the experimenter. After the tone was reinitiated by the experimenter, the subject began the next trial, e.g., number series, next sentence, and the i m a g e / T h e intertrial interval varied from 30 to 90 sec with a mean of 60 sec.
Two orders of stimulus presentation were used in the experiment between subjects: (1) snake, nonsnake, snake, nonsnake; and (2) nonsnake, snake, nonsnake, snake. The entire experiment consisted of a total of 16 trials. Prior to leaving the subject 's room she was reminded that she should vary the number of times she repeated the series of numbers preceding each sentence. In addition, the experimenter asked the subject to recall the sentences. A 10-min adaptation period preceded the onset of the experiment.
Following the session, the subject filled out a questionnaire to assess her subjective rating of her ability to form images to each of the stimuli and their vividness and emotional intensities. Finally, on a separate day, each subject was readministered the Behavioral Avoidance Test.
2 Complete instructions may be obtained from the author.
S E L F - R E G U L A T E D THOUGHTS 153
RESULTS
Selection of Subjects
For group 1, the Snake Questionnaire score was 22.5 and the Pre- and Post-Behavioral Avoidance Test scores, measured in feet from the snake, were 15.08 and 13.25, respectively. For group 2 the Snake Questionnaire score was 2.67 and all subjects picked up the snake during the Pre and Post Behavioral Avoidance Test.
Heart Rate
Heart rate was measured in beats per minute and calculated on a second to second basis from: (a) the onset of the final series of numbers preceding the onset of each stimulus block, (b) throughout the 10-sec stimulus block (subvocal statement), and (c) during the 10-sec image block. The number series served as a baseline. A difference score for each second of a stimulus and image block was then derived by subtracting a mean score based on the final series of number stimuli from each of the 10 stimulus and 10 image block scores.
Separate split plot factorial analyses of variance (Kirk, 1968), with re- peated measure on three dimensions were carried out on the heart rate data for the stimulus and image blocks. The components of each analysis were: groups (phobic and nonphobic), conditions (snake and nonsnake), trials (1-8), and time (1-10 sec). Mean differences for significant interac- tions wers examined by Tukey's HSD test for multiple comparisons (see Table 1).
The analysis of the stimulus block demonstrated the heart rate respond- ing was greater for the phobic subjects than for the nonphobic subjects, F (1, 22) = 4.69,p < .05. A significant time effect, F (9, 198) = 8.96,p < .01, revealed a general orienting response. Mean changes were greatest for the phobic subjects, producing the statement about the snake. No other stimu- lus block heart rate difference was significant.
The results of the analysis of the image block indicate that heart rate responses were again greater for the phobic group than the nonphobic group, F (1, 22) = 16.92, p < .01. More specifically, the groups x conditions interaction, F (1, 22) = 19.82, p < .01, showed that heart rate responses were greater for phobic subjects imagining themselves with a snake (see Table 1). Slight habituation across trials was found, F (7, 154) = 3.55, p < .01, but responding by the phobic subjects to the snake stimuli did not return to baseline (see Fig. 1). A significant time effect, F (1, 198) = 12.82, p < .01, indicated pronounced heart rate arousal to internally elicited images, which reached a maximum point at about the 4th sec of the 10-sec trial.
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SELF-REGULATED THOUGHTS 155
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Flc. 1. Mean heart rate difference scores for group 1 (phobic) and group 2 (nonphobic) subjects and the subconditions (snake and nonsnake stimuli) across blocks of trials for basal level (B), the stimulus block (S), and the image block (I).
Respiration Rate and Amplitude
Respiration rates were calculated: (a) for the final series of numbers preceding the onset of each stimulus block, (b) through the 10-sec stimu- lus block, and (c) through the 10-sec image block. Respiration amplitude (in millimeters) was measured as the peak to peak amplitude of each respiratory cycle for the same period. Changes in respiration rate and amplitude were derived by subtracting the mean score based on the last two number series from the mean score for each stimulus and image block.
The three-way analyses of variance for the stimulus block for respira- tion rate revealed a significant groups x condition interaction, F (1, 22) = 4.64, p < .05; however, the mean differences were not significant (see Table 1). The three-way analysis for the image block for respiration rate revealed no significant differences.
The analysis of variance of the stimulus block for respiration amplitude revealed a significant groups x conditions interaction, F (1, 22) --- 4.45, p < .05, but failed to demonstrate any significant mean differences. Mean comparisons of the significant groups × conditions interaction, F (1, 22) = 17.75, p < .01, for the image block revealed that respiration amplitude was greater for the phobic subjects while producing an image to the snake stimuli (see Table 1). The lack of a significant trials effect indicated no evidence or habituation for respiration amplitude (see Fig. 2).
Skin Conductance Level and Galvanic Skin Response (GSR) Frequency
Electrodermal activity was recorded in skin resistance and converted to log conductance. Skin conductance level was sampled every 10 sec for
156 JERRY R. MAY
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FIG. 2. Mean respiration amplitude difference scores for group I (phobic) and group 2 (nonphobic) subjects and the subconditions (snake and nonsnake stimuli) across blocks of trials for basal level (B), the stimulus block (S), and the image block (I).
the same time period as the other physiological responses. GSR fre- quency was calculated in the same manner as respiration rate. A GSR was measured as a change which reached at least 500 ohms with a maximum rise time of 2 sec. Responses that met this criterion were counted. Differ- ence scores for skin conductance level and GSR frequency were derived in the same manner as those for respiration r a t e and amplitude.
A three-way analysis of the stimulus block for skin conductance failed to reveal any significant differences. The analysis for the image block indicated that responses were larger for the phobic subjects than the nonphobic subjects, F (1, 22) = 6.74, p < .05.
A three-way analysis of variance for the stimulus block for GSR fre- quency demonstrated that the phobic group had a higher rate of re- sponses than the nonphobic group, F (1, 22) = 8.63, p < .01. The similar analysis for the image block revealed that the snake stimuli produced more responses than the nonsnake stimuli, F (1, 22) = 10.55, p < .01. Both the analyses of skin conductance level and GSR frequency failed to reveal significant interaction effects. In addition, mean values of the electrodermal responses did not differentiate the phobic subjects imaging themselves with the snake from the other conditions.
Post-Experimental Questionnaire All subjects subjectively rated their ability to form vivid images and
their emotional react ion to the stimuli on separate scales. There was no significant difference between groups or between subconditions on the subject 's ratings of their ability to form vivid images. The phobic subjects did rate their emotional reaction to the snake stimuli as larger than the
SELF-REGULATED T H O U G H T S 157
nonphobic subjects. These ratings further substantiate that proper selec- tion was used in grouping the subjects and the stimuli used in the experi- ment were appropriate. An interesting finding extracted from the ques- tionnaire was that eight of the phobic subjects and five of the nonphobic subjects reported experiences in other sensory modalities while produc- ing visual images. Tactile and auditory modalities were the most fre- quently mentioned.
DISCUSSION
Self-regulated phobic thoughts produce greater physiological activity than similarly induced nonphobic thoughts. Also, phobic subjects reacted to these thoughts more than nonphobic subjects. It is obvious that the central nervous system is necessary in the perception and cognitive processing of fear. In addition, it appears that both the central nervous system and the autonomic nervous system interact significantly to influ- ence an individual's experience of fear. In the current study, manipulation of internally elicited cognitive events led to marked changes in autonomic activity and subjective reports.
The results support the finding of May and Johnson (1973). The present experimental conditions produced even larger magnitude differ- ences. The comparison of responses between phobic and nonphobic individuals in a strictly controlled experiment extends the findings toward clinically relevant populations. The present design allowed a longer period of time for self-regulated stimulus input, i.e., the stimulus block followed by the image block. This provided a more analogous situation to the obsessive and ruminative process observed in the production of symptoms within phobic individuals.
Again, heart rate was found to be sensitive to an internally elicited cognitive task. Respiration amplitude patterned heart rate changes quite closely, but electrodermal activity was contrary to results employing externally presented fearful stimuli (Greer, 1966; Grossberg & Wilson, 1968; Lang, Melamed, & Hart, 1970; Van Egeren, 1971). This finding, however, replicated the May and Johnson (1973) report that electroder- mal activity was not very sensitive to internally evoked stressful thoughts within the time-locked design. Further research employing the time- locked design and comparing internal and external modes of stimulation (May, in press) has empirically substantiated this reported discrepancy between the two modes of stimulation. It may be that electrodermal changes are only related to externally elicited orienting responses, while cardiovascular and respiratory measures are more representative of pro- longed maintenance of a maladaptive symptom.
It should be noted that the present results were obtained even though rather strict control procedures were employed. Not only were responses
158 JERRY R. MAY
compared between phobic and nonphobic subjects, but within subjects through presentation of snake and nonsnake subconditions. The subjects in both groups received identical instructions and the snake, nonsnake subcondition statements within subjects were matched for stimulus com- plexity. The statements were of the same length and the words were similar, except for the final stem, which signaled the subject to think about a snake or a magazine. The neutral stimuli in previous studies have varied from such complex stimuli as a scene of the subject walking slowly on a summer day to geometric shapes. Visualization of landscapes has been used frequently as a neutral condition and some studies have em- ployed unpleasant or stressful stimuli as controls.
The larger differences revealed between the responding during the stimulus and image blocks point to the significance of imagery in the development and maintenance of chronic fear. However, counterbalanc- ing in the present design was impossible, and an order effect could well account for a portion of the difference.
An interesting finding reported by the majority of the phobic subjects was their increased ability to produce vivid visual images and an in- creased emotional experience following repetition of the phobic thought. Also, some subjects found it increasingly difficult to "turn off" the phobic thought. This is quite similar to the phenomena that occur in introspective, ruminative individuals, such as phobic, obsessive, or de- pressed patients seen in clinical settings. These people frequently report continued and uncontrolled repetition of uncomfortable, anxiety provid- ing, unwanted thoughts, and peripheral physiology, e.g., tachicardia and hyperventilation.
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RECEIVED: September 26, 1975 FINAL ACCEPTANCE: March 26, 1976