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Are intrusive thoughts subject to habituation?
Behov. Res. 1 ?-herspy Vol. 18. PP. 409 to 418 Pcrgamon Press Ltd 1980. Printed in Great Britain
ARE INTRUSIVE THOUGHTS SUBJECT TO HABITUATION? L. PARKINSONand S. RACHMAN* Department
of Psychology, Institute of Psychiatry, De Crespigny Park, London, SE5 8AF, England (Received 3 March 1980)
Summary-The main question was addressed by studying three groups of non-psychiatric subjects who experienced intrusive and distressing thoughts. The effects of one of three forms of habituation training (massed, spaced and spaced combined with relaxation) on selected thoughts were assessed on a range of measures including latency, duration, discomfort, fading and so on. It appears that intrusive thoughts are subject to habituation. Broad decrements of significant magnitude were observed after each of three forms of habitation training. However, the occurrence of unpredicted decrements attributable to practice effects and to relaxation, presents some problems of interpretation.
INTRODUCTION
Can we get accustomed to our own thoughts? This odd question loses some of its whimsicality when therapists are asked to help relieve the suffering of patients who are tormented by obsessions. These unwanted and unacceptable thoughts are persistent and can produce considerable distress (Rachman, 1979). The sufferer fails to get accustomed to his tormenting thoughts-in contrast to the normal course of events? What is the normal course of events? Do we ordinarily become accustomed to repetitive thoughts, even those which produce distress? From the practical point of view, it is necessary to know whether deliberate attempts to facilitate habituation to distressing thoughts have any chance of succeeding. The main purpose of this investigation was to determine whether selected aspects of intrusive thoughts are indeed subject to decremental processes akin to habituation. The subsidiary aims were to compare the decremental effects of repeated brief formations of the intrusive thought with the effects of a single extended formation (massed vs spaced), and to determine the effects of relaxation training on the decremental process. C’Intrusive thoughts’ refers here to intrusive thoughts or images-see Rachman and Hodgson (1980).] The impetus for the investigation came from a theory proposed to account for obsessions. Rachman (1971) argued the necessity for assuming that everyone has experiences akin to obsessions, and proposed that obsessional material be construed as (largely internal) noxious stimuli to which the person has failed to habituate. Regarded from the more recent prospective implied by the concept of emotional processing (Rachman, 1980) one can reframe the problems of obsessions, and, indeed, of most unwanted and intrusive thoughts, in such a way as to incorporate them in the category of ‘failures of processing’. Either way one is bound to ask whether intrusive thoughts, even up to the level of obsessions, are subject to decremental processes-and if so, which ones? Nor would it be unrealistic to expect the answers to these questions to lead to practical clinical measures. The elaboration of the original theory of obsessions (see Rachman and Hodgson, 1980) and the framework of emotional processing overlap to an extent and share certain features in respect of the present problem of the decremental processes relating to intrusive thoughts. From both starting points one would be led to predict that intrusive * This research was supported by a grant from the Social Science Research Council. B.R.T. 18/5-D
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thoughts are subject to decremental processes, and that habituation training is likely to facilitate such decrements. In view of the tendency of intrusive thoughts to persist (a major source of distress in the case of obsessions) it is useful to consider the conditions that impede or promote the operation of decremental processes. Analyses of these conditions are given in Rachman (1980) and Rachman and Hodgson (1980), and here we need do no more than quote from the original formulation and some of the ensuing predictions. “Broadly speaking, the patient’s inability to habituate to these ruminative stimuli can be overcome by presenting the noxious stimulus in attenuated form under conditions which favour habituation, or by effecting a direct improvement in mood state” (Rachman 1971, p. 234). In the present study we were concerned with the first part of the statement. Making allowances for the important differences in sample characteristicsthe original predictions were made for clinical obsessions, not as in the present study, the unwanted intrusive thoughts of a non-disturbed sample-these selected predictions are partly relevant : Habituation will be facilitated by calm, equable mood states. Mildly disturbing ruminative thoughts will habituate more quickly with short presentations. During the early stages of habituation training, a temporary increase in the disturbance caused by the ruminations may occur. Regular presentation intervals will speed the process of habituation without ensuring endurance. Under calm conditions, long exposures to highly disturbing ruminative thoughts will result in quicker habituation than short exposures. Under calm conditions, long exposures to ruminative thoughts will result in more enduring habituation than short exposures. Although the present investigation has a bearing on only the first three of these predictions, the additional statements are reproduced in order to provide a fuller background to the study. In the present study we sought evidence of habituation-like decrements, and gathered data on the effects of spacing, and of relaxation. It is worth noticing that in an earlier study, preliminary findings on a small sample suggested that ‘normal obsessions’ formed to instruction were of mild intensity (Rachman and de Silva, 1978) and that with repeated practice, their duration and the accompanying discomfort decreased. The latency of the thought formulation increased. It must be emphasized that in the present study we were again concerned solely with short-term decremental processes. Given a clear demonstration of such short-term effects, the subsequent investigation of lasting decrements should present few problems. Although we recorded and analysed 10 characteristics of each intrusive thought, greatest attention was paid to subjective discomfort. This variable was used as the major indicator of decremental change-habituation. As part of the continuing investigation of the nature and structure of unwanted intrusive thoughts (see Rachman and de Silva, 1978, and Parkinson and Rachman, 1980), we took this opportuinity to look into the possibility that intrusive images might respond slightly differently to our repeated formation procedures (habituation training) than do intrusive thoughts. In sum, the major aim of the study was to determine whether unwanted intrusive thoughts (and images) are subject to habituation-like decremental processes. The subsidiary aims were: to compare the effects of massed and spaced trials, to determine the effects of relaxation training on the decremental processes, and to compare the responsiveness of intrusive images and intrusive thoughts. PROCEDURE In keeping with the aims set out in the Introduction, we examined the decremental effects of three forms of habituation training on selected aspects of intrusive thoughts. The three forms of training consisted of: (a) six trials of 2 minutes duration, each separ-
Are intrusive thoughts subject to habituation?
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ated by a 1 minute rest interval, (b) six trials of a similar duration and spacing, but preceded by relaxation instructions, and (c) one extended trial of 12 minutes duration. The effects of each condition were assessed by within and between group comparisons, using the following selection of measures which were administered before and after the completion of each of the relevant forms of training. For each S, two comparably distressing intrusive thoughts or images were chosen (one as the target thought and the other as the non-treated comparison) and then formed to E’s instructions. The time taken by the S to form the selected thought or image to instruction was recorded (latency). The duration of the thought was recorded in seconds. After removing the thought (or image), the S was asked to rate its characteristics on a O-10 scale (10 is the maximum score)degree of discomfort, degree of stressfulness, unacceptability, intensity, controllability, resistance, anxiety, fading, significance, urge to neutralize, competing thoughts, bodily reactions. After completing the relevant type of habituation training each S was once again asked to form the comparison thought/image and the target thought/image. The latency, duration and characteristics of each thought were recorded as before. Subjects were asked to form the comparison or the target thought/image as clearly and vividly as possible and to signal its formation by raising one finger, and to retain the thought until asked to remove it. The loss of the thought, whether intended or not, was signalled by the S lowering his finger. In the case of the two forms of training comprising six 2 minute trials, the Ss were asked to estimate at the end of each trial the amount of discomfort, unacceptability, stressfulness, etc., they had experienced. Trial by trial data were collected. In all cases, a post-trial enquiry was aimed at assessing whether the S had attempted to neutralize the thoughts. The occasions on which the thoughts faded prematurely were recorded. The three forms of habituation training were: (a) spaced practice consisting of six trials of 2 minutes duration separated by rest pauses of 1 minute, (b) spaced practice, as above, preceded by brief relaxation training and (c) one massed practice trial lasting 12 minutes. The control procedure consisted of identical practice-rest sessions but Ss formed neutral thoughts/images of a blank television screen or of an apple. Each S completed a set of experimental trials and a matched set of control condition trials, with the order of presentation balanced in each of the three groups. Subjects
Sixty normal adults, divided into three equal groups, participated in the study. They were included in the study if they were able to describe at least two distressing intrusive thoughts or images, and were willing to devote roughly 1 hr to the training session and complete the brief tests referred to earlier. Once accepted for the study the Ss were randomly allocated to one of the three forms of training procedures.
RESULTS After habituation training decreased responsiveness was observed on almost all of the measures. Most of these results are illustrated in Figs. 1 and 2. Although the overall pattern of decremental changes was remarkably similar with all three forms of habituation training (repeated brief presentations, repeated brief presentations under relaxation, or one extended presentation), some slight differences were observed. So, for example, some of the decreases observed after repeated spaced presentations were of larger magnitude than those observed after the extended or massed presentation. Furthermore, we obtained clear evidence to show that relaxation training expedites most of the decremental changes. Although the final point reached with spaced presentation, with or without relaxation, was no different, the changes were obtained at different speeds. As can be seen from Fig. 3, the subjective discomfort score reduced very rapidly when the subjects were relaxed before carrying out the habituation training. Among those subjects who carried out these repeated practices without prior relaxation, the same degree of reduction in discomfort was achieved, but at a slower rate. This is perhaps the point at which to
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Are intrusive thoughts subject to habituation? 10
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interpolate, especially for the sake of clinicians, that the introduction of relaxation training was followed by surprisingly quick and large reductions in the discomfort and other measures of unpleasantness reported by subjects when they formed their intrusive thoughts to instruction. Whatever the explanation, the results show that habituation training preceded by relaxation brought about immediate and large changes in discomfort. The stressfulness of the thoughts followed a similar pattern (Fig. 4). Thus far, the results appeared to be straightforward and reassuringly predictable. All three forms of habituation training were followed by widespread reductions in discomfort and associated measures of unpleasantness (Tables l-3). These matters are seldom so Table 1. Mean scores, pre- and post-spaced habituation training, plus preand post-scores for control condition Experimental pre-
Control pre-
Experimental post-
Control post-
19.70 48.70 7.70 6.00 7.05 7.85 5.40 2.45 8.20
17.55 52.25 6.85 5.75 6.65 7.40 4.25 3.10 8.25
29.95 45.60 2.55t 4.50t 2.50t 4.80t 2.45* 5.55t 3.70t
24.40 54.80 6.75* 6.75 6.20 6.85 4.20 4.90* 8.05
Latency (sets) Duration (sets) Discomfort Intensity Stressfulness Unacceptability Resistance Controllability Fear/anxiety
*Indicates significant pre-post difference at 5% level. t Indicates significant pre-post difference at 1% level. Table 2. Mean scores, pre- and post-spaced habituation training plus relaxation, and pre- and post-control condition
Latency (sets) Duration (sets) Discomfort Intensity Stressfulness Unacceptability Resistance Controllability Fear/anxiety * Indicates pre-post t Indicates pre-post
Experimental pre-
Control pre-
10.80 42.65 7.45 7.00 8.40 9.05 7.30 2.40 7.80
19.70 43.90 7.95 7.10 8.35 9.25 7.35 2.35 7.75
Experimental post34.95t
29.85 2.90t 4.65t 3.551 5.55t 2.15t 6.05t 4.50t
difference significant at 5% level. difference significant at 1% level.
Control post28.05* 39.45 4.90* 5.90t 4.45t 5.70t 4.15’ 4.65* 5.85.
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L. PARKINWNand S. RACHMAN Table 3. Mean scores, pre- and post-massed control condition
Latency (sets) Duration (sets) Discomfort Intensity Stressfulness Unacceptability Resistance Controllability Fear/anxiety
habituation
training,
Experimental pre-
Control pre-
Experimental post-
Control post-
11.05 49.60 6.65 6.65 6.55 7.70 4.95 3.05 8.10
14.60 46.15 6.85 6.75 6.95 6.70 5.20 3.85 7.65
13.05 51.50 3.251 5.70* 3.20t 3.80t 2sot 6.20t 5.60t
14.45 51.25 6.05 6.25* 5.4s 5.75 4.75 5.10* 7.40
and
* Indicates significant difference pre-post at 57; level. t Indicates si~ifi~nt difference pre-post at l”,; level.
straightforward and the major surprise in this part of the experimental results emerged when comparisons were made between the various forms of habituation training and the control condition, which, it will be recalled, consisted of repeated formations of a neutral thought image. Somewhat surprisingly, widespread and fairly large decrements in discomfort, etc., were also observed after the completion of the control condition. Indeed, a number of these decrements were as large as those seen after the most successful of the habituation training conditions. It appears that when relaxation is provided, with or without the addition of the specific habituation training procedures, extensive decrements in discomfort are observed. The use of relaxation came close to swamping the effects of habituation training. In the relaxation plus habituation training condition, however, some of the changes observed after treatment were of greater magnitude than those that took place after the control condition. The four measures on which the addition of the specific training was followed by changes of greater magnitude were discomfort, intensity, resistance and controllability. As far as the effects of the control manipulation are concerned, the clearest ‘practice effects’ were observed on the intensity characteristic (which was seen to decrease significantly after control conditions) and the sense of controllability, which was observed to show a significant increase. The surprisingly broad decrements observed after the control condition can be seen in summary form in Table 4. It is evident that the greatest range of improvements were observed after the control condition in which relaxation was used. However, some significant decrements were also observed after control conditions in which relaxation did not feature. It would appear therefore, that we are dealing with two types of ‘non-specific’ influence-a broad effect of relaxation and a narrow effect that appears to be a consequence of repeated experiences of forming the relevant thoughts to instruction. The extent and magnitude of these control condition changes give the clearest possible notice of how important it is to include control m~ipulations in studies of this kind. In the absence of a control conTable 4. Significant decrements observed after completion of the control condition (pre- to post-) for each of the three groups. The 1% level is shown in the table as 0.01, and ST/,as 0.05 Variables Latency Duration Discomfort Intensity Stress Unacceptability Resistance Controllability Anxiety
Spaced training
Spaced plus relax
Massed training
N.S. N.S. N.S. 0.5 N.S. N.S. N.S. 0.5 N.S.
0.01 N.S. 0.0 I 0.01 0.01 0.01 0.01 0.01 0.01
N.S. N.S. N.S. 0.05 0.05 N.S. N.S. 0.05 N.S.
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Are intrusive thoughts subject to habituation?
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Fig. 5. The latency to thought formation increased gradually during spaced training with relaxation (solid line) and without relaxation (broken line).
dition we would certainly have been led to draw erroneous conclusions about the specificity of the changes that might be expected to follow on the use of habituation training procedures. Turning to the comparisons between intrusive images and intrusive thoughts, it has to be admitted that this part of the investigation was fruitless. No major differences in the decremental processes were observed between thoughts and images. Those few differences which did emerge were of small magnitude and failed to form any meaningful pattern. As far as the parameters of latency and duration are concerned, the prediction that latency would increase with repeated trials was confirmed (see Fig. 5). However, the duration of the thought or image showed no significant alterations over the repeated trials. The subsidiary information about changes taking place during the course of habituation training, was largely disappointing. The occurrence of fading appeared not to be affected by the habituation training. The urge to neutralize was not prominent before the introduction of the training and with one exception, was not stimulated by the training procedure. After habituation training, subjects reported a distinct weakening of .their subjective feelings of bodily reactions, i.e. they reported fewer sensations such as trembling, sweating and so on. Whether these subjective reports of changes in bodily reaction reflected actual decreases in sweating and so on, or whether they were the subjects’ interpretations of some other changes, remains to be seen. The effects of the training procedures were also assessed by comparing the changes observed in the target thoughts, pre- and post-training, with the changes observed in the ‘non-treated comparison thoughts. The differential changes in the ‘treated’ and ‘nontreated’ thoughts were not significant on the measures of fading, neutralizing activities or intrusiveness. However, after ‘treatment’, the target thoughts showed a larger reduction in the associated physiological reactions; the ‘non-treated’ thoughts were similarly accompanied by weakened reactions on. retest, but these decrements were significantly smaller than those observed in association with the ‘treated’ thoughts. In one of the three experimental groups, the significance of the target thoughts to the S was seen to diminish. To summarize the findings so far: widespread and significant decrements in responsiveness were observed after habituation training. These changes were observed regardless of the form of the habituation training. There were, however, differences in the speed with which the changes were induced, and the inclusion of relaxation appeared to expedite matters. In answer to the original question, we can affirm that intrusive thoughts are indeed subject to habituation. However, we immediately have to add that significant decrements in responses of this kind are also observed as a consequence of practice effects, and of relaxation training. So, intrusive thoughts are subject to habituation-but they are also subject to a number of other decremental processes. In therapeutic undertakings, due allowance must be made for the operation of those general influences.
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DISCUSSION The first question to be decided is whether or not the decremental processes observed in the course of this study can safely be regarded as a form of habituation. In the restricted definitional sense, the results certainly appear to be reminiscent of an habituation process-repeated presentations of a’stimulus are followed by declining responsiveness. The awkward problem of deciding whether or not it is reasonable to equate the instructions to form the relevant thought with the type of stimulus that features in conventional habituation studies, is difficult to resolve, If indeed, the verbal instruction given to the subject is regarded as equivalent to, say, the auditory stimulus used in habituation experiments, one has merely to contend with the considerably greater complexity of the verbal stimulus. The problems do not end there, however. In the present study, and in its potential applications, we are after all concerned mainly with the thought that is formed to instruction, rather than with the experimenter’s verbal utterance. Once we leave the relatively colorable position of regarding the experimenter’s verbal instruction as a stimulus, one begins to struggle with the seemingly impossible notion that the thought formed in response to such an instruction provides the stimulus to which the person becomes habituated. Hence, the somewhat whimsical question with which this paper opened- “can we get accustomed to our own thoughts?“. Having acknowledged these considerable conceptual difficulties, we can proceed to regard the decremental processes observed in the experiment as being comparable to habituation. If we do so, the first question is why did relaxation so successfully expedite the observed decremental process? Here we can draw attention to the well-substantiated observation that habituation proceeds more successfully at low rather than high levels of arousal (Lader and Wing, 1963). These authors used the observation that relaxation facilitates habituation as the basis for their re-inte~retation of systematic desensitization in terms of an habituation modei. In essence, they argued that densitization is a form of habituation; moreover, Wolpe’s (1958) use of relaxation to facilitate desensitization does no more than facilitate the process of habituation by lowering the subject’s level of arousal. By the same token the use of preliminary relaxation in the present study facilitated the habituation process by lowering the subject’s arousal. It would seem that attempts to facilitate the decline of disturbing thoughts might we11be facilitated by the use of preliminary relaxation-whether one adopts the perspective put forward by Lader and Wing or not. It should also be pointed out that in the present experiment the preliminary use of relaxation appeared to speed up the process of habituation rather than. change its direction or alter its general course. * The subjects who had spaced repetitions of thought formation, even in the absence of preliminary training in relaxation, showed a gradual decremental change. If we follow the Lader and Wing perspective, the present results appear to fall into place reasonably well. However, they do not easily or satisfactorily account for the almost immediate effects of relaxation. It can be seen in Figs. 3 and 4 that those subjects who had preliminary relaxation showed significant decreases at the end of the first 2 min trial. Although this does not rule out the Lader and Wing explanation, the process does seem to have taken place rather too quickly to fit easily into their account. Without discarding their approach to habituation processes, it might be worthwhile considering the operation of additional processes. Can it be that relaxation makes a contribution over and above that of lowering arousal preparatory to habituation? Indeed, can we go further and suggest that the experimental circumstances and implicit demands made non-specific con~butions to the decremental process. This possibility is strongly supported by the finding that a number of significant decrements were observed even in the case of the ‘untreated’ target thoughts. These findings demonstrate the operation of influences other than habituation training. In a related study (Parkinson and Rachman, in preparation) we have found a relationship between the occurrence of an accompanying physiological reaction and difficulty in * A recent report by Borkovec and Sides (Behau. Ref. Ther. 17, 529-540) shows that relaxation can “maximize imagery vividness, autonomic reactivity to the imagery and decline in reactivity over repeated exposures”.
Are intrusive thoughts subject to habituation?
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removing an unwanted intrusive thought. This finding, considered in conjunction with the results of the present study, suggests that: (a) intrusive thoughts accompanied by physiological reactions are difficult to remove, (b) relaxation reduces physiological reactivity and hence (e) relaxation facilitates the removal of disturbing thoughts. Conversely, training procedures such as thought-stopping or habituation training are not likely to modify disturbing thoughts unless the procedures are combined with relaxation training. In pursuit of this possibility, we are attempting to re-assess the published reports of clinical failures in terms of the use made by relaxing procedures. In addition to the general situational influences already noted, it is necessary to take into account the probably significant effect of simple practice. In order to carry out the experiment, or comparable experimental treatments, it is of course necessary to identify a target thought and a comparable thought which remains untreated. Moreover, it is essential to have at least two repetitions of the formation of each of these thoughts, i.e. the treated target thought and the untreated comparison thought. It seems likely that this simple repetition, carried out for purposes of assessment, is a reactive measure. It follows that in order to demonstrate the particular and additional contribution of any experimental manipulation, one needs to use a procedure that is capable of producing effects of some magnitude. Failure to use a powerful intervention may lead to the production of insignificant results in which the practice effects equal those attributable to the experimental intervention, and hence obscure the process of greatest interest. The surprisingly large decremental influence of non-specific situational factors and of practice effects should be borne in mind when designing experiments of this kind, and in particular, when carrying out evaluative trials of new forms of treatment. A failure to include a comparison thought of equal distress value would certainly undermine the value of any experimental study or treatment evaluation. Turning next to our failure to detect any differences between spaced training and massed training, this result suggests that it is the duration of the thought formation that is relevant rather than the frequency with which the thought is formed. Put into more familiar language, it is the duration of the ‘exposure’ rather than the frequency of exposures that seems to be critical, at least in the short-term. Although the procedures and subjects were somewhat different, the results reported by Rabavilas et at. (1976) are comparable. In their treatment of twelve obsessional-compulsive patients, they were able to find no differences in the effects produced by short vs long fantasy exposures. This is perhaps the point at which to observe that these authors also reported a significant decline in the untreated but comparable obsession-consistent with our evidence of some form of practice effect, perhaps combined with non-specific situational influences. If it can be confirmed that the duration of thought formation plays a major role in influencing the speed and shape of decremental processes, this should provide some clues about the nature of the processes involved. A related possibility is that the amount of decrement observed is a function of the duration of ‘non-threatening’ time during which the thought is held. In other words, if a person holds the distressing thought for a certain minimum period he will learn to tolerate it. The process of habituation is perhaps dependent on a minimum amount of non-threatening ‘exposure’ time. The present findings, if confirmed, may be of clinical significance. They are most relevant to the study and modification of obsessions, but may also tell us something about morbid preoccupations, perhaps even jealousy, and conceivably something about anxious brooding, etc. If we accept that the intrusive thoughts dealt with in the present experiment bear a similarity to obsessions, it means that habituation training techniques are worth exploring (see, for example, Rachman, 1979), and that relaxation is a desirable prerequisite. It might also follow that habituation preceded by relaxation is capable of reducing the discomforts of morbid preoccupations, jealous thoughts and so on. Certainly what limited information we have on these matters in a clinical context, mainly the results of Rabavilas, Boulougouris and Stefanis (1976), encourages the possibility of generalizing from our experiments. As mentioned earlier, they found no difference between the effects of short and long fantasy presentations. Both of these forms of
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presentation were followed by useful clinical improvements. They also made the incidental observation that significant declines in the untreated obsession are to be expected, hence supporting our interpretations of the results of our experiment as being partly the result of practice effects. Rabavilas et aI. did not investigate the effects of relaxation, but presumably they would have obtained their clinical effects more quickly if they had provided relaxation training prior to presenting the obsessional material.* In reviewing the various experiments reported by Boulougouris and his colleagues, Rachman and Hodgson (1980) point out that it has now been satisfactorily demonstrated that repeated ‘exposures’ to obsessional material are followed by reductions in clinical ratings of discomfort and in reductions of excessive psychophysiological reactions to these stimuli. The possibility of demonstrating similarities between the apparent habituation of subjective discomfort and the habituation of physiological indices is an appealing one. The results reported by Boulougouris and his colleagues support the hope that such similarities will be demonstrated in due course. Plainly, a successful demonstration of this kind would in turn strengthen an interpretation of decremental processes in terms of an habituation model. It should be emphasized that the present findings are concerned solely with the shortterm effects of habituation training, whether it be spaced or massed and regardless of whether or not it is preceeed by relaxation. Before attempting to generalize from these results or to draw conclusions for use in clinical practice, it will of course be necessary to determine the long-term effects of these procedures. The results do, however, point to the desirability of using relaxation in further undertakings of this kind. It should also be remembered that Foa (1979) has demonstrated under different circumstances, with slightly different clinical problems, that habituation can be impeded by depression and/or by the presence of overvalued ideas, To sum up, further research is required in order to confirm the general findings described in this paper, and to determine the long-term effects of habituation training. Further studies of the role of relaxation are worth undertaking,. and clinicians should remain aware of the possible interfering influence of depression and/or overvalued ideas, As far as the newer framework of emotional processing (Rachman, 1980) is concerned, the present results confirm that habituation training procedures, by virtue of their capacity to produce decrements in responsiveness, are likely to provide a useful entry point for studies of the emotional processing of disturbing thoughts. REFERENCES FOA E. (1979) Failures in treating obsessive-compulsives. Eehav. Res. Ther. 17, 169-176. LADERM. and WING L. (1966) Phys~o~ogica~Measures, Sedative Drugs nnd Morbid Anxiety. OUP, London. PARKINSONL. and RACHMANS. (1980, in preparation) A study of unwanted, intrusive thoughts. RABAVILAS A., BOULOUGOURIS J. and SI-EFANISC. (1976) Duration of flooding sessions in treatment of obsessive patients. Behav. Res. Ther. 14, 349-356. RAEAVKASA. and BOUL~UGOURISJ. (1980, in press) Mood changes and flooding outcome in obscssivecompulsive patients. J. nerv. ment Dis. RA~HMAN S. (1971) Obsessional ruminations. Behav. Res. Ther. 9, 229-235. RACHMANS. (1979) An anatomy of obsessions. Behau. Anal. ~~~ &253-278. RACHMANS. (1980) Emotional processing. Behav. Res. Ther. IS, 514. RACHMANS. and DE SILVAP. (1978) Abnormal and normal obsessions. Behav. Res. Ther. 16, 233-248. RACHMANS. and HODGSONR. (1980) Obsessions and Compulsions. Prentice Hall, New Jersey. WOLPE J. (1958) Psychotherapy by Reciprocal Inhibition. Stanford University Press, Stanford.
* This suggestion is strengthens by the latest results from Rabavilas er al. (1980, in press) showing significantly elevated arousal among patients with obsessions.
ARE INTRUSIVE THOUGHTS SUBJECT TO HABITUATION? L. PARKINSONand S. RACHMAN* Department
of Psychology, Institute of Psychiatry, De Crespigny Park, London, SE5 8AF, England (Received 3 March 1980)
Summary-The main question was addressed by studying three groups of non-psychiatric subjects who experienced intrusive and distressing thoughts. The effects of one of three forms of habituation training (massed, spaced and spaced combined with relaxation) on selected thoughts were assessed on a range of measures including latency, duration, discomfort, fading and so on. It appears that intrusive thoughts are subject to habituation. Broad decrements of significant magnitude were observed after each of three forms of habitation training. However, the occurrence of unpredicted decrements attributable to practice effects and to relaxation, presents some problems of interpretation.
INTRODUCTION
Can we get accustomed to our own thoughts? This odd question loses some of its whimsicality when therapists are asked to help relieve the suffering of patients who are tormented by obsessions. These unwanted and unacceptable thoughts are persistent and can produce considerable distress (Rachman, 1979). The sufferer fails to get accustomed to his tormenting thoughts-in contrast to the normal course of events? What is the normal course of events? Do we ordinarily become accustomed to repetitive thoughts, even those which produce distress? From the practical point of view, it is necessary to know whether deliberate attempts to facilitate habituation to distressing thoughts have any chance of succeeding. The main purpose of this investigation was to determine whether selected aspects of intrusive thoughts are indeed subject to decremental processes akin to habituation. The subsidiary aims were to compare the decremental effects of repeated brief formations of the intrusive thought with the effects of a single extended formation (massed vs spaced), and to determine the effects of relaxation training on the decremental process. C’Intrusive thoughts’ refers here to intrusive thoughts or images-see Rachman and Hodgson (1980).] The impetus for the investigation came from a theory proposed to account for obsessions. Rachman (1971) argued the necessity for assuming that everyone has experiences akin to obsessions, and proposed that obsessional material be construed as (largely internal) noxious stimuli to which the person has failed to habituate. Regarded from the more recent prospective implied by the concept of emotional processing (Rachman, 1980) one can reframe the problems of obsessions, and, indeed, of most unwanted and intrusive thoughts, in such a way as to incorporate them in the category of ‘failures of processing’. Either way one is bound to ask whether intrusive thoughts, even up to the level of obsessions, are subject to decremental processes-and if so, which ones? Nor would it be unrealistic to expect the answers to these questions to lead to practical clinical measures. The elaboration of the original theory of obsessions (see Rachman and Hodgson, 1980) and the framework of emotional processing overlap to an extent and share certain features in respect of the present problem of the decremental processes relating to intrusive thoughts. From both starting points one would be led to predict that intrusive * This research was supported by a grant from the Social Science Research Council. B.R.T. 18/5-D
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thoughts are subject to decremental processes, and that habituation training is likely to facilitate such decrements. In view of the tendency of intrusive thoughts to persist (a major source of distress in the case of obsessions) it is useful to consider the conditions that impede or promote the operation of decremental processes. Analyses of these conditions are given in Rachman (1980) and Rachman and Hodgson (1980), and here we need do no more than quote from the original formulation and some of the ensuing predictions. “Broadly speaking, the patient’s inability to habituate to these ruminative stimuli can be overcome by presenting the noxious stimulus in attenuated form under conditions which favour habituation, or by effecting a direct improvement in mood state” (Rachman 1971, p. 234). In the present study we were concerned with the first part of the statement. Making allowances for the important differences in sample characteristicsthe original predictions were made for clinical obsessions, not as in the present study, the unwanted intrusive thoughts of a non-disturbed sample-these selected predictions are partly relevant : Habituation will be facilitated by calm, equable mood states. Mildly disturbing ruminative thoughts will habituate more quickly with short presentations. During the early stages of habituation training, a temporary increase in the disturbance caused by the ruminations may occur. Regular presentation intervals will speed the process of habituation without ensuring endurance. Under calm conditions, long exposures to highly disturbing ruminative thoughts will result in quicker habituation than short exposures. Under calm conditions, long exposures to ruminative thoughts will result in more enduring habituation than short exposures. Although the present investigation has a bearing on only the first three of these predictions, the additional statements are reproduced in order to provide a fuller background to the study. In the present study we sought evidence of habituation-like decrements, and gathered data on the effects of spacing, and of relaxation. It is worth noticing that in an earlier study, preliminary findings on a small sample suggested that ‘normal obsessions’ formed to instruction were of mild intensity (Rachman and de Silva, 1978) and that with repeated practice, their duration and the accompanying discomfort decreased. The latency of the thought formulation increased. It must be emphasized that in the present study we were again concerned solely with short-term decremental processes. Given a clear demonstration of such short-term effects, the subsequent investigation of lasting decrements should present few problems. Although we recorded and analysed 10 characteristics of each intrusive thought, greatest attention was paid to subjective discomfort. This variable was used as the major indicator of decremental change-habituation. As part of the continuing investigation of the nature and structure of unwanted intrusive thoughts (see Rachman and de Silva, 1978, and Parkinson and Rachman, 1980), we took this opportuinity to look into the possibility that intrusive images might respond slightly differently to our repeated formation procedures (habituation training) than do intrusive thoughts. In sum, the major aim of the study was to determine whether unwanted intrusive thoughts (and images) are subject to habituation-like decremental processes. The subsidiary aims were: to compare the effects of massed and spaced trials, to determine the effects of relaxation training on the decremental processes, and to compare the responsiveness of intrusive images and intrusive thoughts. PROCEDURE In keeping with the aims set out in the Introduction, we examined the decremental effects of three forms of habituation training on selected aspects of intrusive thoughts. The three forms of training consisted of: (a) six trials of 2 minutes duration, each separ-
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ated by a 1 minute rest interval, (b) six trials of a similar duration and spacing, but preceded by relaxation instructions, and (c) one extended trial of 12 minutes duration. The effects of each condition were assessed by within and between group comparisons, using the following selection of measures which were administered before and after the completion of each of the relevant forms of training. For each S, two comparably distressing intrusive thoughts or images were chosen (one as the target thought and the other as the non-treated comparison) and then formed to E’s instructions. The time taken by the S to form the selected thought or image to instruction was recorded (latency). The duration of the thought was recorded in seconds. After removing the thought (or image), the S was asked to rate its characteristics on a O-10 scale (10 is the maximum score)degree of discomfort, degree of stressfulness, unacceptability, intensity, controllability, resistance, anxiety, fading, significance, urge to neutralize, competing thoughts, bodily reactions. After completing the relevant type of habituation training each S was once again asked to form the comparison thought/image and the target thought/image. The latency, duration and characteristics of each thought were recorded as before. Subjects were asked to form the comparison or the target thought/image as clearly and vividly as possible and to signal its formation by raising one finger, and to retain the thought until asked to remove it. The loss of the thought, whether intended or not, was signalled by the S lowering his finger. In the case of the two forms of training comprising six 2 minute trials, the Ss were asked to estimate at the end of each trial the amount of discomfort, unacceptability, stressfulness, etc., they had experienced. Trial by trial data were collected. In all cases, a post-trial enquiry was aimed at assessing whether the S had attempted to neutralize the thoughts. The occasions on which the thoughts faded prematurely were recorded. The three forms of habituation training were: (a) spaced practice consisting of six trials of 2 minutes duration separated by rest pauses of 1 minute, (b) spaced practice, as above, preceded by brief relaxation training and (c) one massed practice trial lasting 12 minutes. The control procedure consisted of identical practice-rest sessions but Ss formed neutral thoughts/images of a blank television screen or of an apple. Each S completed a set of experimental trials and a matched set of control condition trials, with the order of presentation balanced in each of the three groups. Subjects
Sixty normal adults, divided into three equal groups, participated in the study. They were included in the study if they were able to describe at least two distressing intrusive thoughts or images, and were willing to devote roughly 1 hr to the training session and complete the brief tests referred to earlier. Once accepted for the study the Ss were randomly allocated to one of the three forms of training procedures.
RESULTS After habituation training decreased responsiveness was observed on almost all of the measures. Most of these results are illustrated in Figs. 1 and 2. Although the overall pattern of decremental changes was remarkably similar with all three forms of habituation training (repeated brief presentations, repeated brief presentations under relaxation, or one extended presentation), some slight differences were observed. So, for example, some of the decreases observed after repeated spaced presentations were of larger magnitude than those observed after the extended or massed presentation. Furthermore, we obtained clear evidence to show that relaxation training expedites most of the decremental changes. Although the final point reached with spaced presentation, with or without relaxation, was no different, the changes were obtained at different speeds. As can be seen from Fig. 3, the subjective discomfort score reduced very rapidly when the subjects were relaxed before carrying out the habituation training. Among those subjects who carried out these repeated practices without prior relaxation, the same degree of reduction in discomfort was achieved, but at a slower rate. This is perhaps the point at which to
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interpolate, especially for the sake of clinicians, that the introduction of relaxation training was followed by surprisingly quick and large reductions in the discomfort and other measures of unpleasantness reported by subjects when they formed their intrusive thoughts to instruction. Whatever the explanation, the results show that habituation training preceded by relaxation brought about immediate and large changes in discomfort. The stressfulness of the thoughts followed a similar pattern (Fig. 4). Thus far, the results appeared to be straightforward and reassuringly predictable. All three forms of habituation training were followed by widespread reductions in discomfort and associated measures of unpleasantness (Tables l-3). These matters are seldom so Table 1. Mean scores, pre- and post-spaced habituation training, plus preand post-scores for control condition Experimental pre-
Control pre-
Experimental post-
Control post-
19.70 48.70 7.70 6.00 7.05 7.85 5.40 2.45 8.20
17.55 52.25 6.85 5.75 6.65 7.40 4.25 3.10 8.25
29.95 45.60 2.55t 4.50t 2.50t 4.80t 2.45* 5.55t 3.70t
24.40 54.80 6.75* 6.75 6.20 6.85 4.20 4.90* 8.05
Latency (sets) Duration (sets) Discomfort Intensity Stressfulness Unacceptability Resistance Controllability Fear/anxiety
*Indicates significant pre-post difference at 5% level. t Indicates significant pre-post difference at 1% level. Table 2. Mean scores, pre- and post-spaced habituation training plus relaxation, and pre- and post-control condition
Latency (sets) Duration (sets) Discomfort Intensity Stressfulness Unacceptability Resistance Controllability Fear/anxiety * Indicates pre-post t Indicates pre-post
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Control pre-
10.80 42.65 7.45 7.00 8.40 9.05 7.30 2.40 7.80
19.70 43.90 7.95 7.10 8.35 9.25 7.35 2.35 7.75
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29.85 2.90t 4.65t 3.551 5.55t 2.15t 6.05t 4.50t
difference significant at 5% level. difference significant at 1% level.
Control post28.05* 39.45 4.90* 5.90t 4.45t 5.70t 4.15’ 4.65* 5.85.
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L. PARKINWNand S. RACHMAN Table 3. Mean scores, pre- and post-massed control condition
Latency (sets) Duration (sets) Discomfort Intensity Stressfulness Unacceptability Resistance Controllability Fear/anxiety
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11.05 49.60 6.65 6.65 6.55 7.70 4.95 3.05 8.10
14.60 46.15 6.85 6.75 6.95 6.70 5.20 3.85 7.65
13.05 51.50 3.251 5.70* 3.20t 3.80t 2sot 6.20t 5.60t
14.45 51.25 6.05 6.25* 5.4s 5.75 4.75 5.10* 7.40
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* Indicates significant difference pre-post at 57; level. t Indicates si~ifi~nt difference pre-post at l”,; level.
straightforward and the major surprise in this part of the experimental results emerged when comparisons were made between the various forms of habituation training and the control condition, which, it will be recalled, consisted of repeated formations of a neutral thought image. Somewhat surprisingly, widespread and fairly large decrements in discomfort, etc., were also observed after the completion of the control condition. Indeed, a number of these decrements were as large as those seen after the most successful of the habituation training conditions. It appears that when relaxation is provided, with or without the addition of the specific habituation training procedures, extensive decrements in discomfort are observed. The use of relaxation came close to swamping the effects of habituation training. In the relaxation plus habituation training condition, however, some of the changes observed after treatment were of greater magnitude than those that took place after the control condition. The four measures on which the addition of the specific training was followed by changes of greater magnitude were discomfort, intensity, resistance and controllability. As far as the effects of the control manipulation are concerned, the clearest ‘practice effects’ were observed on the intensity characteristic (which was seen to decrease significantly after control conditions) and the sense of controllability, which was observed to show a significant increase. The surprisingly broad decrements observed after the control condition can be seen in summary form in Table 4. It is evident that the greatest range of improvements were observed after the control condition in which relaxation was used. However, some significant decrements were also observed after control conditions in which relaxation did not feature. It would appear therefore, that we are dealing with two types of ‘non-specific’ influence-a broad effect of relaxation and a narrow effect that appears to be a consequence of repeated experiences of forming the relevant thoughts to instruction. The extent and magnitude of these control condition changes give the clearest possible notice of how important it is to include control m~ipulations in studies of this kind. In the absence of a control conTable 4. Significant decrements observed after completion of the control condition (pre- to post-) for each of the three groups. The 1% level is shown in the table as 0.01, and ST/,as 0.05 Variables Latency Duration Discomfort Intensity Stress Unacceptability Resistance Controllability Anxiety
Spaced training
Spaced plus relax
Massed training
N.S. N.S. N.S. 0.5 N.S. N.S. N.S. 0.5 N.S.
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N.S. N.S. N.S. 0.05 0.05 N.S. N.S. 0.05 N.S.
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Fig. 5. The latency to thought formation increased gradually during spaced training with relaxation (solid line) and without relaxation (broken line).
dition we would certainly have been led to draw erroneous conclusions about the specificity of the changes that might be expected to follow on the use of habituation training procedures. Turning to the comparisons between intrusive images and intrusive thoughts, it has to be admitted that this part of the investigation was fruitless. No major differences in the decremental processes were observed between thoughts and images. Those few differences which did emerge were of small magnitude and failed to form any meaningful pattern. As far as the parameters of latency and duration are concerned, the prediction that latency would increase with repeated trials was confirmed (see Fig. 5). However, the duration of the thought or image showed no significant alterations over the repeated trials. The subsidiary information about changes taking place during the course of habituation training, was largely disappointing. The occurrence of fading appeared not to be affected by the habituation training. The urge to neutralize was not prominent before the introduction of the training and with one exception, was not stimulated by the training procedure. After habituation training, subjects reported a distinct weakening of .their subjective feelings of bodily reactions, i.e. they reported fewer sensations such as trembling, sweating and so on. Whether these subjective reports of changes in bodily reaction reflected actual decreases in sweating and so on, or whether they were the subjects’ interpretations of some other changes, remains to be seen. The effects of the training procedures were also assessed by comparing the changes observed in the target thoughts, pre- and post-training, with the changes observed in the ‘non-treated comparison thoughts. The differential changes in the ‘treated’ and ‘nontreated’ thoughts were not significant on the measures of fading, neutralizing activities or intrusiveness. However, after ‘treatment’, the target thoughts showed a larger reduction in the associated physiological reactions; the ‘non-treated’ thoughts were similarly accompanied by weakened reactions on. retest, but these decrements were significantly smaller than those observed in association with the ‘treated’ thoughts. In one of the three experimental groups, the significance of the target thoughts to the S was seen to diminish. To summarize the findings so far: widespread and significant decrements in responsiveness were observed after habituation training. These changes were observed regardless of the form of the habituation training. There were, however, differences in the speed with which the changes were induced, and the inclusion of relaxation appeared to expedite matters. In answer to the original question, we can affirm that intrusive thoughts are indeed subject to habituation. However, we immediately have to add that significant decrements in responses of this kind are also observed as a consequence of practice effects, and of relaxation training. So, intrusive thoughts are subject to habituation-but they are also subject to a number of other decremental processes. In therapeutic undertakings, due allowance must be made for the operation of those general influences.
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DISCUSSION The first question to be decided is whether or not the decremental processes observed in the course of this study can safely be regarded as a form of habituation. In the restricted definitional sense, the results certainly appear to be reminiscent of an habituation process-repeated presentations of a’stimulus are followed by declining responsiveness. The awkward problem of deciding whether or not it is reasonable to equate the instructions to form the relevant thought with the type of stimulus that features in conventional habituation studies, is difficult to resolve, If indeed, the verbal instruction given to the subject is regarded as equivalent to, say, the auditory stimulus used in habituation experiments, one has merely to contend with the considerably greater complexity of the verbal stimulus. The problems do not end there, however. In the present study, and in its potential applications, we are after all concerned mainly with the thought that is formed to instruction, rather than with the experimenter’s verbal utterance. Once we leave the relatively colorable position of regarding the experimenter’s verbal instruction as a stimulus, one begins to struggle with the seemingly impossible notion that the thought formed in response to such an instruction provides the stimulus to which the person becomes habituated. Hence, the somewhat whimsical question with which this paper opened- “can we get accustomed to our own thoughts?“. Having acknowledged these considerable conceptual difficulties, we can proceed to regard the decremental processes observed in the experiment as being comparable to habituation. If we do so, the first question is why did relaxation so successfully expedite the observed decremental process? Here we can draw attention to the well-substantiated observation that habituation proceeds more successfully at low rather than high levels of arousal (Lader and Wing, 1963). These authors used the observation that relaxation facilitates habituation as the basis for their re-inte~retation of systematic desensitization in terms of an habituation modei. In essence, they argued that densitization is a form of habituation; moreover, Wolpe’s (1958) use of relaxation to facilitate desensitization does no more than facilitate the process of habituation by lowering the subject’s level of arousal. By the same token the use of preliminary relaxation in the present study facilitated the habituation process by lowering the subject’s arousal. It would seem that attempts to facilitate the decline of disturbing thoughts might we11be facilitated by the use of preliminary relaxation-whether one adopts the perspective put forward by Lader and Wing or not. It should also be pointed out that in the present experiment the preliminary use of relaxation appeared to speed up the process of habituation rather than. change its direction or alter its general course. * The subjects who had spaced repetitions of thought formation, even in the absence of preliminary training in relaxation, showed a gradual decremental change. If we follow the Lader and Wing perspective, the present results appear to fall into place reasonably well. However, they do not easily or satisfactorily account for the almost immediate effects of relaxation. It can be seen in Figs. 3 and 4 that those subjects who had preliminary relaxation showed significant decreases at the end of the first 2 min trial. Although this does not rule out the Lader and Wing explanation, the process does seem to have taken place rather too quickly to fit easily into their account. Without discarding their approach to habituation processes, it might be worthwhile considering the operation of additional processes. Can it be that relaxation makes a contribution over and above that of lowering arousal preparatory to habituation? Indeed, can we go further and suggest that the experimental circumstances and implicit demands made non-specific con~butions to the decremental process. This possibility is strongly supported by the finding that a number of significant decrements were observed even in the case of the ‘untreated’ target thoughts. These findings demonstrate the operation of influences other than habituation training. In a related study (Parkinson and Rachman, in preparation) we have found a relationship between the occurrence of an accompanying physiological reaction and difficulty in * A recent report by Borkovec and Sides (Behau. Ref. Ther. 17, 529-540) shows that relaxation can “maximize imagery vividness, autonomic reactivity to the imagery and decline in reactivity over repeated exposures”.
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removing an unwanted intrusive thought. This finding, considered in conjunction with the results of the present study, suggests that: (a) intrusive thoughts accompanied by physiological reactions are difficult to remove, (b) relaxation reduces physiological reactivity and hence (e) relaxation facilitates the removal of disturbing thoughts. Conversely, training procedures such as thought-stopping or habituation training are not likely to modify disturbing thoughts unless the procedures are combined with relaxation training. In pursuit of this possibility, we are attempting to re-assess the published reports of clinical failures in terms of the use made by relaxing procedures. In addition to the general situational influences already noted, it is necessary to take into account the probably significant effect of simple practice. In order to carry out the experiment, or comparable experimental treatments, it is of course necessary to identify a target thought and a comparable thought which remains untreated. Moreover, it is essential to have at least two repetitions of the formation of each of these thoughts, i.e. the treated target thought and the untreated comparison thought. It seems likely that this simple repetition, carried out for purposes of assessment, is a reactive measure. It follows that in order to demonstrate the particular and additional contribution of any experimental manipulation, one needs to use a procedure that is capable of producing effects of some magnitude. Failure to use a powerful intervention may lead to the production of insignificant results in which the practice effects equal those attributable to the experimental intervention, and hence obscure the process of greatest interest. The surprisingly large decremental influence of non-specific situational factors and of practice effects should be borne in mind when designing experiments of this kind, and in particular, when carrying out evaluative trials of new forms of treatment. A failure to include a comparison thought of equal distress value would certainly undermine the value of any experimental study or treatment evaluation. Turning next to our failure to detect any differences between spaced training and massed training, this result suggests that it is the duration of the thought formation that is relevant rather than the frequency with which the thought is formed. Put into more familiar language, it is the duration of the ‘exposure’ rather than the frequency of exposures that seems to be critical, at least in the short-term. Although the procedures and subjects were somewhat different, the results reported by Rabavilas et at. (1976) are comparable. In their treatment of twelve obsessional-compulsive patients, they were able to find no differences in the effects produced by short vs long fantasy exposures. This is perhaps the point at which to observe that these authors also reported a significant decline in the untreated but comparable obsession-consistent with our evidence of some form of practice effect, perhaps combined with non-specific situational influences. If it can be confirmed that the duration of thought formation plays a major role in influencing the speed and shape of decremental processes, this should provide some clues about the nature of the processes involved. A related possibility is that the amount of decrement observed is a function of the duration of ‘non-threatening’ time during which the thought is held. In other words, if a person holds the distressing thought for a certain minimum period he will learn to tolerate it. The process of habituation is perhaps dependent on a minimum amount of non-threatening ‘exposure’ time. The present findings, if confirmed, may be of clinical significance. They are most relevant to the study and modification of obsessions, but may also tell us something about morbid preoccupations, perhaps even jealousy, and conceivably something about anxious brooding, etc. If we accept that the intrusive thoughts dealt with in the present experiment bear a similarity to obsessions, it means that habituation training techniques are worth exploring (see, for example, Rachman, 1979), and that relaxation is a desirable prerequisite. It might also follow that habituation preceded by relaxation is capable of reducing the discomforts of morbid preoccupations, jealous thoughts and so on. Certainly what limited information we have on these matters in a clinical context, mainly the results of Rabavilas, Boulougouris and Stefanis (1976), encourages the possibility of generalizing from our experiments. As mentioned earlier, they found no difference between the effects of short and long fantasy presentations. Both of these forms of
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presentation were followed by useful clinical improvements. They also made the incidental observation that significant declines in the untreated obsession are to be expected, hence supporting our interpretations of the results of our experiment as being partly the result of practice effects. Rabavilas et aI. did not investigate the effects of relaxation, but presumably they would have obtained their clinical effects more quickly if they had provided relaxation training prior to presenting the obsessional material.* In reviewing the various experiments reported by Boulougouris and his colleagues, Rachman and Hodgson (1980) point out that it has now been satisfactorily demonstrated that repeated ‘exposures’ to obsessional material are followed by reductions in clinical ratings of discomfort and in reductions of excessive psychophysiological reactions to these stimuli. The possibility of demonstrating similarities between the apparent habituation of subjective discomfort and the habituation of physiological indices is an appealing one. The results reported by Boulougouris and his colleagues support the hope that such similarities will be demonstrated in due course. Plainly, a successful demonstration of this kind would in turn strengthen an interpretation of decremental processes in terms of an habituation model. It should be emphasized that the present findings are concerned solely with the shortterm effects of habituation training, whether it be spaced or massed and regardless of whether or not it is preceeed by relaxation. Before attempting to generalize from these results or to draw conclusions for use in clinical practice, it will of course be necessary to determine the long-term effects of these procedures. The results do, however, point to the desirability of using relaxation in further undertakings of this kind. It should also be remembered that Foa (1979) has demonstrated under different circumstances, with slightly different clinical problems, that habituation can be impeded by depression and/or by the presence of overvalued ideas, To sum up, further research is required in order to confirm the general findings described in this paper, and to determine the long-term effects of habituation training. Further studies of the role of relaxation are worth undertaking,. and clinicians should remain aware of the possible interfering influence of depression and/or overvalued ideas, As far as the newer framework of emotional processing (Rachman, 1980) is concerned, the present results confirm that habituation training procedures, by virtue of their capacity to produce decrements in responsiveness, are likely to provide a useful entry point for studies of the emotional processing of disturbing thoughts. REFERENCES FOA E. (1979) Failures in treating obsessive-compulsives. Eehav. Res. Ther. 17, 169-176. LADERM. and WING L. (1966) Phys~o~ogica~Measures, Sedative Drugs nnd Morbid Anxiety. OUP, London. PARKINSONL. and RACHMANS. (1980, in preparation) A study of unwanted, intrusive thoughts. RABAVILAS A., BOULOUGOURIS J. and SI-EFANISC. (1976) Duration of flooding sessions in treatment of obsessive patients. Behav. Res. Ther. 14, 349-356. RAEAVKASA. and BOUL~UGOURISJ. (1980, in press) Mood changes and flooding outcome in obscssivecompulsive patients. J. nerv. ment Dis. RA~HMAN S. (1971) Obsessional ruminations. Behav. Res. Ther. 9, 229-235. RACHMANS. (1979) An anatomy of obsessions. Behau. Anal. ~~~ &253-278. RACHMANS. (1980) Emotional processing. Behav. Res. Ther. IS, 514. RACHMANS. and DE SILVAP. (1978) Abnormal and normal obsessions. Behav. Res. Ther. 16, 233-248. RACHMANS. and HODGSONR. (1980) Obsessions and Compulsions. Prentice Hall, New Jersey. WOLPE J. (1958) Psychotherapy by Reciprocal Inhibition. Stanford University Press, Stanford.
* This suggestion is strengthens by the latest results from Rabavilas er al. (1980, in press) showing significantly elevated arousal among patients with obsessions.