Psychiatry Interpersonal and Biological Processes

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Making Sense of Delusions Philippa A. Garety To cite this article: Philippa A. Garety (1992) Making Sense of Delusions, Psychiatry, 55:3, 282-291, DOI: 10.1080/00332747.1992.11024602 To link to this article: http://dx.doi.org/10.1080/00332747.1992.11024602

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Making Sense of Delusions Philippa A. Garety TRUE delusions have been conventionally regarded as primary or psychologically irreducible (Jaspers 1913/1959) and thus only explicable in organic terms. While Jaspers acknowledged the existence of secondary delusions, which may be understood in the light of related affect, other experiences, or hallucinations, these were of lesser theoretical importance than true delusions, in which he found a change in "the totality of understandable connections." AngloAmerican psychiatry, in espousing Jaspers and rejecting psychoanalysis, has in consequence concentrated on the form and not the sense of delusions. In the past two decades, however, during which the edifice of a clear discontinuity between madness and sanity has been crumbling (Bentall 1990; Strauss 1969), the idea of (all) delusions as attempts to construct sense out of disordered experience has been emerging (Garety et al. 1991; Maher 1974,1988). One of the interesting questions to arise in this debate is whether delusions are normal (conscious) accounts of abnormal experience (such as hallucinations), as Maher has argued, or whether the accounts themselves derive from any (preconscious) abnormalities, such as reasoning biases, as Garety et al. have proposed, for some delusions. The literature on the psychology of reasoning is relevant to this question. Cognitive psychologists and philosophers of science argue that the accumulation of knowledge, whether personal beliefs or scientific facts, is not a passive process of describing experience, but rather is theory driven. Furthermore, people seek in general to confirm their ideas, not to disprove them (e.g., Kahneman et al. 1982; Kuhn, 1962; Lakatos 1970). Once a belief is strongly held, new information will be

less effective in changing the theory than that same information would be if the prior belief were weakly held (Alloy and Tabachnik 1984). Thus to be incorrigible, as deluded people are said to be, is not in itself abnormal, although incorrigibility can presumably be a matter of degree. In terms of belief maintenance, therefore, these theories seem consistent with Maher's views, in that the way that these strong beliefs (delusions) are maintained may not be abnormal. Maher's views are perhaps less convincing in terms of the formation of delusions. Prior expectations and knowledge play a role in the formation of new beliefs: If some new information is at odds with wellestablished knowledge about the world, such information will be rejected in favor of maintaining a stable belief system (Quine 1953). However, as Chapman and Chapman (1988) have commented, delusional patients sometimes deny wellestablished facts of physical reality that they and others have experienced all their lives, appearing to focus instead on prominent current stimuli. While it is therefore normal for people to construct their ac-

Philippa A. Garety, PhD, is Lecturer in Psychology and Chartered Clinical Psychologist, Department of Psychology, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK.

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counts of the world, the process of the construction of some of these delusional beliefs may involve abnormalities. In this paper, detailed investigations of one deluded subject are described, in the hope that a more fine-grained analysis than the format of group studies usually permits, will cast some light on these questions. THE CASE OF THE GOOD AND BAD AEROPLANES

The Problem Brendan Bryan (a pseudonym) was referred by his psychiatrist because although his "schizoaffective illness is as well controlled by medication as ever before, he remains bothered by aeroplanes who 'attack' him." At the first interview, Mr. Bryan reported that aeroplanes and helicopters were following him around, and, using their sophisticated instrumentation, were reading his mind and experimenting upon him. At times he feared they would kill him, but he realized that if they had wanted to, they could have done this long before. Mr. Bryan offered no thoughts as to who might be in the planes. (Indeed, he seemed to anthropomorphize the planes themselves.) In the previous week, Mr. Bryan had felt suicidal about the planes and had telephoned the Samaritans (an emergency telephone counseling service) for advice. He had also recently stopped a police officer in the street to complain and had been to a Citizens' Advice Bureau to ask if legal action could be taken against the planes. He recognized that no one believed him. History of the Problem Responding to a structured interview to assess the initial formation of the belief, and the factors currently maintaining it, Mr. Bryan related that the belief gradually formed in his mind at the time that

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he had his first "breakdown" 8 years before. At that time, he recalled that his mood and thinking were both disrupted in that he felt quite elated but also confused, and shortly after he started to notice planes that appeared to be following him. For some years, he thought that he was simply under surveillance, but 3 years before the interview - at the time of the breakup of his marriage, when he had another "breakdown" - he became convinced that the planes were directly interfering with his thoughts by putting thoughts into his mind and, possibly, controlling his movements. He appears to have reported the symptoms of thought insertion and thought broadcasting at that time. Mr. Bryan reported that over the years he would test out his beliefs. He would go out and look in the sky to see if there were any planes that seemed to be following him. This activity resulted in daily confirmation of his belief: Whenever he went out, planes could be seen in the sky, and on occasion they would signal to him by turning suddenly to show him their airline insignia and numbers. Personal and Psychiatric History Brendan, now aged 34, was born in India of Christian parents. He has two younger brothers and a third who is his twin. They had a strict religious upbringing and attended a church school, where English was the language of study. Brendan's twin had a "breakdown" at the age of 14 and was last known to be unemployed and wandering round France. One brother remained in India, where he looks after his parents, and the youngest, who is married, lives near Brendan in London and works in an office. Brendan was an average student at school and came alone to England at the age of 21 to train as an occupational therapist. He found the studies very difficult and eventually, after failing his exams and being admitted to hospital, was accepted to work at a lower level as a practi-

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cal therapist (or therapy aide). During this period, he had an arranged marriage to a woman in India, who was not informed of his psychiatric problems. His wife left him 3 years before our sessions, after 4 years of marriage. There were no children. Brendan worked for 5 years as a practical therapist, during which time he had approximately annual admissions to hospital. Finally he was retired from work on medical grounds. At the time of our sessions, he was attending a psychiatric day center and working as a volunteer in a charity shop. Brendan was first admitted to a psychiatric hospital while studying for his final exams, which he had already failed once before. He became overactive and sleepless, and believed he had special powers from the Holy Spirit. He noticed aeroplanes following him and felt confused in his thinking. At times he felt very sad. Brendan had six further psychiatric admissions, occurring approximately annually, and was diagnosed as suffering from a schlzoaffective psychosis. Two admissions followed serious suicide attempts. At the time of our sessions, Brendan had remained out of hospital for 1 year and was anxious to establish a pattern of life that would protect him from frequent relapses. Although distressed by the worry about the aeroplanes, he recognized that there were periods when his state was worse, when he, in his own terms was "ill": These times were characterized by beliefs about having extraordinary powers from the Holy Spirit. Assessment of the Belief

At the first interview, Brendan said that he was absolutely certain that the planes were following him, and that this belief was not a symptom of his illness (in the way that, for instance, he recognized that his past belief about the Holy Spirit was a symptom). He had been extremely preoccupied over the past week about the planes, and as already reported, was very distressed. The distress took the form of fear: Brendan reported being "terrified" of

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the planes and of what they were doing to his mind. The evidence Brendan cited to support his belief was the daily presence of aeroplanes in the sky; he no longer felt compelled even to look out for and note down the type of planes as once he had. He could not think of any recent or past events that would contradict his belief. To further assess the way Brendan dealt with evidence (see Brett-Jones et al. 1987), he was asked what he would think if, in a given week, we both noted down the planes we saw and if it transpired that there was no difference in how many planes we detected. At first Brendan said that this would cause him to doubt that the planes were following him in particular, but then he rapidly added that he would wonder if the planes had found out that this was being done and so changed their habits. An answer of this sort, where the contradictory evidence is accommodated within the existing delusional belief and is not genuinely evaluated, has been found to be associated with a poor response to therapy (Chadwick and Lowe 1990; Brett-Jones et al. 1987). When responding to this question, Brendan also made a revealing comment. He said that he is very attached to the planes and would miss them if they suddenly left his life. Some of them seemed to him to be benevolent, and his life would be even more lonely without them. Mr. Bryan was asked to record for 1 week, on a three times a day monitoring form, whether he believed at that moment that the planes were influencing him; and, on a 5-point scale, both how frightened he felt and how preoccupied he had been in the past 5 minutes. On each of the 21 data points, Brendan believed that the planes were influencing him. However, the levels of distress and preoccupation were variable. His fear varied from 0 (no fear) to 3 (very frightened); and preoccupation, from 1 to 3. For one whole day, Brendan was not at all frightened: He had been on a day trip with his day center to a rural, stately home. He explained this both by the presence of fewer aeroplanes and as a

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result of the reassuring company of friends. On the other days, he was less frightened and preoccupied in the evenings than in the mornings and at lunchtime. At this stage in the assessment, it was noted that although Mr. Bryan believed the planes were reading his mind, he did not report experiencing any identifiable changes in his thinking or movements on or after observing the planes. Sufficient evidence was the presence of the planes and their changes of direction, accompanied by noise. Two further investigations were conducted. Firstly, Mr. Bryan was asked to undertake a probabilistic reasoning task, to detect biases in reasoning. This task and data relating to deluded subjects' responses are described in full in Garety et al. (1991). Briefly, subjects are asked to make judgments about which of two jars, once withdrawn from view, is the source of beads shown to them, on the basis of the color of the beads; subjects know the proportions of colored beads in each jar. The task is easy and generates few errors. The interest in the task is in how the subject undertakes it: Does s/he jump to conclusions or exercise excessive caution? Is the subject over- or underconfident in his/ her judgment? Once a decision is made, is the subject reluctant or willing to change his/her mind, if the evidence points the other way? Mr. Bryan's responses were interesting. In the first condition, in which subjects are invited to make a decision on the basis of as many items of information as they need, he showed the bias present in a proportion of deluded subjects of jumping to conclusions: he decided on the basis of only one item of information. (Controls generally take between three and five items.) In the second condition, in which subjects make repeated estimates of the probability of one jar having been chosen, as they are shown each of a predetermined number and sequence of beads, Brendan appeared to be excessively influenced by the current stimulus. As each

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bead of a different color was chosen, he changed his estimate to favor the jar with most beads of that color, not making use of the information accumulating from the sequence of previous draws. Thus he did not stick to one hypothesis rigidly; rather he showed an opposite tendency to change his mind as soon as potentially disconfirmatory evidence was presented. Finally, Brendan completed a simple test of verbal intelligence, the Mill Hill Vocabulary Test. Despite having been educated in English and, with difficulty, having studied for some years, his score was well below average, at about the 10th percentile for men of his age. Formulation Mr. Bryan's belief that aeroplanes are influencing him developed over some years. It started at the time of his first psychotic episode and changed in content as he had further episodes. He appears to have experienced the symptoms of thought broadcasting and insertion, at one stage. By then, Mr. Bryan already believed that the planes were interested in him. What were the respective roles of prior expectation, mood, abnormal experience, and reasoning in the formation of this belief? A simple explanation of the Maher school would suggest that Mr. Bryan had abnormal experiences in terms of a change in his thinking, resulting in a sense of puzzlement, and found an explanation for this change in a belief about the action of the aeroplanes. But, while simple, this account leaves some factors unexplained. Why did aeroplanes, which presumably did not show substantially altered patterns of activity, seem to Mr. Bryan to serve as an explanation of his problems? How did Mr. Bryan's mood influence him? Why did he accept such a fantastical explanation for his experiences? Why did he apparently require so little evidence? The different factors postulated as involved in the construction of Mr. Bryan's belief are represented in Figure 1. Here a

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, 1

PRIOR EXPECTATIONS

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PHILIPPA A. GARETY

3

CURRENT INFORMATION

INFORMATION PROCESSING STYLE

Stage 1

Stage 1 - prior learning, mood and personality - recent experience of exam failure ~ attempt to distract self from distressing cognitions.- hypomania - paranoid expectations & attributions enhanced by experiences as an immigrant

----------------------

~ Stage 2

- planes are following me - bad things are happening to me (divorce) "'Iow mood - . . negative expectations - continuing paranoid expectations?

- aeroplanes in sky disengaged from perceptual context

~

OR

~

- intrusion into consciousness of stimuli (aeroplanes) not usually noticed?

.-

- rapid decision making - periodic failure of central monitor of willed intentions?

-----------------------Stage 2 - areoplanes always in sky, somtimes turning noisily

- cognitively simple reasoning - excessive focussing on current stimuli and failure to make use of past learned regularities - low verbal 10

4

+

SEARCH FOR

1. PLANES ARE FOLLOWING ME

,

EVIDENCE

2. PLANES ARE INFLUENCING ME

5

,

(confirmatory)

BELIEF

- confused thinking or - thought interference?

1

REINFORCEMENT - anxiety reduction - defence against depressive cognitions

I Figure 1. A model of the factors involved in the formation and maintenance/change of B.B.'s beliefs.

model of normal belief formation is assumed in which prior expectations interact with current experience and style of reasoning to result in a judgment (belief). This belief is then changed or maintained as a result of its reinforcing consequences, its impact on prior expectations, and the further information that the subject encounters or seeks out. This model is based on the work of Kahneman et al. (1982), Fischhoff and Beyth-Marom (1983), and Alloy and Tabachnik (1984), and is described more fully in Garety (1991). Mr. Bryan's belief changed over time: The model considers the factors at stage 1, when the first belief was formed, and at stage 2, when it changed from the belief that he was being followed by the planes to believing that he was being influenced. In box 1, stage 1, Mr. Bryan's state before forming his belief is represented. As for any individual, he would start with a

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set of preexisting expectations, mood states, and his unique personality. Recent experiences, such as being an immigrant and failing his examinations, would have further influenced his mood and expectations. It seems likely that in Mr. Bryan's case, mood is very important. He had his first breakdown at the time of personal failure and first presented with symptoms of hypomania. Neale (1988) has speculated on the defensive functions of manic episodes and on the cognitive mechanisms by which grandiose delusions may result (such as the use of pleasant fantasies to distract from harsh reality, which, under certain circumstances, become difficult to distinguish from reality). At the beginning, Mr. Bryan's central delusion concerned having special powers from the Holy Spirit, and the belief about aeroplanes following him had an element of his being a special focus of attention. This possibly dis-

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tracted him from the distress of exam failure. Cross-cultural factors may also be relevant. Westermeyer (1988) argues that both the structure and content of most delusions are not culture bound and that delusions can be readily identified across cultural boundaries. However, he notes that cultural change fosters paranoid delusions, in that, unsurprisingly, immigrants and refugees show high levels of paranoid ideation. It is therefore possible that Mr. Bryan's recent experiences as an immigrant had engendered paranoid expectations and attributions. Recent research (Kaney and Bental11989) has also demonstrated that subjects with paranoid delusions show a characteristic attributional style, in which they make excessive external attributions for negative events. The expectations influence the selection of information in the environment that is detected (box 2). The principal evidence cited by Mr. Bryan, at stage 1, was the flying of aeroplanes overhead. It is not clear whether the perception of this was in any way abnormal. Were there perceptual changes at the time of his first episode, which caused the elements of the visual field to become separated from their context, so that aeroplanes, experienced as unexpected, became especially salient, in the way that Matussek (19521 1988) proposed? Frith (1979) has also suggested that in schizophrenia, percepts that would normally be ignored arrive abnormally in consciousness and therefore demand an explanation. Possibly some such abnormality occurred when Mr. Bryan first noticed the aeroplanes. In addition to the role of prior expectations, mood, and abnormal experience, there is evidence that Mr. Bryan's reasoning showed characteristic biases (box 3). Mr. Bryan offered no explanation of how the planes influenced him: He seemed to require no account of the physical mechanism that was operating, ignoring the ordinary physical realities that he otherwise accepted. This is behavior of the type that Chapman and Chapman (1988) noted, in

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which the delusional person demonstrates a loss of the benefit of accumulated life experience, accounting for a failure to reject delusional beliefs as unrealistic. Here the reasoning is not entirely normal but, rather, excessively cognitively simple (Radley 1974) and fails to make use of past learned regularities (Garety 1991; Hemsley 1990). In addition to his uncritical acceptance of the extraordinary behavior of the planes, there are also other indications of impoverished or biased reasoning. His assessed intellectual (verbal) functioning was low, and his reasoning on the probabilistic task was biased toward a rapid "jump to conclusions" style and an overemphasis on current stimuli. This reasoning style would further facilitate the formation of hypotheses on the basis of little information and would render more likely the ignoring of past learning. Belief maintenance would also be affected by these biases. The interacting combination of expectation (including mood), information, and the processing of that information leads to Mr. Bryan's belief: his attempt to make sense of experience (box 4). It is plausible, as Maher (1988) suggests, that this arrival at an explanation, reducing anxietyprovoking uncertainty, is reinforcing (box 5). In this case also, the notion of being a special focus of attention (at stage 1) may have helped to bolster Mr. Bryan's flagging self-esteem in the face of failure and might defend against depression (Neale 1988). Mr. Bryan reported that in the early stages he sought confirmation of his belief: He looked out for aeroplanes. This confirmatory activity is not itself abnormal: The confirmation bias is well known in normals (Kahneman et al. 1982). However, in this case, where a reasoning bias appeared to foster belief formation, it is also likely to enhance belief maintenance on scant evidence. However, the belief was not stable. We know that Mr. Bryan's mood deteriorated, the "manic defense" possibly breaking down under the weight of repeated negative experiences including the major one of his divorce (box 1). In a depressed

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state, negative expectations of the world and the future are common. Mr. Bryan may also have continued to hold paranoid expectations. In this state, at stage 2, he encountered and selectively attended to the environment (box 2). He detected aeroplanes always in the sky, often turning suddenly, apparently signaling to him. His thinking was also experienced as subject to interference. Frith (1987) proposes that symptoms of thought interference are a consequence of a failure in the system whereby we monitor our intended actions. If thoughts occur in the absence of this central monitoring, they might be attributed to alien forces. This monitoring permits the distinction between internally generated (willed) and externally generated (stimulus-elicited) actions. How does this fit with Mr. Bryan's symptoms of thought insertion and broadcasting? If the belief about aeroplanes following him had come after the report of the symptoms, the belief might be thought to explain them; however, these symptoms apparently occurred after the initial belief formation. They may in fact have partially resulted from the earlier delusional belief, rather than vice versa. Belief can drive perception and experience (Slade and Bentall 1988). Thus, when already believing that he was the special focus of attention of the aeroplanes and experiencing a further distressing life event (e.g., the end of his marriage), with a resultant lowering of mood and lack of clarity or "confusion" in his thinking, Mr. Bryan may have speculated on what role the planes were playing in this. Believing that the planes were doing bad things to him and feeling confused may in turn have led to an experience of interference with his thinking (rather than simply confusion) enhanced by a failure of the central monitor of willed intentions. In this way, prior expectations, abnormal experience, and a cognitive failure may have converged, resulting in the final, more stable belief that the planes are influencing his mind.

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Intervention Mr. Bryan was seen for a further 10 sessions and attempts were made to intervene to reduce conviction in and distress about his belief. The intervention was planned at two levels. Firstly, an attempt was to be made to reduce conviction by providing an alternative explanation of Mr. Bryan's experiences, drawing on the ideas in the formulation although somewhat simplified. It was proposed to Mr. Bryan that his beliefs arose at the times of his "breakdowns" and that they represented his attempts to make sense of the frightening experiences he was having and to help temporarily to ward off depression. It was also suggested that his style of reasoning led to forming judgments quickly. Despite no longer having these experiences, the belief remained because it had been important to him in making sense of what had happened and even in the present continued sometimes to afford an explanation for some of his problems. The second intervention was directed at Mr. Bryan's mood disturbance and his feelings of isolation and failure. It was noted that he was more vulnerable to preoccupation and distress about the belief when alone and depressed. Mr. Bryan's thoughts and feelings about himself and the future were explored, and he was encouraged to engage in more moodenhancing activities and to increase his social contacts. Measures suitable for repeated testing of belief conviction and associated distress were employed (Brett-Jones et al. 1987; Garety, 1985). "Personal questionnaire" measures treat delusions as multidimensional and are reliable and sensitive to small changes. These were used in the sessions and were supplemented with self-ratings of conviction and distress between sessions. Mr. Bryan's recording between sessions was not consistent: He often reported that he was too frightened to make recordings because the planes were in some way keeping an eye on him. The strategy of providing an altern a-

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MAKING SENSE OF DELUSIONS Conviction scores Certain

5 ,..---------------------------...,

Almost certain

4

Probable

3

Possible

2

Unlikely

Certain that not

0

LL_ _ _L -_ _~---..l-----'----'------.J'---------LJ

2

3

4

5

6

7

8

Sessions (May-Oct) Figure 2. B.B.'s belief conviction that "the planes are influencing me," as assessed by personal questionnaire, in sessions.

tive explanation for his belief proved moderately successful, within the sessions, at reducing Mr. Bryan's belief conviction (see Figure 2). On the session before this alternative was presented, his conviction assessed by the personal questionnaire was 4/5 (almost certain). On subsequent sessions, after further discussions, his score decreased at first dramatically to 1/5 and then 0/5 (certainly not true), and then stabilized back at 2/5 (just possible). However, between sessions, conviction always reverted, by Mr. Bryan's self-rating, to absolute certainty. He reported that invariably, when alone and observing the planes, he would again become certain that they were influencing him. A similar pattern applied to the measure of distress, which was always lower within sessions. Between sessions he remained occasionally suicidal, although over the weeks there was gradual improvement. Why did the reduction in conviction fail to generalize from the therapy session to other times? Firstly, Mr. Bryan's performance on the previously described reasoning task offers a partial explanation.

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It was clear from it that he was strongly influenced by the stimuli that are immediately present in the environment, and that he was excessively quick to change his hypothesis when presented with stimuli that may point to an alternative. Thus, within sessions-discussing his fears in a safe environment - his anxiety was for the present allayed and he was able to consider the alternative hypothesis. When alone, however, and presented with the powerful stimulus of the plane, he rapidly shifted to his prior hypothesis. An attempt was made to counteract this by writing out a card, on which the arguments were summarized, for him to read when alone and bothered by the planes. This was not successful since Brendan reported that at the time he would always feel too frightened to be able to take in the arguments. A second reason, which became more apparent as time progressed, was Brendan's ambivalence about the planes. Although sometimes he said the planes made him feel suicidal; at others, they made him feel important. When away on holiday, where there were fewer planes, he

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missed them. It seems that the original "manic defense" function still held partial sway. Finally, it was found - and this is consistent with his low Mill Hill Vocabulary Score - that Mr. Bryan had some difficulty engaging in sustained discussion and in considering alternative hypotheses; nor was he good at relating evidence to hypotheses. His current intellectual functioning did not equip him well for these tasks. The second therapeutic approach, of alleviating distress and increasing moodenhancing activities, was more successful. Worries about the future in particular were addressed, and the effects on selfesteem of being unemployed. Mr. Bryan enrolled in a work-retraining scheme and greatly increased his leisure activities. He went on holiday twice. He expressed a renewed sense of hope for the future. By the end of the sessions, Mr. Bryan reported that the distress experienced on account of the planes had decreased, and by the last appointment frequency of thinking about the planes was considerably re-

duced. Here, therefore, one pattern of recovery from a delusion occurred, where there is a reduction in distress and preoccupation, but no consistent change in conviction, a pattern that has been noted by other workers (Brett-Jones et al. 1987; Hole et al. 1979). Conclusions In this paper one man's delusional belief has been conceptualized as resulting from a variety of interacting disturbances: affective, experiential, and judgmental. Delusions are seen as complex phenomena, which benefit from a detailed multifactorial assessment of the individual case. The delusion described here is seen as the final outcome of the subject's disordered attempt to make sense of his abnormal experiences and disturbed mood. In this case both experience and reasoning are found to be biased, and attempts to understand the delusion need to take account of both (interacting) sources of bias if intervention is to be optimally successful.

REFERENCES ALLOY, L. B., and TABACHNIK, N. Assessment of covariation by humans and animals: The joint influence of prior expectations and current situational information. Psychological Review (1984) 91:112-49. BENTALL, R. P. Reconstructing Schizophrenia. Routledge, 1990. BRETT-JONES, J., GARETY, P. A., and HEMSLEY, D. Measuring delusional experiences: A method and its application. British Journal of Clinical Psychology (1987) 26:257-65. CHADWICK, P., and LOWE, F. The modification of delusional beliefs. Journal of Consulting and Clinical Psychology (1990) 58:225-32. CHAPMAN, L. J., and CHAPMAN, J. P. The genesis of delusions. In T. F. Oltmanns and B. A. Maher, eds., Delusional Beliefs. Wiley, 1988. FISCH HOFF, B., and BEYTH-MAROM, R. Hypothesis evaluation from a Bayesian perspective. Psychological Review (1983) 90:239-60. FRITH, C. D. Consciousness, information processing and schizophrenia. British Journal of Psychiatry (1979) 134:225-35. FRITH, C. D. The positive and negative symptoms of schizophrenia reflect impairments in the per-

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ception and initiation of action. Psychological Medicine (1987) 17:631-48. GARETY, P. A. Delusions: Problems in definition and measurement. British Journal of Medical Psychology (1985) 58:25-34. GARETY, P. A. Reasoning and delusions. British Journal of Psychiatry (1991) 159(suppl. 14):14-18. GARETY, P. A., HEMSLEY, D. R., and WESSELY, S. Reasoning in deluded schizophrenic and paranoid subjects: Biases in performance on a probabilistic inference task. Journal of Nervous and Mental Disease (1991) 179:194-201. HEMSLEY, D. R. What have cognitive deficits to do with schizophrenia. In H. Huber and G. Gross, eds., Weissenauer Schizophrenia Symposium No. B. Schatauer-Verlag, 1990. HOLE, R. W., RUSH, A. J., and BECK, A. T. A cognitive investigation of schizophrenic delusions. Psychiatry (1979) 42:312-19. JASPERS, K. General Psychopathology, 1913. Translated by M. W. Hamilton and J. Hoenig. Manchester University Press, 1959. KAHNEMAN, D., SLOVIC, P., and TvERSKY, A.Judgment under Uncertainty: Heuristics and Biases. Cambridge University Press, 1982.

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MAKING SENSE OF DELUSIONS KANEY, S., and BENTALL, R. Persecutory delusions and attributional style. British Journal of Medical Psychology (1989) 62:191-98. KUHN, T. S. The Structure of Scientific Revolutions. University of Chicago Press, 1962. LAKATOS, I. Falsification and the methodology of scientific research programmes. In I. Laktos and A. Musgrave, eds., Criticism and the Growth of Knowledge. Cambridge University Press, 1970. MAHER, B. A. Delusional thinking and perceptual disorder. Journal of Individual Psychology (1974) 30:98-113. MAHER, B. A. Anomalous experiences and delusional thinking: The logic of explanations. In T. F. Oltmanns and B. A. Maher, eds., Delusional Beliefs. Wiley, 1988. MATUSSEK, P. Studies in delusional perception. In The Clinical Roots of the Schizophrenia Concept, 1952. Translated by J. Cutting and M. Shepherd, eds. Cambridge University Press, 1988.

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NEALE, J. M. Defensive functions of manic episodes. In T. F. Oltmanns and B. A. Maher, eds., Delusional Beliefs. Wiley, 1988. QUINE, W. V. O. Two dogmas of empiricism. In From a Logical Point of View. Harvard University Press, 1953. RADLEY, A. R. Schizophrenic thought disorder and the nature of personal constructs. British Journal of Social and Clinical Psychology (1974) 13: 315-27. SLADE, P. D., and BENTALL, R. P. Sensory Deception: A Scientific Analysis of Hallucinations. Croom Helm, 1988. STRAUSS, J. S. Hallucinations and delusions as points on continua function. Archives of General Psychiatry (1969) 20:581-86. WESTERMEYER, J. Some cross-cultural aspects of delusions. In T. F. Oltmanns and B. A. Maher, eds., Delusional Beliefs. Wiley, 1988.

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Making sense of delusions.

True delusions have been conventionally regarded as primary or psychologically irreducible (Jaspers 1913/1959) and thus only explicable in organic ter...
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