Behavioral Residential Treatment, Vol. 6, No. 5, 355-366 (1991)

ASSESSMENT OF DELUSIONAL BELIEFS DURING THE M 0 D I FI CATION 0 F D E i LUSlO N AL VE R BALl ZATlO NS

Will Himadi Florida State Hospital, Unit 15, Chattahoochee, Florida 32324, USA

and Frances Osteen, Andrew J. Kaiser and Kimberly Daniel Florida State University

This study examined the strength of delusional beliefs during the modification of delusional verbalizations of a 5 1 year-old chronically mentally ill inpatient. The changing-criterion design was used to document the effectiveness of a behavioral treatment package to alter the rate of delusional responses to personal background questions. The results revealed a stepwise decline in the frequency of delusional responses. Generalization effects to novel interviewers were obtained. No changes were obtained on the subject’s ratings of delusional beliefs, with the subject assigning ratings of absolute conviction to his beliefs throughout the duration of the study.

The major components to the definition of a delusion include a false personal belief or idea that is not shared by other members of the individual’s culture and that is impervious to contradictory facts or counter-arguments (cf. APA, 1987; Garety & Hemsley, 1987; Haynes, 1986; Maher & Ross, 1984; Winters & Neale, 1983). Delusions are a prominent feature of a variety of psychiatric disorders including mood and delusional disorders and the schizophrenias. For example, the International Pilot Study of Schizophrenia (IPSS, WHO, 1973) found that the prevalence of delusions among schizophrenics was high. Further- more, delusional verbalizations are the most frequent behaviors leading to psy- chiatric readmission for schizophrenics (Liberman, Teigen, Patterson & Baker, 1973; Varni, Russo & Cataldo, 19’78).

Behavioral approaches for the modification of delusional verbalizations have approximately a 30-year history. The following procedures have been used: differential social reinforcement (Ayllon & Haughton, 1964; Ayllon & Michael, 1959; Bulow, Oei & Pinkey, 1979; Kennedy, 1964; Liberman et af., 1973; Rick- ard, Dignam & Horner, 1960; Varni et af., 1978), feedback and token reinforce- ment (Patterson & Tiegen, 1973; Wincze, Leitenberg & Agras, 1972), timeout (Cayner & Kiland, 1974; Davis, Wallace, Liberman & Finch, 1976; Sanders,

Address correspondence and reprint requests to Dr. Bill Himadi, as above.

0084558 1/91/050355-12$06.00 0 1991 by John Wiley & Sons, Ltd

356 B. Himadi et al.

1971), satiation (Wolff, 1971), and behavioral treatment packages with multiple components (Alford, Fleece & Rothblum, 1982; Burgio, Brown & Tice, 1985; Foxx, McMorrow, Davis & Bittle, 1988; Nydegger, 1972; Schraa, Lautmann, Luzi & Screven, 1978). While positive results were reported for the modification of delusional verbalizations, the changes were generally obtained under circums- cribed conditions with no or limited generalization effects (cf. Alford et al., 1982; Davis et al., 1976; Foxx et al., 1988; Liberman et al., 1973; Patterson & Tiegen, 1973; Wincze, Leitenberg & Agras, 1972). For instance, Patterson and Teigen (1973) used instructions and token reinforcement to produce factual answers to personal background questions of a 60 year-old female hospitalized schizophrenic. A multiple-baseline design across responses was used with the treatment contingency applied sequentially and cumulatively across five per- sonal background questions. A treatment effect was obtained but two generaliza- tion interviews in a postdischarge environment conducted by mental health aftercare workers produced disappointing results.

Alford (1986) contended that behavioral treatment of delusional verbaliza- tions does not guarantee reductions in delusional beliefs. While recent behavioral treatment studies have targeted delusional cognitions for change (e.g., Alford, 1986; Chadwick & Lowe, 1990; Johnson, Ross & Mastria, 1977; Lowe & Chad- wick, 1990; Milton, Patwa & Hafner, 1978), the status of delusional cognitions during the modification of delusional verbalizations has not been examined. The purpose of the present study was to examine the strength of delusional beliefs during the modification of delusional verbalizations of a 5 1 year-old chronically mentally ill inpatient.

METHOD Subject

The subject was a 51 year-old, white male with a diagnosis of Schizophrenia, Chronic Undifferentiated Type (DSM 111-R 295.92, American Psychiatric Association, 1987). He had been continuously hospitalized at a state psychiatric facility since 1971. At the beginning of the study, the subject was receiving 60mg per day of thiothixene [navane]. There were several medication changes during the course of the study. During the week of session two, the subject’s thiothixene [navane] was discontinued, and he was started on fluphenazine hydrochloride [prouxin] (10mg/day). His medication was increased to 15 mg/day on the day of session four and finally increased to 20mg/day on the day prior to session nine. There were no further medication changes during the remainder of the study.

Delusions 357

The subject completed 2 years of formal education, and intelligence testing conducted approximately 1 month prior to the start of this study revealed the following Wechsler Adult Intelligence Scale-Revised scores: Verbal, 70; Per- formance, 68; Full Scale, 68. This places the subject in the mentally retarded range of intellectual functioning. Data from the Time Sample Behavioral Check- list (TSBC) (Licht, 1984; Paul, 1987), a direct observational coding system that allows for the concurrent monitoring of multiple facets of behavior, revealed that the subject exhibited more inappropriate behavior during a 1 month period immediately prior to the start of the study than 50% of a sample of individuals in public mental institutions (Paul & Mariotto, 1987).

Setting The study was conducted in a 50-bed unit designed for the rehabilitation

of the chronically mentally ill. The unit incorporates a social learning treatment program modeled after the innovative program described by Paul and Lentz (1977). The program includes a token economy and step-level advancement system to promote the acquisition and utilization of a wide array of appropriate behaviors considered important for community living.

Assessment of delusions Prior to formal data collection, the subject met individually with the second

author over the course of several weeks. Clinical interviews, psychological assessments, and a review of hospital records were conducted to assess the phenomenology of the subject’s delusional beliefs. A list of questions addressing various aspects of these beliefs was developed. The subject was asked questions from this list, and modifications of the questions were made until a final list of 10 questions emerged that reliably elicited delusional answers.

The content of the subject’s delusions involved grandiose and bizarre ele- ments. He believed he was the son of Jesus and Mary and had the power to blow up the world if he so desired. He noted that he was in control of the United States government and that he owned the U.S. mint and a gold mine. He believed that he had been born with knowledge derived from many years of education and, thus, possessed several educational degrees. He also reported that his brain had been surgically removed as an infant, that his name on his hospital chart was incorrect, that his family members were not actually related to him, and that his “real” relatives had special powers similar to his own.

358 B. Himadi et al.

Strength of delusional beliefs Several authors have noted the multidimensionality of delusional beliefs

(Brett-Jones, Garety & Hemsley, 1987; Garety, 1985; Garety & Hemsley, 1987; Hole, Rush & Beck, 1979). Conviction or strength of belief, however, is the most characteristic and reliable feature of delusions (cf. Brett-Jones et al., 1987; Garety & Hemsley, 1987). The subject’s degree of conviction in his delusional beliefs was assessed throughout the study with a Likert scale card-sorting format. Five index cards were numbered one through five and colored from plain white (card one) through gray (card three) through black (card five), to visually repre- sent a five-point Likert scale. Visual and numerical representations of the scale were used to increase the subject’s comprehension of the Likert format. State- ments paraphrasing previously reported delusional self-statements, correspond- ing to the structured interview questions, were printed on separate strips of paper so that the subject could place each statement on the Likert scale card that best represented his degree of belief in the statement. In addition, neutral belief items about the weather and daily unit events that would be expected to change on a regular basis were used as “control” checks to further assess the subject’s understanding of the scale. Card one represented complete disbelief in the statement, card three for moderate certainty, and card five for absolute certainty about the statement.

Delusional verbalizations A brief interview involving the ten questions discussed above was used to

assess delusional verbalizations. The questions were asked in the same order throughout the study and were introduced to the subject with the experimenter’s statement “I want you to answer some questions.” The responses to all ten questions were audiotaped and later rated as delusional or nondelusional depending upon the content of the replies. If a particular answer was vague, a maximum of two verbal prompts were used to clarify the response. These two prompts were “Explain what you mean’’ and “Tell me more about it.” These prompts were used only occasionally and in all cases clarified a vague response as delusional or nondelusional.

Procedure The subject maintained his usual status within the unit program during the

duration of the study. Sessions took place twice per day on Tuesdays and Thurs- days in the experimenter’s office located on the unit. The experimenter (second author) conducted all regular assessments and the treatment intervention.

Delusions 359

The first meeting of the day was conducted at approximately 9:OO a.m. and involved the card-sort technique to assess the subject’s degree of conviction in the ten delusional statements. The five index cards were arranged in order from one to five on a desk in the experimenter’s office. The card-sorting pro- cedure was reviewed with the subject. The experimenter explained the meaning of each rating card, and the subject was required to paraphrase this explanation. The subject was then presented with the three neutral items about daily unit events and the weather, and he was required to rate these items as to strength of belief. For example, the subject was asked to rate the item “I will have salad at dinner this evening.” The subject then rated the 10 delusional statements. The experimenter read each statement to the subject, handed the strip of paper upon which the statement was printed to the subject, and the subject placed the statement on the card representing his strength of belief in the particular item. The 10 statements were rated in the same order according to the previously described format throughout the course of the study. The second meeting was held at approximately 3:30 p.m. and involved the 10-question interview discussed above.

Design The changing-criterion design (Hall & Fox, 1977; Hartmann & Hall, 1976;

Osborne & Himadi, 1990) was used to assess the effectiveness of the treatment procedures to alter delusional verbalizations. With this design, baseline obser- vations are initially obtained. Treatment proceeds in a series of criterion shifts and, in this case, each shift involvled a change in the answers to two interview questions. During each phase, a reinforcement contingency is placed on perform- ing at or beyond a particular criterion level. A stability criterion is required by having the subject perform at or near a specified level for a predetermined number of sessions. A more difficult criterion is then established until another stable level is obtained. Treatment proceeds in this way until the final criterion is achieved.

Experimental conditions

Baseline There were five baseline sessions. Each session involved the morning card

sort and afternoon interview. The subject was thanked for his participation following the completion of each assessment task.

360 B. Himadi et al.

Treatment No therapeutic contingencies were applied to the card-sort assessment task

at any point during the study. The treatment phase involved the 10-item clinical interview.

A training package including modeling, coaching, verbal prompts, behavior rehearsal, and differential verbal praise was used in this study. This training package was applied sequentially and cumulatively to the 10 interview questions in five, two-question criterion shifts. The first criterion, therefore, involved hav- ing the subject answer the first two interview questions in a nondelusional way. The subject was informed that he was to respond to the target questions “SO

that other people would agree with your answers.” If the subject could not give a correct answer, one was modeled by the experimenter. The subject then practiced answering the questions with the experimenter’s assistance until he could do so readily. A testing phase followed in which the subject was informed that the experimenter wanted to ask him some questions and, if he could answer the target questions as he did during training, he would receive a cup of coffee. The target questions were asked and, if answered correctly, the reinforcer was delivered immediately. The experimenter stated that she would ask some additional questions. The remaining questions were then asked and the subject was thanked for his participation and dismissed for the day. Training proceeded in this way until the subject could answer all 10 interview questions in a nondelu- sional manner.

Generalization assessment At the end of baseline and at the end of each criterion training phase, the

subject met individually with a novel interviewer to assess the extent to which training generalized to other persons. These interviewers asked the same 10 questions that the experimenter asked during the afternoon interview sessions. These generalization probes were conducted on off-training days and no rein- forcers were used for these generalization assessments. The subject was again thanked for his participation at the completion of the interview.

RESULTS

The audiotaped interviews were rated by a primary rater. Each response to the 10 interview questions was rated as delusional or nondelusional depending upon the content of the reply. A total of 15 interviews were randomly selected from baseline, training, and generalization sessions and independently rated

Delusions 36 1

by a second rater. Perfect interobserver reliability was found for all 150 responses from the 15 selected interviews.

Delusional verbalizations Figure 1 presents the data for the modification of the subject’s delusional

responses to the 10 interview questions. During Baseline (A), the subject gave delusional responses to all 10 of the experimenter’s questions. Inspection of the changing criterion phases (B,-B,) essentially reveals an orderly and stepwise decline in the frequency of delusional responses. With the exception of criterion B3, during which some fluctuation in responding occurred and in which the subject consistently answered an untrained item in a nondelusional way, all declines reflect the changing criterion requirements for reinforcement. By the fifth criterion change (B,), all answers to the experimenter’s questions were nondelusional.

The results for the 3-week follow-up assessment shows a resumption of delu- sional responding to 4 of the 10 interview questions. Three of these four responses involved the last three tra.ining items.

Generalization Probes The results for the generalization probe conversations are also presented

in Figure 1. The first generalization interview following baseline resulted in delusional responding to all of the interviewer’s questions. Following criterion B,, and consistent with the training for this phase, the subject answered the first two items in a nondelusional way. The results following criterion shift B2 revealed that the subject gave an additional nondelusional response to a question that was not the focus of training; there were two additional appropri- ate responses following criterion B,. All other responses during these two inter- views were essentially consistent with the responses given during the corresponding training trials.

The subject answered the first eight questions consistent with the training for nondelusional responding during the generalization interview following the fourth criterion training phase. All .the subject’s responses were rated as nondelu- sional during the final generalization probe. A generalization interview was not obtained during follow-up.

Delusional beliefs The results from the card-sort assessment for strength of belief revealed a

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Delusions 363

a rating of five to each of the 10 ddusional statements for the entire duration of the study. A rating of five reflects absolute certainty about the statement. The subject appropriately assigned different ratings to the three neutral items depending upon the status of the weather and daily unit events.

DISCUSSION

Consistent with previous studies that used reinforcement contingencies to alter delusional verbalizations (e.g., Ayllon & Haughton, 1964; Liberman et al., 1973; Patterson & Tiegen, 1973; Wincze et al., 1972), this single-subject demonstration revealed that changes were effected in delusional replies to per- sonal background questions of a chronically mentally ill inpatient.

The changing-criterion design provided a convincing demonstration of the experimental control exercised by the treatment intervention. The 10 interview questions were divided into five, two-question criterion units, and the treatment package was applied sequentially and cumulatively to these five criteria. A step- wise and orderly decline in the rate of delusional responses was obtained that corresponded well to the changing criterion values. Only one instance of consis- tent criterion contamination, or independence violations (cf. Hartmann & Hall, 1976), occurred in this study. The subject consistently gave a nondelusional reply to an untrained item during phase B3.

During the 3-week follow-up interview, 4 of 10 questions resulted in delusional responses. While practical considerations precluded more extensive follow-up, it would appear that maintaining and gradually fading the controlling contingen- cies would be important for the control of delusional verbalizations. Contingen- cies used on a ward-wide basis to control delusional verbalizations are difficult to arrange, however, and typically result in an incomplete suppression of the bizarre verbalizations (cf. Ayllon 6t Michael, 1959; Davis et al., 1976; Wincze et al., 1972).

The results from the generalization interviews were encouraging. With only three exceptions, all responses during these generalization probes were consis- tent with those responses given during the training test trials. Since generaliza- tion tests were conducted with novel partners and in different locations on the ward during every probe, both generalization across person and location were obtained. The same interview was used for both training and generalization trials, however, and thus is not the most stringent test of generalization effects. Future studies could examine the impact of training to more naturalistic ward interactions and to psychiatric interviews. Previous studies on the modification of delusional verbalizations have found no effects for these types of generaliza-

364 B. Himadi et al.

tion tests (cf. Alford et al., 1982; Davis et al., 1976; Liberman et al., 1973; Patterson & Tiegen, 1973; Wincze et al., 1972). Only partial generalization effects have been obtained when similar tests were used for both training and generalization trials (cf. Liberman et al., 1973; Patterson & Tiegen, 1973).

Interestingly, no changes were obtained on the ratings of intensity of belief for the 10 delusional statements. The subject assigned a rating of absolute cer- tainty to all of the statements throughout the course of the study. Thus, the subject’s delusional beliefs remained unchanged while change was effected in his delusional verbalizations.

It is unlikely that the results on the delusional belief ratings were due to some type of response set given the spread of ratings obtained for the neutral items. And since the belief ratings were always obtained during the morning sessions, two assessment probes were conducted in which the belief ratings were obtained approximately 2 hours after a delusion verbalization session to see if this would affect the belief ratings in any way. There were no changes in the belief ratings during these probes.

While replication procedures are necessary to establish the degree of generality of the results obtained in this study, the results are consistent with Alford’s (1 986) contention that behavioral treatment of delusional verbalizations does not insure the reduction of delusional beliefs. Given the results of this prelimi- nary investigation and the limited generalization effects obtained from previous verbal conditioning studies, examination of psychosocial procedures for the modification of delusional private events may prove fruitful.

There are encouraging trends developing in the literature on delusional belief modification. The results from studies in this area are promising even though appropriate experimental control procedures are lacking in several of the investi- gations (cf. Alford, 1986; Chadwick & Lowe, 1990; Hartmann & Cashman, 1983; Johnson et al., 1977; Lowe & Chadwick, 1990; Milton et al., 1978; Rudden, Gilmore & Francis, 1982; Watts, Powell & Austin, 1973). Further development and testing of behavioral procedures for the alteration of delusional beliefs is clearly warranted.

REFERENCES

Alford, B. A. (1986). Behavioral treatment of schizophrenic delusions: A single-case experimental analysis. Behavior Therapy, 17, 637-644.

Alford, G. S., Fleece, L., & Rothblum, E. (1982). Hallucinatory-delusional verbalizations: Modifi- cation in a chronic schizophrenic by self-control and cognitive restructuring. Behavior Modijica- tion, 6(3), 421435.

American Psychiatric Association (1987). Diagnostic and statistical manual of mental disorders (3rd ed. revised). Washington, DC: Author.

Delusions 365

Ayllon, T., & Haughton, E. (1964). Modification of symptomatic verbal behavior of mental patients. Behaviour Research and Therapy, 2, 87-97.

Ayllon, T., & Michael, J. (1959). The psychiatric nurse as a behavioral engineer. Journal of the Experimental Analysis of Behavior, 2, 323-334.

Brett-Jones, J. R., Garety, P. A., & Hemsley, D. R. (1987). Measuring delusional experiences: A method and its application. British Journal of Clinical Psychology, 26(4), 257-265.

Bulow, H., Oei, T. P. S., & Pinkey, B. (1979). Effects of contingent social reinforcement with delusional chronic schizophrenic men. Psychological Reports, 44,659-666.

Burgio, L., Brown, K., & Tice, L. (1985). Behavioral covariation in the treatment of delusional verbalization with contingency management. Journal of Behaviour Therapy and Experimental Psychiatry, /6(2), 173-182.

Cayner, T. J., & Kiland, J. R. (1974). Use of brief time-out with three schizophrenic patients. Journal ofBehaviour Therapy and Experimental Psychiatry, 5 , 141-145.

Chadwick, P. D. J., & Lowe, C. F. (1990). Measurement and modification of delusional beliefs. Journal of Consulting and Clinical Psychology, 58(2), 225-232.

Davis, J. R., Wallace, C. J., Liberman, R . P., & Finch, B. E. (1976). The use of brief isolation to suppress delusional and hallucinatory speech. Journal of Behaviour Therapy and Experimental Psychiatry, 7,269-275.

Foxx, R. M., McMorrow, M. J., Davis, L. A,, & Bittle, R. G. (1988). Replacing a chronic schizophrenic man’s delusional speech with stimulus appropriate responses. Journal of Behav- iour Therapy and Experimental Psychiatry, 19,43-50.

Garety, P. (1 985). Delusions: Problems in definition and measurement. British Journal of Medical

Garety, P. A., & Hemsley, D. R. (1987). Characteristics of delusional experience. European Archives of Psychiatry and Neurological Sciences, 236(5), 294-298.

Hall, R. V., & Fox, R. G. (1977). Changing-criterion designs: An alternative applied behavior analysis procedure. In B. C. Etzel, J. h4. LeBlanc & D. M. Baer (Eds.), New developments in behavioral research: Theory, method, and application. In honor of Sidney W. Bijou. Hillsdale, New Jersey: Erlbaum.

Hartmann, D. P., & Hall, R . V. (1976). The changing criterion design. Journal of AppliedBehavior Analysis, 9(4), 527-532.

Hartman, L. M., & Cashman, F. E. ( I 983). Cognitive-behavioral and psychopharmacologicaI treatment of delusional symptoms: A preliminary report. Behavioural Psychotherapy, //( l),

Haynes, S. N. (1986). A behavioral model of paranoid behaviors. Behavior Therapy, 17,266-287. Hole, R. W., Rush, A. J., & Beck, A. I-. (1979). A cognitive investigation of schizophrenic

delusions. Psychiatry, 42, 3 12-3 14. Johnson, W. G., Ross, J. M., & Mastria, M. A. (1977). Delusional behavior: An attributional

analysis of development and modification. Journal of Abnormal Psychology, 86(4), 421426. Kennedy, T. (1964). Treatment of chronic schizophrenia by behaviour therapy: Case reports.

Behaviour Research and Therapy, 2, 1-6. Liberman, R. P., Teigen, J., Patterson, R., & Baker, V. (1973). Reducing delusional speech

in chronic, paranoid schizophrenics. Journal of Applied Behavior Analysis, 6,57-64. Licht, M. H. (1984). Assessment of client functioning in residential settings. In M. Mirabi (Ed.),

The chronically mentally ill: Research andservices. New York: SP Medical and Scientific Books. Lowe, C. F., & Chadwick, P. D. J. (1990). Verbal control of delusions. Behavior Therapy, 21,

461479. Maher, B., & Ross, J. S. (1984). Delusions In H. E. Adams & P. B. Sutker (Eds.), Comprehensive

handbook of psychopathology (pp. 383409). New York: Plenum. Milton, F., Patwa, V. K., & Hafner, R. J. (1978). Confrontation vs. belief modification in persis-

tently deluded patients. British Journal of Medical Psychology, 51, 127-1 30. Nydegger, R. V. (1972). The elimination of hallucinatory and delusional behavior by verbal

Psychology, 58( l), 25-34.

50-6 1.

366 B. Himadi et al.

conditioning and assertive training: A case study. Journal of Behaviour Therapy and Experimen- tal Psychiatry, 3,225-227.

Osborne, M. L., & Himadi, B. (1990). Evaluation of a shaping procedure with the changing- criterion design. Behavioral Residential Treatment, 5(2), 75-8 1.

Patterson, R. L., & Teigen, J. R. (1973). Conditioningand post-hospital generalization of nondelu- sional responses in a chronic psychotic patient. Journal of Applied Behavior Analysis, 6,65-70.

Paul, G. L. (1987). The time-sample behavioral checklist: Observafional assessment instrumentation for service and research. Champaign, Illinois: Research Press.

Paul, G. L., & Lentz, R. J. (1977). Psychological treatment of chronic mental patients: Milieu versus social learning programs. Cambridge, Massachusetts: Harvard University Press.

Paul, G . L., & Mariotto, M. J. (1987). TSBC code and higher-order score normative distributions, internal relationships and relative stabilities. In G. L. Paul (Ed.), The time sample behavioral checklist: Observational assessment instrumentation for service and research (pp. 95-146). Cham- paign, Illinois: Research Press.

Rickard, H. C., Dignam, P. J . , & Horner, R. F. (1960). Verbal manipulation in a psychotherapeutic relationship. Journul of Clinical Psychology, 16, 36k-367.

Rudden, M., Gilmore, M., & Frances, A. (1982). Delusions: When to confront the facts of life. American Journal of Psychiatry, 139(7), 929-932.

Sanders, R . M. (1971). A timeout procedure for the modification of speech content-A case study. Journal of Behaviour Therapy and Experimental Psychiatry, 2, 199-202.

Schraa, J. C., Lautmann, L., Luzi, M. K., & Screven, C. G. (1978). Establishment of nondelusional responses in a socially withdrawn chronic schizophrenic. Journal of Applied Behavior Analysis, 11,433434.

Varni, J. W., Russo, D. C., & Cataldo, M. F. (1978). Assessment and modification of delusional speech in an 1 1-year-old child: A comparative analysis of behavior therapy and stimulant drug effects. Journal ofBehaviour Therapy and Experimental Psychiatry, 9,377-380.

Watts, F. N., Powell, G. E., & Austin, S. V. (1973). The modification of abnormal beliefs. British Journal of Medical Psychology, 46, 359-363.

Wincze, J. P., Leitenberg, H., & Agras, W. S. (1972). The effects of token reinforcement and feedback on the delusional verbal behavior of chronic paranoid schizophrenics. Journal of Applied Behavior Analysis, 5 , 247-262.

Winters, K. C., & Neale, J. M. (1983). Delusions and delusional thinking in psychotics: A review of the literature. Clinical Psychology Review. 3(2), 227-253.

Wolff, R. (1971). The systematic application of the satiation procedure to delusional verbiage. The Psychological Record, 21,459463.

World Health Organization (1973). The internutionulpilnt study ofschizophrenia. Geneva: WHO.