Reasoning in deluded schizophrenic and paranoid patients: biases in performance on a probabilistic inference task

Article Abstract:

While delusions are one of the most common symptoms in psychiatry, the underlying psychological processes are poorly understood. One theory is that they are a product of normal reasoning - a person's attempt to account for strange perceptions. Studies have also shown evidence that reasoning may be abnormal in deluded individuals, however. A study was designed with four groups of subjects: 13 schizophrenic subjects; 14 paranoid/delusional subjects; 14 subjects in the anxious control group; and 13 in the normal control group. The first two groups suffered delusions whereas the last two did not. Each subject was exposed to two conditions. Subjects were first tested on the number of trials they required before reaching a decision about the probability of a colored bead coming from one jar or another, and on the second task they were tested on their ability to reach a decision on the probability after a set 20 trials. It was found that subjects in the two deluded groups requested less information before reaching a decision regarding probability than nondeluded subjects. In fact, 41 percent of the deluded subjects reached a decision after only one bead was presented. They were also more likely to question their decisions after being confronted with contradictory information. The latter result is evidence for the importance of immediate environmental stimuli over prior learning experiences in deluded subjects, and the hypothesis that abnormal perceptual experiences (i.e., environmental stimuli) may interact with reasoning ability. This does not support the hypothesis that deluded subjects reason normally about abnormal experiences. (Consumer Summary produced by Reliance Medical Information, Inc.)

Tests, problems and exercises, Cases, Testing, Reasoning, Paranoid disorders, Paranoia, Paranoid personality disorder

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Linguistic and cognitive failures in schizophrenia: a multivariate analysis

Article Abstract:

To learn more about the relationship between cognitive performance and language function, 38 schizophrenics, 30 manic patients, and 25 normal subjects underwent evaluation. Subjects were tested for their abilities to perform cognitive tasks (auditory distractibility, reality monitoring, and word span/encoding), as well as for the disorders of verbal communication expressed as thought disorder and reference failures. Thought disorder was determined by two trained raters, who listened to tapes of 15-minute open-topic interviews and rated the extent of thought disorder present. Positive thought disorders were those associated with the production of thought that is incoherent or illogical (among other aspects), while negative thought disorders were those characterized by poverty of speech and speech content. Linguistic ratings were done for the same taped material. Results showed that positive (but not negative) thought disorder in schizophrenics correlated with deficits in two types of auditory, verbal information processing: distractibility (performance under verbal distraction) and reality monitoring (recognition by the subject of words he had said or thought). These deficits were not found for manic patients, suggesting that, although both illnesses are associated with a communication disorder, different processes underlie them. A discussion of negative and positive thought disorder is provided. (Consumer Summary produced by Reliance Medical Information, Inc.)

Psychological aspects, Analysis, Language and languages, Cognition disorders, Cognitive disorders, Language disorders

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