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In a free emission task, normals, chronic schizophrenics with only positive and those with only negative symptoms generated as many exemplars from natural language categories as they could in three minutes. While the overall output level of both schizophrenic groups was lower than that of the normals, neither showed intrusions of unrelated words, and the temporal distribution of the output was marked by a clustering pattern inconsistent with a selective attention deficit hypothesis. The schizophrenics with negative symptoms tended to produce consistently smaller clusters than the normals and the schizophrenics with positive symptoms, implicating a specific retrieval constriction. The relationship of this to the major negative symptom poverty of speech is discussed.

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The target detection performance of normals, chronic schizophrenics with positive symptoms and those with negative symptoms was compared in focused and divided attention conditions. The focused condition involved the monitoring of one, and the divided condition the monitoring ofboth, ofthe dichotically presented word lists. The amount and rate of list presentations were held constant across the conditions in an attempt to separate attentional from difficulty and capacity factors. Results showed that while the overall performance of both schizophrenic groups was lower than that of the normals, their performance change from the focused to the divided attention condition did not differ from that ofthe normals. These results do not support a schizophrenic selective attention deficit hypothesis.The concept selective attention denotes the voluntary control over the direction of attention, and schizophrenics have long been characterized as deviant in this respect. Kraepelin (1919) noted that some patients showed a kind of irresistible attraction of attention to casual external impressions. With McGhie &Chapman's (1961) report of the subjective experiences of newly admitted schizophrenics' inability to organize selectively and control incoming information, the selective attention hypothesis, which views the schizophrenic as the passive victim of irrelevant and distracting information, became the dominant paradigm.which assume that some selection defect is present in schizophrenia. Early models assumed faulty sensory selection, but more recent models specify more precisely that the faulty selection device is that operating after sensory analysis has been adequately carried out, e.g. Frith (1979) and Hemsley & Richardson (1980). Experimental studies have offered varying and inconclusive evidence, and it is far from clear that there is a schizophrenic-specific selective attention deficit at any level. Digit recall tasks and shadowing tasks have been widely used for manipulating the presence-absence of distractors. Generally these try to show a differential schizophrenic-normal fall in performance with the introduction of distraction.Based on McGhie's reports and similar evidence, many models have been devised Digit recall tasksLawson et al. (1967) showed that while schizophrenic performance was worse than that of normals, the magnitude of this difference increased in the distraction condition. However, Berg & LeventhaI(l977) among others found that while schizophrenics performed worse than a group of non-schizophrenic psychotic controls, distraction did not produce a . differential effect. Hemsley & Zawada (1976), using a pre-and post-instruction procedure, found that while normals benefited from pre-instruction, both schizophrenics and depressives did not, and therefore exhibited susceptibility to distraction. Oltmanns et al. (1978) found in one study that schizophrenics were more impaired in the distraction condition than psychiatric controls, but only for long subtasks. In another study they found this kind ofdifferen...

SynopsisThe present study examined a prominent symptom subtype conception of the psychopathology of schizophrenia. It analysed the presumed dichotomy between hallucinations, delusions and formal thought disorder as positive symptoms and flattening of affect and poverty of speech as negative symptoms, and tested predictions concerning the nature of the mediating processes of positive and negative symptoms. Four different analyses were applied to the transcripts of speech produced by 9 normals, 10 chronic schizophrenics with only positive symptoms of whom 7 had incoherence of speech, and 9 chronic schizophrenics with only negative symptoms of whom 4 had poverty of speech. The conception of the nature of the mediating processes of positive and negative symptoms was not supported by the results. Further, a clear dichotomy between positive and negative symptom groups was not shown to exist, because positive speech disorder and negative speech disorder did not follow the presupposed dichotomy. Thus, contrary to existing conceptions of speech disorder in schizophrenia, both positive and negative speech disorder are marked by poverty of thought, as measured by the production of fewer and shorter ideas and lower speech variability.