Negative features, retrieval processes and verbal fluency in schizophrenia.

Twenty chronic schizophrenic patients, ten matched normal controls and nine depressed controls performed categorical verbal fluency tasks for three minutes each on five separate occasions. On each occasion the schizophrenic patients generated significantly fewer words than the controls. Comparison of the different occasions showed that the schizophrenic patients had as many words available in their inner lexicons but were inefficient in retrieving them. The schizophrenic patients also generated fewer clusters of related words and more words outside the specified category. Reduced ability to generate words while the lexicon remained intact was more marked in patients with negative features. Patients with incoherence, in contrast, were more likely to produce inappropriate words. We propose that both poverty of speech and incoherence of speech reflect problems in the retrieval of words from the lexicon. To cope with these problems patients with poverty of speech terminate their search prematurely while the patients with incoherence commit errors in selecting words for output.