The study attempted to separate effects of length of illness and length of hospitalization on vocabulary and concept formation performance of chronic schizophrenic and nonpsychiatric patients. Patients were approximately matched for length of illness, but differed in time spent in hospitals (several years or a few months); they were compared on vocabulary associative interference and on concept formation indices from the Object Sorting Test. Schizophrenic inpatients and outpatients were subdivided into paranoids and nonparanoids and equated on severity of disturbance. Results indicated that both prolonged hospitalization and diagnostic status are associated with thought disorder, especially associative intrusions in vocabulary and idiosyncratic thinking. These indices also appear most efficient in distinguishing between schizophrenic and nonpsychiatric patients and between paranoid and nonparanoid schizophrenics.Consistent with the theoretical and clinical emphases on disorganized thinking in schizophrenia, a good deal of research effort has been directed at the evaluation of various deficits in schizophrenic cognition (e.g., Bleuler, 1950;Payne, 1973). Typically, research subjects have been drawn almost exclusively from hospitalized populations, as past policies had virtually guaranteed that "unimproved" schizophrenics would remain hospitalized. As a result, researchers had to settle for conditions where the variables of length of illness (chronicity) and length of hospitalization are confounded. Thus, performance deficits in chronic schizophrenics could be interpreted as originating from the chronic illness "process" itself, or from the lengthy and unbroken stay within the confines of usually suboptimal institutional environments or, more safely, from some unknown combination of the two. Each of these interpretations has had its advocates and its critics (e.g., Goffman, 1962;Klerman, 1977;Strauss, 1973;Wing, 1962), and has far-ranging implications for both patients and society. Yet, as the results of recent studies (e.g., Raps, Peterson, Jonas & Seligman, 1982;Taylor, 1979) that set about investigating patient behaviour Based on a doctoral dissertation by the first author under the supervision of the second author. Special thanks to the members of the dissertation committee A. Clark, D. Crockett, the late P. Davidson, and R. Hakstian, and to several anonymous reviewers of earlier versions of this article.Requests for reprints should be addressed to Demetrios Papageorgis,
