Evidence for organicity in concrete vs. overinclusive thought-disordered schizophrenics.

Matched 20 overinclusive schizophrenics, 13 schizophrenics with a concrete thought disorder, defined in terms of performance errors on a conceptual ability test, and 11 brain-damaged patients on age, education, vocabulary proficiency, severity of illness and length of hospitalization. Ss then were given the Combined Test Battery for Organicity. No differences were found between the overinclusive and concrete schizophrenics on any measure of organicity. The Organic Test Battery had poor concurrent validity in distinguishing between brain-damaged and schizophrenic patients. Schizophrenics with a concrete thought disorder have a relatively rare condition that continues to defy explanation, though on the basis of past research an organic involvement seems to be the most parsimonious explanation.