Investigations of performance on cognitive tasks usually result in the findings that normal subjects achieve the highest mean scores, schizophrenic subjects are intermediate, and subjects with organic brain disease perform most poorly. The range of performance of schizophrenic patients is usually quite broad, overlapping with that of good normal subjects, at one extreme, and with that of poor-performing patients with organic disease, at the other. However, the pattern of error scores of the schizophrenic subjects does not distinguish their performance from that of these other clinical groups. It seems likely, therefore, that such data reflect only nonspecific impairment of cognitive function. The degree of such impairment is usually less in randomly chosen groups of schizophrenic subjects than that found in similarly chosen groups of patients with organic brain disease.*Since cognition in these patient groups grossly differs in many respects, one must conclude