Problems in the interpretation of cognitive abnormalities in schizophrenia.

This study compared matched groups of patients with acute schizophrenia and with depression on three tests used in the assessment of schizophrenic thinking disorder. Most measures derived from these tests significantly differentiated the groups; however, within the schizophrenic group there were no significant correlations between scores on the three tests. Further data were available from a choice reaction-time card-sorting task, from which estimates of distractability, stimulus decision time, response decision time, and movement time, were obtained. Only one significant relation was found between these measures and scores on the clinical tests. The possible confounding effects of intelligence and responsiveness are discussed. It is argued that more direct measures of the latter are preferable to interpreting tests of thinking disorder in terms of information processing deficits.