A comparison of abstractive and nonabstractive deficits in schizophrenics and psychiatric controls.

Chapman and Chapman (Disordered Thought in Schizophrenia, Appleton-Century-Crofts, New York, 1973) have suggested that findings of abstract thinking deficits in schizophrenia could be functions of control task artifacts. This paper describes two projects in which the abilities of schizophrenics and psychiatric hospital controls who had been closely matched on a wide variety of vocabulary and nonvocabulary control tasks to perform several types of abstract thinking tasks were compared. No differences on the mean scores of the schizophrenic and control patients appeared on four of five measures used. On the fifth, a logical reasoning test, the schizophrenics were inferior to controls. The results suggest that many of the differences reported earlier between schizophrenics and nonschizophrenics on abstraction tasks may result from the heavy reliance of researchers on vocabulary as a control matching test, and its peculiar resistance to deterioration in schizophrenia. The results also suggest that inability to use logic properly may be.