The diagnostic significance of overinclusive thinking in an unselected psychiatric population.

Abstract

Cameron (1938, 1939) suggested that schizophrenic thought disorder is largely the result of overinclusive thinking, which he defined as the inability to preserve conceptual boundaries. Payne, Matussek and George (1959) developed a battery of objective measures of overinclusive thinking, which they found differentiated between an acute schizophrenic and a neurotic control group. Payne and Hewlett (1960) found that a battery of tests of overinclusive thinking intercorrelated as expected. They were able to obtain a factor score from their overinclusion test battery which differentiated a group of acute schizophrenic patients from control groups of depressives, neurotics and normal subjects. Payne and Friedlander (1962), on the basis of this factorial study, suggested a short battery of three measures of overinclusive thinking consisting of the number of ‘Non-A’ or unusual responses to the Object Classification Test (Payne, 1962), the average number of words used in explaining the Benjamin Proverbs given under special 'stress free’ instructions, and the average number of objects classified together in the ‘handing over’ section of the Goldstein-Scheerer Object Sorting Test. This standard test battery has been the operational definition of overinclusive thinking in a number of studies. Only one study of the reliability of this test battery appears to have been carried out. Hawks and Payne (1971) report the correlations obtained from a group of 54 psychiatric inpatients who were retested after a 4-day interval. The test-retest correlation coefficient (uncorrected) obtained from the Combined Transformed score (Payne and Friedlander, 1962) was 0 · 87. The reliabilities of the individual tests ranged from 0·77 to 0·86.