Assessment of conceptual deficits in brain-damaged and schizophrenic patients.

Five concept-formation scores for 20 brain-damaged and 20 schizophrenic inpatients were factor analyzed, along with WAIS Vocabulary and Block Design. One factor emerged from this analysis, suggesting that these concept-formation tests do not measure an ability which is greatly different from general intelligence when administered to patients of the type studied. None of the single concept-formation scores discriminated between the brain-damaged and schizophrenic groups independently of general intellectual level, although an exploratory analysis of the subtests of the Halstead Category Test indicated that differential performance on Subtest IV versus Subtest V produced valid criterion variance beyond that attributable to Vocabulary and Block Design alone. The findings were discussed in terms both of the factors underlying the performance of the present subjects versus those from different patient populations, and the need for refining ability-oriented diagnostic strategies when studying impaired patients who do not manifest highly specific psychological deficits on standard clinical tests yielding single scores.