Comparison of Wechsler Adult Intelligence Scale Indices of Cerebral Dysfunction

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Abstract
This study assessed and compared the diagnostic accuracies of eight cerebral dysfunction indices based upon the Wechsler Adult Intelligence Scale (WAIS). Patients with extreme values of the Halstead Impairment Index were used to compose Impaired and Not Impaired groups. The Impaired group did significantly worse than the Not Impaired group on all 11 WAIS subtests, and there was little overlap between the groups in Full Scale IQ. The WAIS cerebral dysfunction indices ignore such differences in over-all level of performance and instead use patterns of subtest scores in making diagnostic classifications. Seven of the eight indices predicted impairment status at levels which exceed chance, but the total correct classification rates were quite modest. Statistical correction for group age differences reduced classification rates even more. Deviation score analyses were employed to assess relative strengths and deficits on the WAIS subtests, controlled for over-all level of performance. Compared to the Not-impaired group, Impaired subjects did relatively poorly on Block Design and Object Assembly, and relatively well on Information, Comprehension, Vocabulary, and Picture Completion. Significant education effects and education by impairment status interactions also occurred for several subtests. It was concluded that the WAIS indices have limited value in screening for cerebral dysfunction, and reasons for this were discussed.