Subtest Scatter and Premorbid Intelligence: Lessons from the WAIS-R Standardization Sample

This study was carried out to underscore that the psychometric properties of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) make it risky for a clinician to utilize, in isolation, an individual's highest WAIS-R subtest score as a robust measure of that person's supposedly higher level of "premorbid" intelligence, or, furthermore, to interpret the individual's lowest WAIS-R subtest scores as indices of an "impairment" in the brain-behavior functions believed to be mirrored by these low subtest scores. Analyses revealed that sizeable differences (M = 6.66 points) between the highest and lowest WAIS-R subtests were the norm rather than the exception for the 1,880 Ss used in the standardization of this scale. Related psychometric properties of the scale that also bear on the use of the WAIS-R in isolation for determining either premorbid level of intelligence or current impairment are also discussed.