Estimation of WAIS-R premorbid intelligence: Current ability and demographic data used in a best-performance fashion

The validity of a technique for estimating premorbid intellectual functioning based on Wechsler Adult Intelligence Scale-Revised (WAIS-R; D. Wechsler, 1981) subtest performance and demographic information used in a best-performance fashion was investigated. Premorbid IQ scores were predicted using the highest score from (a) all 11 R.D. Vanderploeg and J.A. Schinka (1995) regression equations (BEST-11) and (b) the 3 most robust regression equations (BEST-3). These results were compared with premorbid estimates based solely on demographic information. In the WAIS-R standardization sample the BEST methods were more highly correlated with actual WAIS-R IQ than were A. Barona et al. (1984) estimates. The BEST-11 and BEST-3 approaches resulted in overestimates of about 9 points and 5 points, respectively. In matched samples of neurologic patients and normal controls, Pearson correlations between actual and estimated IQ scores were significantly higher for the BEST-3 than the Barona et al. method. The BEST-3 method also was superior at predicting group membership (normal vs. brain-damaged). These studies support the use of the BEST-3 approach to premorbid estimation of cognitive abilities.