Limited accuracy of premorbid intelligence estimators: A demonstration of regression to the mean

Regression-based premorbid intelligence estimators have been devised by Bar ona, Reynolds, and Chastain (1984), Barona and Chastain (1986), Hamsher (19 84), Krull, Scott, and Sherer (1995; the Oklahoma Premorbid Intelligence Es timate: OPIE), and Vanderploeg, Sckinka, and Axelrod (1996; BEST-3 approach ), but little is known of their relative accuracy, particularly in outer ra nges of intellectual ability (e.g., below-average, superior, etc.). Towards this end, the Wechsler Adult Intelligence Scale-Revised (WAIS-R) was admin istered to 150 neurologically normal adults, and estimated VIQ, PIQ, and FS IQ scores were computed according to each regression method. Results showed that methods based solely on demographic factors were most susceptible to meanward regression, rendering them poor estimators of IQ scores in outer r anges. Although the OPIE and BEST-3 performed somewhat better, their accura cy remained relatively weak. The findings suggest that: regression-based es timates of premorbid IQ are very susceptible to error, particularly in oute r ranges of intellectual function.