A proposed method to estimate premorbid intelligence utilizing group achievement measures from school records

Estimating premorbid cognitive functioning is an important part of any neuropsychological evaluation. This estimate is the benchmark against which current cognitive functioning is compared to establish the existence, degree, and rate of cognitive decline. Typically methods used to estimate premorbid cognitive functioning are based on; (1) demographic information, (2) combined current test performance with demographics, and (3) current reading (word recognition) ability. These approaches each have drawbacks including difficulty estimating premorbid abilities of people close to the extremes of intellectual functioning (i.e., estimating the premorbid ability of individuals in the gifted or borderline intellectual ranges). The current study reviewed the existing data comparing commonly used group administered achievement and college board tests with the Wechsler IQ tests. It is proposed that clinicians may predict premorbid cognitive functioning by applying the well-known predicted-difference method to estimate IQ from group administered achievement test scores. The correlations between group administered achievement and college board tests with the Wechsler IQ tests are reviewed and the descriptive statistics of selected group administered achievement and college board tests are presented.