Estimating premorbid intelligence by combining the NART and demographic variables: An examination of the NART standardisation sample and supplementary equations

Abstract

There are two main approaches to the estimation of premorbid intelligence. One of these uses an oral reading test, the National Adult Reading Test (NART). The other estimates premorbid intelligence from demographic variables. It was recently reported that combining the NART and demographic variables in a multiple regression equation provides more accurate estimation of IQ than is afforded by either method alone. The present study was undertaken to determine if this finding would hold in another sample. The sample employed ( n = 120) was that used to originally standardise the NART against the WAIS. Combining demographic variables (age, sex, social class) with the NART significantly increased predicted variance over use of the NART alone. The NART standardisation sample had been administered a short-form of the WAIS. This sample was combined with additional subjects ( n = 151) to produce new equations for the estimation of premorbid IQ. The equations permit clinicians to estimate a client's premorbid intelligence with the NART/demographic method when time pressures have necessitated the use of a short-form WAIS as the current IQ measure.