Retrospective validation of WTAR and NART scores as estimators of prior cognitive ability using the Lothian Birth Cohort 1936

In order to assess the degree of cognitive decline resulting from a pathological state, such as dementia, or from a normal aging process, it is necessary to know or to have a valid estimate of premorbid (or prior) cognitive ability. The National Adult Reading Test (NART; Nelson & Willison, 1991) and the Wechsler Test of Adult Reading (WTAR; Psychological Corporation, 2001) are 2 tests developed to estimate premorbid or prior ability. Due to the rarity of actual prior ability data, validation studies usually compare NART/WTAR performance with measures of current abilities in pathological and nonpathological groups. In this study, we validate the use of WTAR scores and extend the validation of the use of NART scores as estimates of prior ability, vis-à-vis the actual prior (childhood) cognitive ability. We do this in a large sample of healthy older people, the Lothian Birth Cohort 1936 (Deary, Gow, Pattie, & Starr, 2012; Deary et al., 2007). Both NART and WTAR scores were correlated with cognitive ability tested in childhood (r = .66-.68). Scores on both the NART and the WTAR had high stability over a period of 3 years in old age (r in excess of .90) and high interrater reliability. The NART accounted for more unique variance in childhood intelligence than did the WTAR.