Background: The National Adult Reading Test (NART) is widely used in research and clinical practice as an estimate of pre-morbid or prior ability. However, most of the evidence on the NART's validity as a measure of prior intellectual ability is based on concurrent administration of the NART and an IQ measure.
Method: We followed up 179 individuals who had taken an IQ test (the Moray House Test) at age 11 and administered the NART and the Mini-Mental State Examination (MMSE) at age 77. A subset (N = 97) were also re-administered the original IQ test.
Results: The correlation between NART performance at age 77 and IQ age 11 was high and statistically significant (r = 0.73; P < 0001). This correlation was comparable to the correlation between NART and current IQ, and childhood IQ and current IQ, despite the shared influences on the latter variable pairings. The NART had a significant correlation with the MMSE but this correlation fell to near zero (r = 0.02) after partialling out the influence of childhood IQ.
Discussion: The pattern of results provides strong support for the claim that the NART primarily indexes prior (rather than current) intellectual ability.