Change in cognitive functioning is an important aspect of human aging and a key outcome in many medical conditions. However, cognitive change can rarely be measured directly, since prior cognitive data do not exist for most people. We examined the criterion validity and one-year stability of the difference between National Adult Reading Test…

Two studies (N=4,261 persons) illustrate an inverse relationship between ability level and correlations among IQ measures. Low IQ subjects showed higher correlations than did high IQ subjects. Intercorrelations of IQ subtests, intercorrelations of cognitive ability measures, and correlations of IQ with measures of cognitive ability displayed the…