Patterns of Age-Related IQ Changes from the WAIS to WAIS-III after Adjusting for the Flynn Effect

Abstract

Previous studies have found that the Flynn effect accounts for at least 48%, and as much as 100%, of the difference between norms for 20- and 70-year-olds on the Wechsler intelligence tests (Dickinson & Hiscock, 2010). The purposes of the current study are 1) to obtain a true aging effect (TAE) for each of the 11 subtests of the Wechsler intelligence tests by comparing norms for different age groups and adjusting them for the Flynn effect, and 2) to compare three methods of calculating the age group difference (AGD), Flynn effect difference (FED), and TAE for a cohort across successive revisions of the Wechsler test. Results are consistent with previous findings of a large contribution of the Flynn effect to age differences in norms for the Wechsler IQ tests. Moreover, IQ was found to be relatively stable, on average, across various age groups. In order to most accurately determine age-group differences in IQ, methods involving direct assessment of the Flynn effect from the subtest norms are preferable to the use of Flynn effect estimates from the publisher’s validity samples.