The Wechsler Adult Intelligence Scale (WAIS) has been widely used in research as well as in clinical applications. Much of what is believed to be known about adulthood intellectual development is based on research with the WAIS. The conclusions that can be drawn from this WAIS research are often clouded and sometimes contradictory. The results have mixed implications in regard to important questions concerning the factorial structure, developmental sequences and changes, and, in general, the construct validity of the WAIS. During the past two years WAIS data has been collected from surveys of the research literature and from direct contact with researchers and clinics. WAIS summary data, subscale scores, item data and other information on over 40,000 individual subjects has been obtained from over 100 different experimental studies. These data have been coded and stored in a computerized databank and are being used in a large-scale mega-analysis of the WAIS. Initial analyses of these data has focused on the subpopulation of 13,632 healthy adults ranging in age 15 to 95 from 41 different USA experiments. Probabilistic and statistical stratification procedures have been used to select specialized subsamples of interest. Cross validation strategies based on multistage split sampling have been used to examine alternative substantive ideas about the factorial structure of WAIS abilities. A variety of latent-structure path analysis (cf. LISREL) models have been used to study the multivariate dynamics underlying factor growth curves for age, year of testing, and education. Analytic and empirical studies of factorial invariance over age have been initiated and preliminary results recorted. Additional WAIS data (N=7,000) will be collected from known sources and added to the databank. A large scale comparison among the different Wechsler forms (WAIS, WB-I, WB-II, WAIS-R, and WISC-R) will provide an extensive and up-to-date scale equating for a much broader age and cohort range (N=28,000). The available longitudinal data (N=2,000) will be analyzed in terms of cross-lagged factor influences, by comparison to cross-sectional trends, and for subject attrition sampling biases. Latent structure aging trends will also be examined in the context of available data on clinical diagnostic categories (N=12,000), cross-cultural groups (N=5,000), and behavior genetic relative groups (N=3,000).
