Created in 1978 to obtain normative data for the Schaie-Thurston Adult Mental Abilities Test (STAMAT). From 1994 to 2003 it was extended under the guiding principle that cognitive aging is a largely contextual phenomenon. Individual differences in abilities and change in those abilities over adulthood are associated not only with cognitive mechanisms, but with sociodemographic phenomena such as birth cohort, or gender, and within-individual characteristics, including health, affect, self-efficacy, personality, and other variables that impact health. This principle is reflected in the testing measures added to the original panel. Besides the original ability measures used by Schaie, the Life Complexity Inventory, has been included in all testing.