This proposal covers the data analysis and reporting stage for a series of sequential studies of Age Changes and Generational differences in Cognitive Abilities throughout adulthood. Data were collected also on Health History and Environmental Correlates of change in intellectual function, as well as bearing upon the issues of Monetary Incentive in volunteering, shifting from sampling without replacement to sampling with replacement designs, experimental inability and on the "aging" of measurement instruments in the study of cognitive behavior. Data include a sample of 500 Ss (22 to 70 years of age) studied in 1956 and partially retested in 1963, 1970 and 1977. A second sample of 1000 Ss was first tested in 1963 and partially retested in 1970 and 1977. A third sample of 701 Ss first tested in 1970 was also partially retested in 1977, and there is a new random sample drawn from the parent population on a sampling with replacement basis. Measures include Thurstone's Primary Mental Abilities Test, Schaie's Test of Behavioral Rigidity and health history data throughout, as well as data on a Life Complexity Scale, selected measures from the ETS reference Kit and 16 PF for some of the more recent data collections. The analysis will yield data on series of seven-year, fourteen-year and twenty-one year Longitudinal Studies of change in cognitive behavior within cohorts, as well as data on generational differences over three seven year time intervals. In addition individual patterns of maintenance and decline of intellectual abilities in adulthood will be identified in relation to salient health and environmental variables and further contributions will be made to Research Methodology in the study of adult development.