Abstract
The Seattle Longitudinal Study (SLS), initiated in 1956 by Dr. K. Warner Schaie, is one of the most comprehensive psychological research studies on cognitive aging. It aims to investigate various aspects of psychological development throughout adulthood, defined within the age range of 22 to 70. It focuses on individual differences and differential patterns of change for selected psychometric abilities from young adulthood to midlife to old age. It has determined the magnitude and relative importance of age changes in various cohorts in different skills [1].