Primary Mental AbilitiesSeattle Longitudinal Study (Schaie 1983)
o Primary Mental Abilities; Crystallized abilities, visualization abilities, verbal memory, perceptual and psychomotor speed. TPMAT: Verbal meaning, reasoning, number, Word Fluency; STAMA: Verbal ability; Letter & Word Series; Spatial & Object & Alphanumeric Rotation, number, word fluency; Mattis Dementia Rating Scale, Trails A& B.
This study followed a series of community-based cohorts enrolled in a large HMO. Sample sizes for individual cohorts were between 500-997. The main findings were that individual cognitive abilities did not change much before age 60, with the exception of verbal fluency. Beyond that age, there continued to be decline in several areas of intellectual functioning. Owing to attrition, the study did not have large enough samples with which to detect small cognitive declines in younger age groups. Few individual participants were followed for longer than 5 yrs.
Bosworth HB, Schaie KW, Willis SL. (1999). Cognitive and sociodemographic risk factors for mortality in the Seattle Longitudinal Study.
Schaie KW (1994). The course of adult intellectual development.