Modeling the dynamic hypotheses of Gf-Gc theory using longitudinal life-span data

This research uses longitudinal data from the Wechsler Adult Intelligence S cale (WAIS) and linear structural equation models (e.g,, LISREL) in an eval uation of the structural, kinematic, and dynamic hypotheses of the "theory of fluid and crystallized intelligence." In a first set of analyses we use linear dynamic models in a formal evaluation of the growth and declines of abilities through latent growth and linear dynamic models. Our first result s indicate separate trends over age for different intellectual abilities in cluding broad knowledge, spatial reasoning, perceptual speed, and immediate memory. In a second set of analyses we extend these multivariate dynamic s tructural equation models to explore the age-based leading and lagging indi cators. These results indicate a complex system of relationships, with memo ry losses as an important leading indicator. In a third set of analyses we use confirmatory techniques to test specific aging hypotheses. These result s indicate support for both the "general memory loss" hypothesis and the "g eneral slowing" hypothesis, provide some support for the "investment theory " at the adult level, and also suggest a single "general" factor does not d escribe the complexity of cognitive aging. These result synthesize prior WA IS studies and provide methods for further research on the dynamics of the growth and decline of intellectual abilities across the adult life-span. (C ) 2001 Elsevier Science Inc. All rights reserved.