A test of the cascade model in the elderly

Abstract

The cascade theory (Fry & Hale, 1996) posits that developmental changes in perceptual speed in childhood increase the capacity of working memory, which increases fluid reasoning performance. Support for this theory is available from cross-sectional and longitudinal research. Similar cognitive changes have been reported in elderly adults as decreasing speed and working memory capacity with age result in decreasing fluid reasoning (Salthouse, 1991). Thus, this study investigated whether the cascade theory could explain age-related deterioration in fluid reasoning by replicating Kail’s (2007) longitudinal study in elderly adults. One hundred and twenty one elderly people completed measures of perceptual speed, working memory and fluid reasoning at Time 1. Eighteen-months later, participants were retested on fluid reasoning. Results provided partial support for the cascade theory, confirming a significant path from age to fluid reasoning via perceptual speed and working memory. However, both cross-sectional and longitudinal models also included a significant direct path from perceptual speed to fluid reasoning, inconsistent with the cascade model. Therefore, it is possible that the cascade model does not explain aged-related changes in fluid reasoning in the same way that it explains developmental change in fluid reasoning in children.