Longitudinal Evidence That Increases in Processing Speed and Working Memory Enhance Children's Reasoning

As children develop, their information-processing speed (PS) increases, and they retain more information in working memory (WM); these changes have been hypothesized to drive age-related improvements in reasoning and problem solving. For example, in Fry and Hale’s (1996) cascade model, developmental change in PS increases the functional capacity of WM, which in turn facilitates reasoning. Studies have shown that developmental increases in PS and WM during childhood and adolescence predict developmental improvements in inductive reasoning (Fry & Hale, 1996) and in accuracy on arithmetic word problems (Kail & Hall, 1999). However, although these findings are consistent with the cascade model, they provide relatively weak support because they are based on concurrent correlations derived from cross-sectional studies. The present work was designed to provide a stronger test of the cascade model using longitudinal evidence.