Longitudinal evidence linking processing speed to the development of reasoning

Age‐related change in processing speed has been linked directly to increases in reasoning as well as indirectly via increases in the capacity of working memory (WM). Most of the evidence linking change in speed to reasoning has come from cross‐sectional research; in this article we present the findings from a 2½‐year longitudinal study of 277 6‐ to‐13‐year‐olds. On three occasions, speed of information processing was assessed with Visual Matching and Cross Out; WM was assessed with reading, listening, backward digit, alphabet, and operation span tasks; and nonverbal reasoning was assessed with Raven's progressive matrices. The results provided consistent evidence of direct links from processing speed to reasoning but inconsistent evidence for indirect links from speed to WM to reasoning. These findings suggest that variations in processing speed may constrain the development of reasoning, directly and perhaps indirectly. A video of this article can be viewed at: https://youtu.be/nc0VlFdi468 This longitudinal study examined the direct effects of age‐related change in processing speed on reasoning as well as indirect effects of processing speed mediated by working memory. The findings indicated that faster processing speed is associated longitudinally with improved reasoning but indirect influences via working memory were less consistent.