Individual differences in working memory: A model testing and subgroup analysis of learning-disabled and skilled readers

Abstract

This experiment compares two models of working memory as means of explaining the variance in skilled and learning-disabled (LD) readers' comprehension performance. The contrasting models are tested as to whether short-term memory (STM) tasks operate independently, or serve as a subset of working memory (WM). Correlational and confirmatory factor analyses tested the alternative models. For Experiment 1, memory processes were inferred from performance on Sentence Span, Concurrent, and Preload tasks. Individual differences in the relationship between memory and reading performance were studied by subgrouping skilled and LD readers. The results support a process model in which LD readers have weaker WMs than skilled readers, not because of poor reading skills, but because they have less WM capacity available for performing reading and nonreading tasks. Experiment 2 extended the model to other measures of WM. Taken together, these studies support two primary conclusions: (a) WM reflects a number of independent processes that coalesce onto a single factor, independent of STM; and (b) reading comprehension and components of WM operate on a continuum of independence to dependence as reading becomes more skilled.