INDIVIDUAL-DIFFERENCES IN WORKING-MEMORY - A MODEL TESTING AND SUBGROUP ANALYSIS OF LEARNING-DISABLED AND SKILLED READERS

This experiment compares two models of working memory as means of expl aining the variance in skilled and learning-disabled (LD) readers' com prehension performance. The contrasting models are tested as to whethe r short-term memory (STM) tasks operate independently, or serve as a s ubset of working memory (WM). Correlational and confirmatory factor an alyses tested the alternative models. For Experiment 1, memory process es were inferred from performance on Sentence Span, Concurrent, and Pr eload tasks. Individual differences in the relationship between memory and reading performance were studied by subgrouping skilled and LD re aders. The results support a process model in which LD readers have we aker WMs than skilled readers, not because of poor reading skills, but because they have less WM capacity available for performing reading a nd 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.