Verbal Coding Deficits in Learning-Disabled Readers: A Multiple Stage Model

This article reviews some selected literature, drawn from the last 10 years, suggesting that learning-disabled (LD) readers have functionally independent visual and verbal coding systems. The review focuses on studies where it has been shown that learning-disabled readers fail to effectively establish visual and verbal coding interconnections, which in turn impairs their episodic memory for visual information. It is hypothesized that this faulty intereonnection is manifested by verbal codes failing to adequately provide an "additive" component to enhance the recall of visual information. The article reviews some data supporting this hypothesis, as well as extending the hypothesis by suggesting that a deficient lexical system may contribute to disabled readers' independent coding operations on a picture-naming task. The research is organized within a tentative model which assumes that there are at least three distinct information-processing stages (modality-specific, semantic, and lexical processing) that play an important role in disabled readers' processing of visual information.