A literature review and new data supporting an interactive account of letter-by-letter reading

We present a theoretical account of letter-by-letter reading (LBL) that reconciles discrepant findings associated with this form of acquired dyslexia. We claim that LBL reading is caused by a deficit that affects the normal activation of the orthographic representation of the stimulus. In spite of this lower-level deficit, the degraded orthographic information may be processed further, and lexical, semantic, and higher-order orthographic information may still influence the reading patterns of these patients. In support of our position, we present a review of 57 published cases of LBL reading in which we demonstrate that a peripheral deficit was evident in almost all of the patients and that, simultaneously, strong effects of lexical/semantic variables were observed on reading performance. We then go on to report findings from an empirical analysis of seven LBL readers in whom we document the joint effects of lexical variables (word frequency and imageability) and word length on naming latency. We argue that the reading performance of these patients reflects the residual functioning of the same interactive system that supported normal reading premorbidly.