Connections and Disconnections: a Connectionist Account of Surface Dyslexia

The acquired reading disorder of surface dyslexia, in which lower-frequency words with atypical spelling-sound correspondences (e.g., PINT) become highly vulnerable to error, is presented in a framework based on interaction between distributed representations in a triangle of orthographic, phonological, and semantic domains. The framework suggests that low-frequency exception words are rather inefficiently processed in terms of orthographic-phonological constraints, because these words are neither sufficiently common to have much impact on learning in the network nor sufficiently consistent with the pronunciations of their orthographic neighbors to benefit from shared structure. For these words, then, the interaction between phonological and semantic representations may be especially important for settling on the correct pronunciation. It is therefore viewed as no coincidental association that all reported patients with marked surface dyslexia have also been profoundly anomic, suggesting reduced semanticphonological activation. The chapter summarizes the simulation of surface dyslexia in the computational model of reading developed by Plaut, McClelland, Seidenberg, and Patterson (1996), and presents new data from three surface alexic patients. The graded consistency effects in the patients’ reading performance are more compatible with the distributed connectionist framework than with dual-route models maintaining a strict dichotomy between regular and exception words.