Surface Dyslexia

Abstract

Two cases of surface dyslexia are described. In this disorder, irregular words such as broad or steak are less likely to be read aloud correctly than regularly-spelled words like breed or steam; and when irregular words are misread the incorrect response is often a regularisation (reading broad as “brode” and steak as “steek, for example). When reading comprehension was tested, homophones were often confused with each other: for example, soar was understood as an instrument for cutting, and route was understood as being part of a tree. Spelling was also impaired, with the majority of spelling errors being phonologically correct: for example, “search” was spelled surch. “Orthographic” errors in reading aloud (omitting, altering, adding or transposing letters) were also noted. These errors were not due to defects at elementary levels of visual processing. One of our cases was a developmental dyslexic, and the other was an acquired dyslexic. The close similarity of their reading and spelling performance supports the view that surface dyslexia can cccur both as a developmental and as an acquired dyslexia. A theoretical interpretation of surface dyslexia within the framework of the logogen model (including a grapheme-phoneme correspondence system for reading non-words) was offered: defects within the input logogen system, and in communication from that system to semantics, were postulated as responsible for most of the symptoms of surface dyslexia.