The independence of phonological and orthographic lexical forms: Evidence from aphasia

WMA suffers from damage to the semantic component of the lexical semantic system and from damage to sublexical phonology-orthography and orthography-phonology conversion procedures. His performance on picture naming tasks that require two consecutive responses was used to explore issues concerning the relations between the phonological and orthographic components of the lexical system. Responses to tasks requiring responses in different modalities (one oral and one written) often resulted in lexically ''inconsistent'' responses. For example, to a picture representing pliers, WMA said ''pincers,'' but wrote saw,; and, to a picture representing peppers, he wrote tomato but said ''artichoke.'' By contrast, inconsistent responses never occurred in tasks that required two consecutive responses in the same modality (oral or written). In these tasks, WMA always produced the same (correct or incorrect) word twice. These results rule out the hypothesis that phonological mediation is necessary for writing, and suggest instead that orthographic word forms are autonomous from phonological forms, and that they are activated directly from lexical semantic information. However, the results do not allow us to distinguish between a weak version of the orthographic autonomy hypothesis-that there are direct connections between phonological and orthographic forms, which are impaired in WMA-and a strong version of the same hypothesis-that phonological and orthographic word forms are completely autonomous but that the selection of a word form for output in a given modality can be constrained by sublexical conversion mechanisms, which are impaired in WMA.