Role of inflectional regularity and semantic transparency in reading morphologically complex words: evidence from acquired dyslexia.

We report two patients with acquired phonological dyslexia who have great difficulty reading affixed words. Experiment 1 demonstrates that both patients' reading performance is influenced by the apparent morphological status of words by comparing the patients' reading of suffixed and pseudo-suffixed words. Experiment 2 was designed to examine reading performance of both regularly and irregularly inflected words. Experiment 3 examines the patients' reading of derivational forms with particular emphasis of the role of 'semantic transparency'. Experiment 4 tested both patients' reading of prefixed words. Finally, Experiment 5 examined performance on a lexical decision task using affixed words. These data support models in which regularly formed inflections and semantically transparent derived forms are subjected to decomposition during processing, whereas irregularly inflected forms and semantically opaque forms may be represented independently. Data are discussed with regard to current 'dual mechanism' models of morphological processing as well as connectionist perspectives, with particular emphasis of the types of data that will ultimately be necessary to arbitrate between the rival theories.