New evidence for morphological errors in deep dyslexia

Morphological errors in reading aloud (e.g., sexist → sexy) are a central feature of the symptom-complex known as deep dyslexia, and have historically been viewed as evidence that representations at some level of the reading system are morphologically structured. However, it has been proposed ( Funnell, 1987) that morphological errors in deep dyslexia are not morphological in nature but are actually a type of visual error that arises when a target word that cannot be read aloud (by virtue of its low imageability and/or frequency) is modified to form a visually similar word that can be read aloud (by virtue of its higher imageability and/or frequency). In the work reported here, the deep dyslexic patient DE read aloud lists of genuinely suffixed words (e.g., killer), pseudosuffixed words (e.g., corner), and words with non-morphological embeddings (e.g., cornea). Results revealed that the morphological status of a word had a significant influence on the production of stem errors (i.e., errors that include the stem or pseudostem of the target): genuinely suffixed words yielded more stem errors than pseudosuffixed words or words with non-morphological embeddings. This effect of morphological status could not be attributed to the relative levels of target and stem imageability and/or frequency. We argue that this pattern of data indicates that apparent morphological errors in deep dyslexic reading are genuinely morphological, and discuss the implications of these errors for theories of deep dyslexia.