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Normal and Impaired Processing in Quasi-Regular Domains of Lanuage: The Case Of English Past-Tense Verbs
Patterson, K., Lambon Ralph, M. A., Bird, H., Hodges, J R., McClelland, J.L.
Proceedings of the 6th International Conference on Spoken Language Processing, Vol 2, Beijing, China, 15-19
Year of publication:
The relationship between present- and past-tense verbs in English can be described as quasi-regular, because the majority of verbs are transformed to past tense by adding -ed (e.g., talkÆ talked), while the remainder form their past tenses in an atypical way (e.g., speakÆ spoke; thinkÆ thought). According to one widely held theory, the nature of processing for regular vs. irregular transformations differs so fundamentally as to require two completely separate mechanisms. An alternative view proposes that all types of past-tense transformation are achieved by a single distributed, constraint-satisfaction process recruiting activation of the phonological and semantic representations of words. Pertinent to this theoretical debate is a double dissociation in the performance of patients with acquired language impairment: some types of aphasic patients achieve greater success on regular and novel verbs whereas others show an advantage for irregular verbs. Although the dual-mechanism theory predicts this double dissociation, such a pattern of results can also be well explained by a single constraint-satisfaction process. The crucial proposal here is that disruption to semantic representations has a disproportionate impact on the processing of irregular forms, and that disruption to phonological processing is more detrimental to success with regular forms. This paper briefly reviews recent evidence on both sides of the dissociation and discusses predictions for languages other than English in quasi-regular domains of language processing.