Sixth International Conference on Spoken Language Processing
According to one widely held theory about language, the nature of processing for regular (and novel) vs. irregular transformations differs so fundamentally as to require two completely separate mechanisms. In the realm of the English past-tense, this theory has been most thoroughly described by Pinker . An alternative view, most recently developed by Joanisse & Seidenberg , 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.
Among various forms of empirical evidence pertinent to this theoretical debate, attention has recently turned to the performance of neurological patients with acquired language impairments. One popular paradigm assesses generation of the past-tense in a sentence frame preceded by the present tense of the same verb (┘coday I speak to my friend; yesterday I ___ to my friendíĘ). Previous evidence is reviewed and new evidence presented here for a double dissociation in this task, with some types of aphasic patients achieving 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. The semantic and phonological capabilities of patients with the two sides of the dissociation therefore become salient evidence in this debate. Additional features of the evidence, such as the nature of the patients' errors, seem to favour the constraint-satisfaction approach.
Bibliographic reference. Patterson, Karalyn / Ralph, Matthew A. Lambon / Bird, Helen / Hodges, John R. / McClelland, James L. (2000): "Normal and impaired processing in quasi-regular domains of language: the case of English past-tense verbs", In ICSLP-2000, vol.2, 15-19.