The malleability of agrammatic symptoms: A reply to Hesketh and Bishop

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Abstract
In their paper ‘Agrammatism and adaptation theory’, A. Hesketh and D. V. M. Bishop (Aphasiology, 1996, 10, p. 49–80), report a study on the language behaviour of a group of English-speaking aphasic patients. The purpose of this study was to replicate earlier findings reported for German and Dutch, showing that agrammatic speakers demonstrate particular kinds of variation in type of agrammatic output when the task demands are changed. Their conclusion is that the predictions made by adaptation theory are only partially supported. In this paper we discuss a number of methodological problems we have with the paper. In study 1, Hesketh and Bishop have used a methodology which is critically different from the ones employed in the studies they attempt to replicate. They had: (a) a different baseline, (b) a different elicitation procedure, and (c) a set of different response measures, not tailored to the predictions made by the theory. For these reasons their results must be regarded as inconclusive. Study 2 employed an elicitation procedure similar to one used previously; results are basically consistent with the predictions. The task used in Study 3 required the patient to select the right bound morpheme from a large set of morphological variants. Again the response measures were not appropriate, given the predictions of the theory. Furthermore, the test involved written materials, so that the presence of dyslexia in a number of patients could have influenced the results. Our general conclusion is that an appropriate replicational study in English for the findings on task variation is still called for.

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