A time-based approach to agrammatic production.

A time-based approach to agrammatic speech is presented. The paper consists of three parts. In the first part, the literature which deals with agrammatic comprehension as a problem of disrupted timing, that is, as a slow-down of syntactic computation and/or a rapid decay of the results of syntactic processing, is reviewed. In a second part, the hypothesis that similar timing problems cause difficulties in production as well is discussed. Two possible ways in which this can happen are described. First, slow down or rapid decay can lead to desynchronization within the process of syntactic tree formation. Second, a slow down of syntactic processing can cause asynchrony between the production of a syntactic slot and the retrieval of the proper grammatical morpheme from the mental lexicon. This hypothesis predicts that morphemes which are dependent on a relatively complex part of the syntactic tree will elicit relatively many errors. Results from the literature which seem to confirm this prediction are discussed. In the third part of the paper, the possible ways in which a patient can adapt to the reduced temporal window that would result from a timing deficit are discussed. Message simplification will reduce the size of the required temporal window and will therefore have a beneficial effect on the error rate. Restart of the computational process will profit from previously reached activation levels so that synchrony is easier to reach and error rate is reduced. Empirical work which appears to support these hypotheses is reviewed.