A CAPACITY APPROACH TO SYNTACTIC COMPREHENSION DISORDERS - MAKING NORMAL ADULTS PERFORM LIKE APHASIC PATIENTS

This paper presents a theory of syntactic comprehension disorders in a phasic patients. In line with some recent proposals, the current theor y assumes that aphasic patients still possess the structural (syntacti c) and procedural knowledge necessary to perform syntactic analysis. T his paper, however, postulates that patients' comprehension deficits o riginate, at least in part, from reductions in working memory capacity for language. Based on a recently developed theory of capacity constr aints in normal language comprehension (Just & Carpenter, 1992), the t heory explains how reductions in working memory capacity can lead to t he pattern of comprehension breakdown in aphasics, which can be charac terised as a conjoint function of the patient's severity level and the structural complexity of the sentence. As supporting evidence for the theory, we report two ''simulation'' experiments in which we increase d the computational demands on normal adults of varying working memory capacities and thereby induced in them the interaction of ''severity' ' by complexity usually observed among aphasic patients.