EXAMINING THE EMPIRICAL AND LINGUISTIC BASES OF CURRENT THEORIES OF AGRAMMATISM

This paper, which is organized into five sections, critically examines the empirical support and linguistic assumptions underlying several c urrent accounts of language disturbances in Broca's aphasia. In the fi rst section, following a discussion of the use of signal detection met hodologies in investigating grammatical sensitivity, the reliability o f results from two studies that suggest that Broca's aphasic patients are differentially sensitive to grammatical constraints is examined. I t is concluded that in some cases, claims of intact sensitivity are no t supported. The second section examines the empirical support for the hypothesis that agrammatic patients are unable to compute syntactic d ependency relationships because of slowed lexical processing. It is ar gued that the statistical treatment of the data and interpretive probl ems associated with the lexical decision paradigm undermine this hypot hesis. In the third section, some of the linguistic assumptions underl ying criticisms of chain-disruption hypotheses are examined. It is con cluded that these criticisms are based on arguable linguistic assumpti ons. In the fourth section, it is argued that the linguistic and empir ical support for both earlier and revised versions of Grodzinsky's def ault interpretive strategy is lacking. Methodological and conceptual s hortcomings arising from this proposal are also discussed. In the fina l section, potential relationships between disordered language and cur rently developing models of normal language processing are discussed. (C) 1995 Academic Press, Inc.