Treatment of sentence production deficits in aphasia: A linguistic-specific approach to wh-interrogative training and generalization

The present research examines the effects of a linguistic-specific treatment on acquisition and generalization of wh-interrogative structures in two aphasic subjects presenting with deficit patterns consistent with agrammatism. The underlying linguistic representation of sentence structures selected for treatment and generalization was considered based on aspects of Chomsky's (1981) Government Binding (GB) theory, and a linguistic-based, wh-movement treatment strategy was implemented. Using a single-subject multiple-baseline design across behaviours and subjects, the effects of treatment were explored by examining generalization patterns across wh question forms requiring wh-movement (movement of a direct object NP to COMP). Within question form generalization also was evaluated by examining formulation of untrained sentences of varied complexity—with complexity defined in terms of the number of phrasal nodes in the d-structure representation of sentences. Results indicated that for both subjects the heuristic strategy was successful in facilitating generalization from more to less complex interrogative sentences, and that for one subject generalization across wh forms was noted. These findings suggested that disrupted grammatical/linguistic processes and representations involved in translating d-structure to s-structure representations may explain some sentence production deficits seen in agrammatism, and support the use of wh-movement treatment for ameliorating this deficit pattern. Findings from this study highlight the utility of controlled single-subject experiments for examining the acquisition and generalization effects of treatment, not only for determining efficacious treatments for agrammatism, but also for providing insight into the relation between and among linguistic structures.