Syntactic facilitation in agrammatic sentence production

Recently, proposals have been made to relate processing difficulties in aphasic language performance to limitations in resources for grammatical processing (Carpenter et al., 1994; Hagiwara, 1995; Kolk, 1995; Martin & Romani, 1994). Such proposals may account for a defining characteristic of agrammatic sentence production: reduced syntactic complexity. Syntactic structures that require deep hierarchical processing or reversals of canonical word order make demands exceeding limited resources. In the present study, we investigate the possibility of counteracting hypothesized resource limitations by increasing the availability of relatively complex sentences (i.e., datives and passives). The phenomenon of "syntactic priming" has been observed in a number of studies with healthy adults (e.g., Bock, 1986). With respect to Broca's aphasia, we hypothesized that increased availability of a syntactic structure, due to syntactic priming, results in a lesser demand on (limited) resources for sentence production. We elicited speech from 12 Broca's aphasics and 12 control subjects in three different conditions: spontaneous speech, picture description without priming, and picture description with priming. In addition, we varied instructions, in order to determine the role of strategies. The main findings were that (a) Brocas show stronger syntactic priming effects than controls; (b) the effects are automatic rather than strategic; and (c) in conditions with priming, Brocas produce relatively complex sentences (e.g., passives). We discuss these results in relation to capacity theories.