Activation of syntax in lexical production in healthy speakers and in aphasia

Theories of spoken word production agree that semantic and phonological representations are activated in spoken word production. There is less agreement concerning the role of syntax. In this study we investigated noun syntax activation in English bare noun naming, using mass and count nouns.

Fourteen healthy controls and 13 speakers with aphasia took part. Participants named mass and count nouns, and completed a related noun syntax judgement task. We analysed speakers' noun syntax knowledge when naming accurately, and when making errors in production.

Healthy speakers' noun syntax judgement was accurate for words they named correctly, but this did not correlate with naming accuracy. Speakers with aphasia varied in their noun syntax judgement, and this also did not correlate with naming accuracy. Healthy speakers' syntax for semantic errors was less accurate, as was that for speakers with aphasia. For phonological errors half the participants with aphasia could access syntax, half could not, indicating two types of phonological error. Individual differences were found in no responses. Finally, we found no effect of frequency for any of the above.

The lack of a relationship between syntax and naming accuracy suggests that syntax is available, but access is not obligatory. This finding supports theories incorporating non-obligatory syntactic processing, which is independent of phonological access. The semantic error data are best explained within such a theory where there is damage to phonological access and hence to independent syntax. For the aphasia group we identify two types of phonological error, one implicating syntax and phonology, and one implicating phonology only, again supporting independent access to these systems. Overall the data support a model within which syntax is independent of phonology, and activation of syntax operates flexibly dependent on task demands and integrity of other processing routines.