An investigation of the interaction between thematic and phrasal structure in nonfluent agrammatic subjects

Garrett (1982) developed a model of normal sentence production which has been used in the description of aphasic language (Schwartz, 1987). This study investigated the effects of the thematic representation specified at the functional level on the complexity of the phrases produced at the positional level. A group of 14 nonfluent, agrammatic subjects were compared to 20 normal controls in their production of the story of Cinderella. The agrammatic subjects produced fewer argument structures than the normal control subjects. Their phrasal realization of the arguments, however, was not qualitatively different from that of the normal subjects. In both cases, with an increase in the number of arguments, there was a concurrent increase in the mean complexity of the phrases used to realize those arguments and in the total phrasal complexity of the utterances. The complexity of noun phrases differed according to the thematic roles expressed; this seemed to be a consequence of their different locations in the sentence. Preverbal noun phrases were much less complex than postverbal noun phrases. There was no evidence to suggest that there was a trade-off between the production of thematic structure and subsequent phrasal production. Neither was there evidence to suggest that production differed according to whether the phrase was an argument of the verb or a nonargument. The complexity of a phrase was determined by the type of information it conveyed.