Producing and inflecting verbs with different argument structure: Evidence from Greek aphasic speakers

Abstract

Background: Verb argument structure affects language production in aphasia. Unaccusative verbs have been found to be more difficult than transitive or unergative verbs across languages. Transitivity is also a factor with variable influence across aphasia types. Verb inflection production, and in particular tense and aspect, has been found to be vulnerable in aphasia, too. These domains have been studied independently of each other, and their potential interaction has been scarcely addressed.Aims: The present study explores the effects of argument structure and past tense on verb production in Greek aphasia. Additionally, we address the question of the interrelation between inflection and verb and argument structure production.Methods & Procedures: Two tasks were administered to 10 aphasic participants (six anomic, two Wernicke’s and two agrammatic Broca’s). The first task (sentence elicitation) consisted of video presentation and description of the video. The second task (tensed sentence elicitation) consisted of presentation of a video preceded by an adverbial prompting for a specific inflection marking. Participants had to produce a sentence with a verb in a specific past form. In both tasks, three verb classes were tested (unergative, unaccusative and transitive verbs with one object) with six items each.Outcomes & Results: The sentence elicitation task showed that unaccusative verbs are the most difficult class for the aphasic participants whose predominant error was the production of +agentive verbs instead of unaccusatives. The tensed sentence elicitation task showed that while for most patients there was no effect of inflection on verb and verb argument production, a decremental effect was noticed for an agrammatic participant.Conclusions: We suggest that +/− agentivity ranks above transitivity concerning verb production. To account for the unaccusativity effect, we provide a novel account based on the distinction between thematic and aspectual dimension and argue that unaccusative verbs are more difficult to produce, because they involve a mismatch between the two dimensions of argument structure (thematic and aspectual dimension). Concerning the effect of past tense on verb production we show that such pattern is possible but it does not emerge at the group level. Finally, our group data do not suggest any interrelation between inflection, on the one hand, and verb and argument structure production, on the other hand.