What matters in processing German object relative clauses in aphasia – timing or morpho-syntactic cues?

Abstract

ABSTRACT Background It is a well-established finding that individuals with aphasia have difficulties in using morpho-syntactic cues to determine the meaning of non-canonical sentences, such as object relative clauses (ORCs). While non-brain-damaged speakers can process ORCs disambiguated through unambiguous case marking more easily than number marking (i.e. subject-verb agreement), there is still much debate concerning the varying impact of case and number cues on sentence processing in aphasia. Aims The objective of the present study is to investigate the use of case and number marking as cues to sentence interpretation and to test the predictions of the Relativized Minimality approach. Within this account, dissimilarity in the number specification of the subject and object is assumed to facilitate ORC processing in aphasia, while case is not. Methods & Procedures Combining the visual-world eye-tracking methodology with an auditory referent-identification task, we measured offline and online sentence processing in German-speaking individuals with aphasia and in a group of control participants. ORCs were disambiguated through case or number marking, whereby case occurred at different points of disambiguation: case marking at (1) the relative pronoun, (2) the following noun phrase, or (3) number marking on the sentence-final verb. Thereby, we were able to control for number dissimilarity of the subject and object in ORCs, with number specification being similar in case-marked ORCs and dissimilar in number-marked ORCs. Outcome & Results We found that both participant groups exhibit a general processing advantage for case- over number-disambiguated ORCs. Moreover, case-marked ORCs disambiguated at different positions within the sentence were processed similarly in term of accuracy, reaction times or online processing speed. Conclusions These results support the assumption that case marking can be used more successfully to derive sentence meaning as compared to number marking – regardless of the timing of disambiguation. Future research is needed to further disentangle the status of case and number in the computation of Minimality.