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

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.

KEYWORDS:

• Relative clauses
• eye tracking
• case
• number
• Relativized Minimality

Acknowledgments

We would like to express our gratitude to all participants, especially the individuals with aphasia for participating in this study. Moreover, we thank Romy Lassotta for her help with material preparation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. Due to case syncretism, das Mädchen can be either nominative or accusative case. Since the preceding relative pronoun is already unambiguously marked for accusative case, the embedded subject can only carry nominative case.

2. In German object-extracted wh-questions (i), the disambiguating case cue (i.e. nominative case on the determiner of the embedded subject) occurs later than the number cue in (ii) (i.e. subject-verb agreement between the verb and the embedded subject):

i.  Welche Vertreterin    hat   der Minister    kritisiert?

  Which delegate_{NOM/ACC, 3SG} has_SG  the minister_{NOM, 3SG} criticised?

  Which delegate has the minister criticised?

ii. Welche Vertreterin    haben die Minister    kritisiert?

  Which delegate_{NOM/ACC, 3SG} have_PL the ministers_{NOM, 3PL} criticised?

  Which delegate have the ministers criticised?

3. The complete list of target and filler sentences can be found in the supplementary material.

4. PLT was calculated by dividing the looks to the target picture by the sum of looks to the target and distractor pictures.

5. We thank an anonymous reviewer for raising this issue and pointing out the similarities between our results and language learning in children and adults.

6. Please note that due to aggregation across RoIs the time intervals for analysing the eye-movement data were 600 ms long. A more fine-grained analysis with time as a continuous variable would provide additional insight into the time course of processing case and number information in healthy speakers.

Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft [AD 408/1-1].