Real-time production of arguments and adjuncts in normal and agrammatic speakers

Abstract

Two eyetracking experiments examined the real-time production of verb arguments and adjuncts in healthy and agrammatic aphasic speakers. Verb argument structure has been suggested to play an important role during grammatical encoding (Bock & Levelt, 1994) and in speech deficits of agrammatic aphasic speakers (Thompson, 2003). However, little is known about how adjuncts are processed during sentence production. The present experiments measured eye movements while speakers were producing sentences with a goal argument (e.g., the mother is applying lotion to the baby ) and a beneficiary adjunct phrase (e.g., the mother is choosing lotion for the baby ) using a set of computer-displayed written words. Results showed that the sentence production system experiences greater processing cost for producing adjuncts than verb arguments and this distinction is preserved even after brain-damage. In Experiment 1, healthy young speakers showed greater gaze durations and gaze shifts for adjuncts as compared to arguments. The same patterns were found in agrammatic and older speakers in Experiment 2. Interestingly, the three groups of speakers showed different time courses for encoding adjuncts: young speakers showed greater processing cost for adjuncts during speech, consistent with incremental production (Kempen & Hoenkamp, 1987). Older speakers showed this difference both before speech onset and during speech, while aphasic speakers appeared to preplan adjuncts before speech onset. These findings suggest that the degree of incrementality may be affected by speakers’ linguistic capacity.

Keywords:

• Adjuncts
• Verb arguments
• Agrammatism
• Sentence production
• Eyetracking

Acknowledgements

The authors want to thank Dr. Michael W. Dickey, Kyla Garibaldi, Keli Rulf and other members of the Aphasia & Neurolinguistics Research Laboratory for their comments and help with this study. We also thank the audience at CUNY 2008 on Human Sentence Processing and the fifth international language production workshop for their feedback. Special thanks go to the aphasic patients who participated in the study. This research was supported by the NIH R01-DC01948 (C.K. Thompson).