The Roles of Thematic Knowledge in Sentence Comprehension

People possess a great deal of knowledge concerning what commonly happens in various types of events. This knowledge, specifically with respect to event participants and their relations within an event (thematic knowledge), is an important component of how people understand language. A number of studies have shown a rapid influence of thematic knowledge during moment-to-moment sentence processing, in both investigations of lexical processing in sentential contexts, and temporary syntactic ambiguity resolution. The main goal of this dissertation is to further our understanding about the roles of thematic knowledge during sentence processing and sentence understanding by examining two critical unresolved issues. Chapter 2 investigated whether manipulation of thematic knowledge can lead to processing disruption in sentences that are otherwise assumed to be free of processing difficulty. That is, I investigated whether simple sentences can be made more difficult. This issue is particularly important for adjudicating among two major theories of sentence comprehension, two-stage and constraint-based theories. I found that main clause sentences could be made more difficult by manipulating thematic fit of the initial noun phrase, as in The host invited versus The guest invited. Because the influence of thematic fit was found at the earliest point at which it could be expected, the results strongly support constraint-based models. Chapter 3 investigated how thematic knowledge affects the construction of sentential meaning representations, and how misinterpretations can occur during that process. Specifically, the study evaluated several possibilities regarding how misanalyses of thematic roles might occur in full passive sentences that varied in plausibility. Participants’ understanding was determined by asking them to recall the agent or patient of each target sentence. The novel aspects of this study involved in-depth analyses of the types of errors that participants make, and using ERPs to investigate on-line processing differences. A major result was that the N400 ERP component was smaller for trials on which participants made an error versus when they responded correctly, indicating that errors occurred when readers were not sensitive to thematic implausibility. In summary, the studies reported in this dissertation provide novel and important theoretical insights into thematic role processing during sentence comprehension