Semantic Influences On Parsing: Use of Thematic Role Information in Syntactic Ambiguity Resolution

Ferreira and Clifton (1986, Experiment 1) found that readers experienced equal difficulty with temporarily ambiguous reduced relatives clauses when the first noun was animate (e.g., "The defendant examined by the lawyer was . . .") and when it was inanimate and thus an unlikely Agent (e.g., "The evidence examined . . ."). This data pattern suggested that a verb′s semantic constraints do not affect initial syntactic ambiguity resolution. We repeated the experiment using: (1) inanimate noun/verb combinations that did not easily permit a main clause continuation, (2) a baseline condition with morphologically unambiguous verbs (e.g., "stolen"), (3) a homogeneous set of disambiguating prepositional phrases, and (4) a display in which all of the critical regions were presented on the same line of text. In two eye-movement experiments, animacy had immediate effects on ambiguity resolution: only animate nouns showed clear signs of difficulty. Post-hoc regression analyses revealed that what little processing difficulty readers had with the inanimate nouns varied with the semantic fit of individual noun/verb combinations: items with strong semantic fit showed no processing difficulty compared to unambiguous controls, whereas items with weak semantic fit showed a pattern of processing difficulty which was similar to Ferreira and Clifton (1986). The results are interpreted within the framework of an evidential (constraint-based) approach to ambiguity resolution. Analyses of reading times also suggested that the millisecond per character correction for region length is problematic, especially for small scoring regions. An alternative transformation is suggested.