Sidestepping garden paths: Assessing the contributions of syntax, semantics and plausibility in resolving ambiguities

A central issue in the study of sentence processing is the manner in which various sources of information are used in resolving structural ambiguities. According to one proposal, the garden path model (e.g. Frazier & Rayner, 1982), perceivers are initially guided by strategies based solely on the structural properties of sentences. Another class of models, constraint satisfaction models, emphasise the influence of lexical properties in decisions among the alternative analyses of an ambiguous sentence fragment (e.g. Tanenhaus, Garnsey, & Boland, 1991). In this paper, we explore the prediction of an alternative model, the referential theory (e.g. Grain & Steedman, 1985). The referential theory maintains that the relative complexity of discourse representations plays a key role in determining the perceiver's immediate parsing preferences. We present four experiments designed to weigh the influence of semantic/referential complexity and general world knowledge in the on-line resolution of two kinds of structurally ambiguous sentences. In each experiment, we examined pairs of sentences that wereidentical except for the alternation between the definite determiner THE and the focus operator ONLY. Two techniques were used to assess ambiguity resolution: word-by-word reading and eye movement recording. The results indicate that semantic/referential principles are applied immediately in on-line ambiguity resolution and that these principles pre-empt general world knowledge. The use of world knowledge was found to depend on working memory capacity, whereas the resolution of ambiguity by means of semantic/referential principles appeared to be independent of memory resource. Taken together, the findings are interpreted as support for the referential theory of ambiguity resolution.