Modeling the influence of thematic fit (and other constraints) in on-line sentence comprehension

The time-course with which readers use event-specific world knowledge (thematic fit) to resolve structural ambiguity was explored through experiments and implementation of constraint-based and two-stage models. In a norming study, subjects completed fragments that ended in the ambiguous region of a reduced relative clause (The crook arrested/by/the/detective). Completion proportions up to and including the were influenced by thematic fit. The results were simulated using a competition model in which independently quantified syntactic and semantic constraints simultaneously influenced interpretation. Predictions were then generated for a self-paced reading task using model parameter values established by the off-line simulations. The pattern of reading times matched the predictions of the constraint-based version of the model but differed substantially from a one-region delay garden-path version. In addition, garden-path model with a very short delay simulated the data better than the one-region delay model, but not as closely as the constraint-based version. The experiment and modeling illustrate that thematic fit is computed and used immediately in on-line sentence comprehension. Furthermore, the modeling highlighted the difficulty of interpreting sentence comprehension experiments without both quantifying the relevant constraints and implementing the mechanisms involved. (C) 1998 Academic Press.