Definite reference and mutual knowledge: process models of common ground in comprehension

What role does mutual knowledge play in the comprehension process? We compare two answers to this question for the comprehension of definite reference. The Restricted Search hypothesis assumes that addressees rely on the principle of optimal design and understand definite reference by restricting the search for referents to entities in common ground. The Unrestricted Search hypothesis assumes that the search for referents is not restricted to entities in common ground. Only the Unrestricted Search hypothesis predicts that entities that are not in common ground would interfere with comprehension of definite reference. Experiment 1 reveals such interference in increased errors and verification latencies during the resolution of pronouns. Experiment 2 demonstrates the interference by tracking the addressee's eye movements during the comprehension of demonstrative reference. We discuss alternative models of comprehension that could account for the results, and we describe the role that common ground plays in each model. We propose a Perspective Adjustment model that assumes a search for referents that is independent of common ground, coupled with a monitoring process that detects violations of common ground and adjusts the interpretation. This model assumes a role for common ground only when a correction is needed. We challenge both the assumption that addressees follow the principle of optimal design and the assumption that the principle is optimal