What do you know? ERP evidence for immediate use of common ground during online reference resolution

Recent evidence on the time-course of conversational perspective taking is mixed. Some results suggest that listeners rapidly incorporate an interlocutor's knowledge during comprehension, while other findings suggest that listeners initially interpret language egocentrically. A key finding in support of the egocentric view comes from visual-world eye-tracking studies - listeners systematically look at potential referents that are known to them but unknown to the speaker. An alternative explanation is that eye movements might be driven by attentional processes that are unrelated to referent identification. To address this question, we assessed the time-course of perspective taking using event-related potentials (ERP). Participants were instructed to select a referent from a display of four animals (e.g., "Click on the brontosaurus with the boots") by a speaker who could only see three of the animals. A competitor (e.g., a brontosaurus with a purse) was either mutually visible, visible only to the listener, or absent from the display. Results showed that only the mutually visible competitor elicited an ERP signature of referential ambiguity. Critically, ERPs exhibited no evidence of referential confusion when the listener had privileged access to the competitor. Contra the egocentric hypothesis, this pattern of results indicates that listeners did not consider privileged competitors to be candidates for reference. These findings are consistent with theories of language processing that allow socio-pragmatic information to rapidly influence online language comprehension. The results also suggest that eye-tracking evidence in studies of online reference resolution may include distraction effects driven by privileged competitors and highlight the importance of using multiple measures to investigate perspective use.