Spontaneous perspective-taking in real-time language comprehension: evidence from eye-movements and grain of coordination.

Linguistic communication requires interlocutors to consider differences in each other's knowledge (perspective-taking). However, perspective-taking might either be spontaneous or strategic. We monitored listeners' eye movements in a referential communication task. A virtual speaker gave temporally ambiguous instructions with scalar adjectives ("big" in "big cubic block"). Scalar adjectives assume a contrasting object (a small cubic block). We manipulated whether the contrasting object (a small triangle) for a competitor object (a big triangle) was in common ground (visible to both speaker and listener) or was occluded so it was in the listener's privileged ground, in which case perspective-taking would allow earlier reference-resolution. We used a complex visual context with multiple objects, making strategic perspective-taking unlikely when all objects are in the listener's referential domain. A turn-taking, puzzle-solving task manipulated whether participants could anticipate a more restricted referential domain. Pieces were either confined to a small area (requiring fine-grained coordination) or distributed across spatially distinct regions (requiring only coarse-grained coordination). Results strongly supported spontaneous perspective-taking: Although comprehension was less time-locked in the coarse-grained condition, participants in both conditions used perspective information to identify the target referent earlier when the competitor contrast was in privileged ground, even when participants believed instructions were computer-generated.