Bridging gaps in common ground: Speakers design their gestures for their listeners.

Communication is shaped both by what we are trying to say and by whom we are saying it to. We examined whether and how shared information influences the gestures speakers produce along with their speech. Unlike prior work examining effects of common ground on speech and gesture, we examined a situation in which some speakers have the same amount of mutually shared experience with their listener but the relevance of the information from shared experience is different for listeners in different conditions. Additionally, speakers and listeners in all conditions shared a visual perspective. Speakers and listeners solved a version of the Tower of Hanoi task together. Speakers then solved a second version of the task without the listener present with the manner of disk movement manipulated; the manner was either the same as or different from the version that had been solved with the listener present. Thus, speakers' knowledge of the relevance of shared knowledge was manipulated. We measured the content of speech along with the physical form and content of the accompanying hand gesture. Although speakers did not modulate their spoken language, speakers who knew their listeners had not previously experienced the appropriate manner of completion gestured higher in space, highlighting manner information, but without altering the physical gesture trajectory. Thus, gesture can be sensitive to the knowledge of listeners even when speech is not. Speakers' gestures can play an independent role in reflecting common ground between speakers and listeners, perhaps by simultaneously incorporating both speaker and listener perspectives. (PsycINFO Database Record (c) 2016 APA, all rights reserved).