Chapter 5. If you don’t already know, I’m certainly not going to show you!

The present study aimed to determine if variations in a speaker’s motivation to communicate influence the frequency or size of the gestures the speaker produces. We observed the gestures produced by speakers as they gave route directions to a listener who they believed would use the information either to cooperate with them in a later game, compete with them, or merely play simultaneously. Gesture rates were not affected. However, speakers produced a higher proportion of gestures that were large in size when they expected their listener to cooperate with them than when they expected their listener to compete with them. These findings suggest that gestures are shaped in part by speakers’ desire to communicate information clearly to their listeners.