This study experimentally manipulates common ground (the knowledge, beliefs and assumptions interlocutors mutually share [6]) and measures the effect on speakers’ use of interactive gestures to mark common ground. The data consist of narratives based on a video of which selected scenes were known to both speaker and addressee (common ground condition) or to only the speaker (no common ground condition). The analysis focuses on those interactive gestures that have been described in the literature as ‘shared information gestures’ [4]. The findings provide experimental evidence that certain interactive gestures are indeed linked to common ground. Further, they show that speakers seem to employ at least two different forms of shared knowledge gestures. This difference in form appears to be linked to speakers’ use of gesture in the grounding process, as addressees provided feedback more frequently in response to one of the gesture types.