We describe a study that investigated how a shared interactive tabletop (DiamondTouch) can be designed to provide new opportunities for supporting collaborative decision-making. Small groups of users were required to work together using the table by selecting and placing digital images into a calendar template and justifying their choices to one-to-another. A variety of novel fingertip interactions were developed to support simultaneous, shared direct manipulation at the tabletop. Our findings showed that new forms of distributed interactions emerged while the groups worked together. Alongside conventional methods of communication, group members talked to each other with their fingers. The role of this finger talk served a number of functions, including the support of turn-taking, the emphasis on and substitution for speech acts and the encouragement of balanced contributions from all participants. We discuss how finger talk is integral to the collaborative use of the interactive tabletop surface.