We present findings from an empirical study of how groups of eight users collaborate on a decision-making task around an interactive tabletop. To our knowledge, this is the first study to examine co-located collaboration in larger groups (of 8-12 users) seated around a large-scale high-resolution multi-touch horizontal display. Our findings shed light on: 1) the effect of collaboration patterns of larger groups on equity of participation; 2) the role of participants' position around the tabletop in forming collaborations; and 3) the mechanisms, which facilitate coordination and collaboration in larger group interacting around large-scale tabletops; We also contribute computational methods that leverage image processing to analyze interaction around large-scale tabletops. Finally, we discuss implications for the design of large-scale tabletop systems for supporting co-located collaboration in larger groups.
