Alumni events and homecomings provide opportunities to reconnect and reminiscence with old friends and colleagues, i.e., they aim to reinforce connections between community members. Although these events explicitly foster social interaction, the first step in engaging with others can still be difficult. To help "break the ice", we have built USIAlumni Faces, a 'yearbook' application running on a public display that is operated via a gesture interface. We deployed USIAlumni Faces at a large university alumni event, which gave us the opportunity to observe and understand learning techniques for gesture interfaces and their role in supporting the emergence of social interaction in public spaces. We found that gesture-based interfaces support the natural diffusion of interaction patterns in public spaces through the observe-and-learn model, and that sensory-motor patterns can aid social interaction in public, as they act as conversation starters between both strangers and acquaintances. © 2011 Springer-Verlag.