  Innovation is the driving force of human progress. Recent urn models
reproduce well the dynamics through which the discovery of a novelty may
trigger further ones, in an expanding space of opportunities, but neglect the
effects of social interactions. Here we focus on the mechanisms of collective
exploration and we propose a model in which many urns, representing different
explorers, are coupled through the links of a social network and exploit
opportunities coming from their contacts. We study different network structures
showing, both analytically and numerically, that the pace of discovery of an
explorer depends on its centrality in the social network. Our model sheds light
on the role that social structures play in discovery processes.
