Acknowledgement. Contributors. Introduction: what do you mean by 'collaborative learning'? (P. Dillenbourg). Learning together: understanding the processes of computer-based collaborative learning (K. Littleton, P. Hakkinen). The role of grounding in collaborative learning tasks (M. Baker et al.). What is "multi" in multi-agent learning? (G. Weiss, P. Dillenbourg). Comparing human-human and robot-robot interactions (R. Joiner et al.). Learning by explaining to oneself and to others (R. Ploetzner et al.). Knowledge transformations in agents and interactions: a comparison of machine learning and dialogue operators (E. Mephu Nguifo et al.). Can analytic models support learning in groups? (H.U. Hoppe, R. Ploetzner). Using telematics for collaborative knowledge construction (T. Hansen et al.). The productive agency that drives collaborative learning (D. Schwatrtz). References. Index.