My primary research interests concern the cognitive and social dimensions of learning through human interaction. I conduct both basic, theory-driven research, as well as practice-oriented, design research, and strongly believe in the need of a multidisciplinary, multi-method approach to the study of learning that requires close collaboration with experts from different fields. My approach to the study of learning combines quantitative as well as qualitative analyses. I believe that the combination of rigorous experimental research with qualitative methods, such as micro-genetic or dialogue analyses, can be a particular powerful combination to provide valuable insights in the conditions for and the processes of learning. Topic-wise, my research interests are in collaborative learning, argumentation, teacher support of learning dialogues, instruction for conceptual change, teacher-teacher dialogues, social networks in education, and computer-mediated communication.