Running head: REDUNDANCY AND POLARITY IN KNOWLEDGE BUILDING 1 Collaborative Knowledge Building with Wikis: The Impact of Redundancy and Polarity. Johannes Moskaliuk and Joachim Kimmerle University of Tuebingen, Germany Ulrike Cress Knowledge Media Research Center, Tuebingen, Germany Author Note Johannes Moskaliuk, Department of Applied Cognitive Psychology and Media Psychology, University of Tuebingen, Tuebingen, Germany; Joachim Kimmerle, Department of Applied Cognitive Psychology and Media Psychology, University of Tuebingen, Tuebingen, Germany; Ulrike Cress, Knowledge Construction Lab, Knowledge Media Research Center, Tuebingen, Germany. Correspondence concerning this article should be addressed to Joachim Kimmerle, Department of Applied Cognitive Psychology and Media Psychology, University of Tuebingen, Konrad-Adenauer-Str. 40, D-72072 Tuebingen, Germany. E-mail: j.kimmerle@iwm-kmrc.de Title Page -- anything identifying the author should be on this page.