Revision with unchanged content. The open content movement is enabling the advent of a major turn in information-based products through the enormous potential of collective intelligence. The Linux operating system, the Firefox internet browser, the online encyclopedia Wikipedia, the Public Library of Science, or the MIT’s OpenCourseWare project, are all striking successes. What are the factors that contribute to such high-quality products in open content practices? This study uses a group perspective to examine the group factors that lead to high-quality products in open content communities. A theoretical model is developed, based on the Input-Process-Output approach of group research in social psychology and on the Time, Interaction, and Performance Theory proposed by McGrath (1991). A quantitative study of the detailed activity logs of Wikipedia was designed and tested. The analysis should help to answer the questions: - Can a group perspective provide valuable insights in explaining the success of open content projects? What makes open content practices so different from other types of practices? The book is addressed to professionals whose field is related to information-based products, open content and open source communities. It is also directed towards researchers in Business Administration and Social Psychology.--Ce texte fait référence à l'édition Broché .