Engagement Theory: A framework for technology-based teaching and learning
The fundamental idea underlying engagement theory is that students must be meaningfully engaged in learning activities through interaction with others and worthwhile tasks.
Network analysis in online discussions in two classes shows, not surprisingly, that asking probing questions and challenging posts results in more learner engagement than simple "cheerleading" posts like "Great job!"
New link: http://www.eschoolnews.com/2008/05/08/online-insight-challenges-beat-cheerleading/