We offer a new approach to emergent knowledge in processes of conceptual change in dyadic interaction by drawing on Pickering's ("The Mangle of Practice," The University of Chicago Press, London, 1995) Mangle of Practice theory, which theorizes the emergence of new scientific knowledge as occurring due to material resistance and human accommodations to such resistance. We use Commognition (Sfard in "Thinking as communicating," Cambridge University Press, New York, 2008), which conceptualizes learning as a change in discourse, and conceptual change as change in meta-discursive rules, to examine the interaction between several dyads working on proportional reasoning tasks. These dyads were selected for close scrutiny based on a large previous experimental study designed to examine the most productive constellation for pairing students of different levels with or without a hypothesis testing device. The Mangle helps us theorize the emergent, unpredictable aspects of learning and conceptual change. We provide three criteria for examining the productivity of the interaction: Availability of an alternative discourse (proportional vs. additive), Resistance of material/disciplinary agency and Positioning of students to make meta-discursive shifts. We discuss this model as an aid for monitoring and designing learning situations that enhance conceptual change.