The present study focuses on the observation of learning processes as they emerge in the context of conversations among two students in three successive tasks designed to foster conceptual change in proportional reasoning. The three tasks were set according to a pre-test treatment post-test paradigm. In the pre-test and the post-test tasks, the two students solved individually several items in the presence of an experimenter. In the treatment task, the two students worked as a dyad to solve similar items; they used a balance to check their conclusions and subsequently continued solving the items when the weighing did not match their expectations. A micro-genetic approach was adopted to develop new analytical tools to observe what happened in the conversation (both socially and cognitively). Throughout the three successive tasks, the interplay between tools, peers, experimenter, and task demands and how they are managed through the rules of conversation, were observed. The paper identified four processes that involved the emergence of new high-order strategies from coordinated actions distributed among peers, the guidance of the experimenter in coordinating actions, and ways the participation in solving a previous task was actualized in a successive one.