This dissertation consists of two articles which discuss the establishment of collective cognitive responsibility in high school mathematics classrooms. I use collective cognitive responsibility as a framework for interpreting the extent to which students see themselves as responsible for building knowledge as a community. I adapted this framework to apply to secondary mathematics classrooms; in this context, I determined that collective cognitive responsibility includes a responsibility for justifying mathematical ideas as a group through discourse, but also for offering ideas and listening to the ideas of others regardless of whether those ideas are known to be correct. The first article is an empirical study that explores the different ways that eight students, members of a mathematics class which often incorporated collaborative learning structures, expressed (or did not express) collective cognitive responsibility. This study included viewing session interviews in which students watched video clips of their own participation in collaborative work and described their responsibilities as members of a group or the class as a whole. In the second article, I situate collective cognitive responsibility in the literature on collaborative learning in mathematics classrooms and describe how investigating student perspectives, particularly through viewing session interviews, can provide additional insights about the quality of collaboration. I explain how the approach helps to fill in a gap left by other methodologies. I use data from the empirical study to illustrate the affordances of the interview data.