In the participationist perspective, learning is viewed in terms of how students transform their participation. However, many of the seminal papers discussing the participationist framework are vague on specific details about what student participation really looks like on a more fine-grained scale. As part of a larger project to understand the role of student participation in learning, we are trying to characterize the ways in which physics students participate in group activities and discussions while they are constructing new knowledge. The context for our study is a student-centered introductory calculus-based physics class structured around the Investigative Science Learning Environment (ISLE) philosophy. In this paper we will discuss some of the patterns of participation we have found and some of the challenges we have encountered in trying to code and quantify student participation from analyzing video data.