We present a tablet-based system to collaboratively track discussion topics and ideas in a seminar-style discussion classroom. Each student uses his or her own tablet to share text ideas in a synchronized, visual environment. The system is designed to promote diverse participation and increase engagement. Our findings are based on observations of twelve class sessions and interviews with participating students. Instead of simply introducing an additional text-based communication channel into the classroom, we find that the system creates a new "stage" (in the Goffman sense) on which students could perform in ways that the main spoken stage could not support. This stage coexists with spoken communication, and augments how students attend to the material and each other. We conclude that spoken participation alone poses barriers for some participants and the addition of a non-oral, text-based stage can help establish equitable and engaging discussions in the class.

In this paper, we describe backchan.nl, a web based backchannel system that focuses on providing greater audience participation during question and answer sessions. The system allows audience members to use a web-based service to propose questions and comments, and to vote on the questions of others. Top rated submissions are projected into the presentation space where audience members, moderators, and panelists can see them. We discuss the results of deploying this system at many different kinds of conferences and relate those results to the particular design of our system, demonstrating how backchannel systems can be more than just shared chat rooms. From our experience with this work, we discuss the broader implications of configurable mediated social spaces and how subtle design decisions can influence user experience