An Evaluation of Techniques for Reducing Spatial Interference in Single Display Groupware

When several users interact with Single Display Groupware (SDG) (Stewart et al., 1999) applications over a shared display, the potential exists for one user’s actions to spatially interfere with another’s (Tse et al., 2004; Zanella and Greenberg, 2001). We empirically evaluate four techniques for mitigating spatial interference in SDG: shared display with object ownership, spatially split display, shared display with uniform transparency between users’ data, and shared display with gradient transparency from one edge of the display to the other. Apart from time and error performance measures, we also consider the impact of each technique on user’s voluntary partitioning of the available display space. Results show that the best approach in terms of performance is to share the entire display with appropriate use of transparency techniques for minimizing interference, and allow users to decide for themselves how they wish to partition the space, rather than pre-partitioning it for them. Results also show that complete sharing may result in misuse of screen space and demonstrate the potential of gradient transparency as a technique that effectively balances costs and benefits of both sharing and partitioning.