Abstract: This paper presents empirical results of the use of a novel decision support prototype for emergency response situations, which was designed to enhance the understanding of the relative desirability of one potential course of action versus another. We have termed this understanding “option awareness.” In particular, this paper describes the process employed by pairs of experiment participants while performing emergency responder roles using different types of “decision space” visualizations to help them collaborate on decisions. We examined the decision making process via a detailed analysis of the communication between the cooperating team members. The results yield implications for design approaches for visualizing option awareness. © 2012 ISCRAM.