Future mixed reality systems will need to support large numbers of simultaneous, nonexpert users at reasonable per-user costs if the systems are to be widely deployed within society in the short to medium term. We have constructed a prototype of such a system, an interactive entertainment space called Ada that was designed to behave like a simple organism. Using Ada we conducted two studies: the first assessing the effect of varying the operating parameters of the space on the collective behavior and attitudes of its users, and the second assessing the relationships among user demographics, behavior, and attitudes. Our results showed that small changes in the ambient settings of the environment have a significant effect on both user attitudes and behavior, and that the changes in user attitudes do not necessarily correspond to the environmental changes. We also found that individual user opinions are affected by demographics and reflected in overt behavior. Using these results, we propose some tentative guidelines for the design of future shared mixed reality spaces.