Collective Usability: Using Simulation Tools To Explore Embodied Design Challenges In Immersive, Shared Mixed-Reality Experiences

In this paper we define the concept of collective usability, a complex systems perspective on usability that positions an entire group, not an individual, as the unit of analysis. Shared XR experiences have inherent temporal and spatial properties that produce emergent, collective impacts which can impede learners' engagement. Assembling large groups of users to test multiple design configurations is both logistically and financially impractical, however. We demonstrate the practical value of exploring the design space of an XR experience with a simple observation-informed Agent-Based Model. We used the model to explore how changes in the number of simultaneous users, and in the size, placement, and interaction duration of the proffered interactives, could affect collective access to a large-scale, mixed-reality, multi-user museum exhibit. (Collective access, an element of collective usability, is the degree to which users can gain access to each of the different interactives.) With this simple model, we explored (1) how the bottom-up propagation of individual-level design properties can affect collective outcomes, as when certain interactives' linger times cause a bottleneck, and (2) how the top-down propagation of collective design constraints can be used to guide individual-level design, as when we determined thresholds for the "stickiness" and "repeat allure" of an interactive to improve collective access. The final design of the exhibit implemented many of the design guidelines uncovered by the model. We argue that collective usability models could be useful for addressing a range of collective usability issues, beyond collective access, for temporally and spatially sensitive XR learning environments.