Spatially-aware or spatially-agnostic? Elicitation and evaluation of user-defined cross-device interactions

Cross-device interaction between multiple mobile devices is a popular field of research in HCI. However, the appropriate design of this interaction is still an open question, with competing approaches such as spatiallyaware vs. spatially-agnostic techniques. In this paper, we present the results of a two-phase user study that explores this design space: In phase 1, we elicited gestures for typical mobile cross-device tasks from 4 focus groups (N=17). The results show that 71% of the elicited gestures were spatially-aware and that participants strongly associated cross-device tasks with interacting and thinking in space. In phase 2, we implemented one spatially-agnostic and two spatially-aware techniques from phase 1 and compared them in a controlled experiment (N=12). The results indicate that spatially-aware techniques are preferred by users and can decrease mental demand, effort, and frustration, but only when they are designed with great care. We conclude with a summary of findings to inform the design of future cross-device interactions.