In this paper, we consider the effect of co-adaptive learning on the training and evaluation of real-time, interactive machine learning systems, referring to specific examples in our work on action-perception loops, feedback for virtual tasks, and training of regression and temporal models. Through these studies we have encountered challenges when designing and assessing expressive, multimodal
... [Show full abstract] interactive systems. We discuss those challenges to machine learning and human-computer interaction, proposing future directions and research.