Effects of Timing on Users' Agency during Mixed-Initiative Interaction.

We explore the role of timing in situations where a human user and semi-autonomous software can each initiate actions, building on cognitive theories of rhythmic expectation and mutual temporal adaptation during conversation. Two controlled experiments demonstrate that adjustments to the rhythm of back-and- forth interaction have significant effects on perceived agency, task performance and stress. Conclusions include design guidance that establishing a predictable rhythm of interaction is likely to be beneficial for mixed initiative systems.