What can I say?

This paper presents experimental results comparing two different designs for a spoken language interface to entail. We compare a mixed-initiative dialogue style, in which users can flexibly control the dialogue, to a systemiuitiative dialogue style, in which the system controls the dialogue. Our results show that even though the mixedinitiative system is more eflicient, as measured by number of turns, or elapsed time to complete a set of email tasks, users prefer the system-initiative interface. We posit that these preferences arise from the fact that the system initiative inter&e is easier to learn and more predictable.