Interaction in task-oriented human-human dialogue: the effects of different turn-taking policies

In human-human dialogue, the allocation of turns between the participants is normally managed smoothly, without the participants paying much attention to it. In contrast, for spoken dialogue systems turn allocation is a difficult task, and often technical restrictions are introduced to simplify it. In this paper we investigate, by comparing two experimentally collected corpora of human-human task oriented dialogue, what the consequences are of imposing one particular kind of restriction, namely that of using a simplex channel managed by push-to-talk (PTT). We found, as expected, a loss of interactivity in the PTT condition (fewer, longer turns; more silences), but surprisingly, no loss of efficiency; in fact, the subjects in the PTT condition were able to finish their task in roughly the same time, while using fewer words along the way. We analyse here the differences in the interaction patterns and the interplay of ´naturalness´ and efficiency as relevant factors for practical system development.