Importance-Driven Turn-Bidding for Spoken Dialogue Systems

Proceedings of the 48th Annual Meeting of the Association for Computational Linguistics, pages 177–185, Uppsala, Sweden, 11-16 July 2010. c⃝2010 Association for Computational Linguistics Importance-Driven Turn-Bidding for Spoken Dialogue Systems Ethan O. Selfridge and Peter A. Heeman Center for Spoken Language Understanding Oregon Health & Science University 20000 NW Walker Rd., Beaverton, OR, 97006 selfridg@ohsu.edu, heemanp@ohsu.edu Abstract Current turn-taking approaches for spoken dialogue systems rely on the speaker re- leasing the turn before the other can take it. This reliance results in restricted interac- tions that can lead to inefficient dialogues. In this paper we present a model we re- fer to as Importance-Driven Turn-Bidding that treats turn-taking as a negotiative pro- cess. Each conversant bids for the turn based on the importance of the intended utterance, and Reinforcement Learning is used to indirectly learn this parameter. We find that Importance-Driven Turn-Bidding performs better than two current turn- taking approaches in an artificial collabo- rative slot-filling domain. The negotiative nature of this model creates efficient dia- logues, and supports the improvement of mixed-initiative interaction. 1 Introduction As spoken dialogue systems are designed to perform ever more elaborate tasks, the need for mixed-initiative interaction necessarily grows. Mixed-initiative interaction, where agents (both artificial and human) may freely contribute to reach a solution efficiently, has long been a focus of dialogue systems research (Allen et al., 1999; Guinn, 1996). Simple slot-filling tasks might not require the flexible environment that mixed- initiative interaction brings but those of greater complexity, such as collaborative task comple- tion or long-term planning, certainly do (Fergu- son et al., 1996). However, translating this interac- tion into working systems has proved problematic (Walker et al., 1997), in part to issues surround- ing turn-taking: the transition from one speaker to another. Many computational turn-taking approaches seek to minimize silence and utterance overlap during transitions. This leads to the speaker con- trolling the turn transition. For example, systems using the Keep-Or-Release approach will not at- tempt to take the turn unless it is sure the user has released it. One problem with this approach is that the system might have important informa- tion to give but will be unable to get the turn. The speaker-centric nature of current approaches does not enable mixed-initiative interaction and results in inefficient dialogues. Primarily, these approaches have been motivated by smooth tran- sitions reported in the human turn-taking studies of Sacks et al. (1974) among others. Sacks et al. also acknowledge the negotiative nature of turn-taking, stating that the “the turn as unit is interactively determined”(p. 727). Other studies have supported this, suggesting that hu- mans negotiate the turn assignment through the use of cues and that these cues are motivated by the importance of what the conversant wishes to contribute (Duncan and Niederehe, 1974; Yang and Heeman, 2010; Schegloff, 2000). Given this, any dialogue system hoping to interact with humans efficiently and naturally should have a negotiative and importance-driven quality to its turn-taking protocol. We believe that, by focus- ing on the rationale of human …

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