Reward-Balancing for Statistical Spoken Dialogue Systems using Multi-objective Reinforcement Learning

Stefan Ultes, Pawel Budzianowski, Iñigo Casanueva, Nikola Mrksic, Lina Maria Rojas-Barahona, Pei-Hao Su, Tsung-Hsien Wen, Milica Gasic, Steve J. Young

Abstract: Reinforcement learning is widely used for dialogue policy optimization where the reward function often consists of more than one component, e.g., the dialogue success and the dialogue length. In this work, we propose a structured method for finding a good balance between these components by searching for the optimal reward component weighting. To render this search feasible, we use multi-objective reinforcement learning to significantly reduce the number of training dialogues required. We apply our proposed method to find optimized component weights for six domains and compare them to a default baseline.