Listening to the Echo: User-Reaction Aware Policy Optimization via Scalar-Verbal Hybrid Reinforcement Learning

Jing Ye, Xinpei Zhao, Lu Xiang, Yaping Zhang, Chengqing Zong


Abstract
While current emotional support dialogue systems typically rely on expert-defined scalar rewards for alignment, these signals suffer from severe information sparsity. They cannot explain why a response failed or how to adapt to dynamic user states, often failing to capture interaction-level conversational consequences reflected in subsequent user responses. We explore whether user reactions can serve as an additional behavior-level optimization signal for emotional support alignment. Therefore, we propose Reaction Aware Policy Optimization (RAPO), a framework that optimizes over interaction consequences rather than rubric scores. RAPO treats dialogue as a reaction-driven process and utilizes simulated user responses to generate dense natural-language feedback through three core components: (1) Hindsight Dialogue Selection, which isolates pivotal turns that meaningfully alter user emotional trajectories; (2) Generative Hindsight Feedback, which transforms user reactions into contrastive ranking signals and natural-language critiques; and (3) Scalar–Verbal Hybrid Policy Optimization, which couples scalar reward optimization for global alignment with verbal feedback distillation for fine-grained semantic refinement. Extensive experiments on ESC and Sotopia demonstrate that RAPO significantly outperforms strong RL baselines in driving positive interaction outcomes.
Anthology ID:
2026.findings-emnlp.73
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
1485–1515
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.73/
DOI:
Bibkey:
Cite (ACL):
Jing Ye, Xinpei Zhao, Lu Xiang, Yaping Zhang, and Chengqing Zong. 2026. Listening to the Echo: User-Reaction Aware Policy Optimization via Scalar-Verbal Hybrid Reinforcement Learning. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 1485–1515, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Listening to the Echo: User-Reaction Aware Policy Optimization via Scalar-Verbal Hybrid Reinforcement Learning (Ye et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.73.pdf