Evaluating LLM-generated Explanatory Dialogue Turns through Dialogue Completion

Yi-Sheng Hsu, Nils Feldhus, Manfred Stede


Abstract
Synthetic explanatory dialogues hold promise for applications from tutoring systems to model rationalization, yet their quality is often deemed inferior to human-authored conversations. This study uses dialogue completion as a lens to investigate the nuanced differences between human-spoken, human-written, and synthetic explanatory dialogue. By evaluating LLM-generated turns against original turns using the FED and IXQuisite test suites, we uncover a significant bias in the FED metric towards written language, which may penalize the interactivity of spoken dialogue. We find that three popular LLMs (Mistral, Llama, Claude) replicate this pattern, excelling in fluency, but struggling with conversational engagement, particularly on spoken dialogue transcripts. More importantly, we demonstrate that these models can significantly improve their performance through a zero-shot, iterative self-refinement method. By providing feedback based on their specific weaknesses, we show that LLMs can iteratively adapt their outputs to better resemble the interactive qualities of human dialogue.
Anthology ID:
2026.emnlp-main.72
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
1649–1679
Language:
URL:
https://aclanthology.org/2026.emnlp-main.72/
DOI:
Bibkey:
Cite (ACL):
Yi-Sheng Hsu, Nils Feldhus, and Manfred Stede. 2026. Evaluating LLM-generated Explanatory Dialogue Turns through Dialogue Completion. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 1649–1679, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Evaluating LLM-generated Explanatory Dialogue Turns through Dialogue Completion (Hsu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.72.pdf