Iterative Dual-Model Alignment for Story Evaluation

Bruce Qin, Dan Goldwasser


Abstract
Large language models (LLMs) can both evaluate and explain text quality; however, most existing evaluators operate as static classifiers and lack the ability to refine their reasoning through interaction. We propose an Iterative Alpha–Beta Learning framework that jointly trains two complementary 8B models: an Alpha (𝛼) classifier that assesses pairwise story engagement, and a Beta (𝛽) generator that produces structured, rubric-guided comparative explanations. The two models co-evolve within a closed feedback loop: 𝛼 provides probabilistic preference signals to guide 𝛽’s Direct Preference Optimization (DPO), while 𝛽’s improved explanations are reintegrated to retrain 𝛼 via a KL-based contrastive objective. This dual optimization enables mutual learning: 𝛼 gains interpretability and robustness from 𝛽’s textual rationales, while 𝛽 acquires stronger alignment and discriminative precision from 𝛼’s confidence deltas. Experiments on human-annotated story-pair datasets HANNA show that the proposed system consistently outperforms strong single-model baselines in both accuracy and explanation quality across multiple iterative rounds.
Anthology ID:
2026.acl-long.648
Volume:
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
July
Year:
2026
Address:
San Diego, California, United States
Editors:
Maria Liakata, Viviane P. Moreira, Jiajun Zhang, David Jurgens
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
14251–14264
Language:
URL:
https://preview.aclanthology.org/ingest-acl/2026.acl-long.648/
DOI:
Bibkey:
Cite (ACL):
Bruce Qin and Dan Goldwasser. 2026. Iterative Dual-Model Alignment for Story Evaluation. In Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 14251–14264, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Iterative Dual-Model Alignment for Story Evaluation (Qin & Goldwasser, ACL 2026)
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https://preview.aclanthology.org/ingest-acl/2026.acl-long.648.pdf
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