From Preferences to Scores: Semi-Supervised Multi-Trait Essay Scoring with LLM Pairwise Preferences and Few Human Anchors

Takumi Shibata, Yuichi Miyamura


Abstract
Multi-trait automated essay scoring (AES) provides trait-level scores as feedback but requires costly annotations across multiple traits to train accurate scoring models. To alleviate this annotation burden, we propose MTPAS (Multi-Trait Preference-to-Absolute Scoring), a semi-supervised framework that learns relative score orderings from LLM-generated pairwise preferences and calibrates them to absolute rubric scales using a small set of human-scored anchor essays in an end-to-end manner. To this end, MTPAS jointly optimizes three objectives: a Bradley–Terry pairwise preference loss, a regression loss on the anchor essays, and a Sinkhorn divergence-based distribution regularizer. The model adopts a bifactor architecture that decomposes essay representations into a shared general factor and trait-specific residuals, improving robustness against noisy LLM-generated preferences. We further introduce pairwise rubric compression, which reformulates the original score-level rubrics into concise comparative criteria, reducing the inference cost of collecting LLM preferences. On ASAP and ASAP++, MTPAS achieves 91.4% of the fully supervised SoTA performance with only 30 anchor essays per prompt and further narrows the gap with 200 anchors. Under the same anchor budget, MTPAS outperforms conventional multi-trait AES baselines at every anchor size investigated in this study.
Anthology ID:
2026.aacl-long.273
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
6041–6057
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URL:
https://aclanthology.org/2026.aacl-long.273/
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Cite (ACL):
Takumi Shibata and Yuichi Miyamura. 2026. From Preferences to Scores: Semi-Supervised Multi-Trait Essay Scoring with LLM Pairwise Preferences and Few Human Anchors. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 6041–6057, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
From Preferences to Scores: Semi-Supervised Multi-Trait Essay Scoring with LLM Pairwise Preferences and Few Human Anchors (Shibata & Miyamura, AACL-IJCNLP 2026)
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https://aclanthology.org/2026.aacl-long.273.pdf