Semi-Supervised Learning to Improve Detection of Factual and Causal Errors in Language Models’ Explanations

Mingxuan Liu, Han Yuan, Yilin Wu, Li Zhang, Zheng Ma


Abstract
Language models (LMs) are increasingly used to generate decisions and explanations for high-stakes financial tasks, but these explanations can contain factual inconsistencies with the underlying claim or invalid causal reasoning. We propose a two-step auditing framework that decomposes each explanation into reasoning points and verifies them using natural language inference (NLI): (i) claim ⇒ point for factuality verification and (ii) point ⇒ conclusion for causality verification. To reduce reliance on expensive expert annotations, we study effective fine-tuning strategies based on semi-supervised learning (SSL) for NLI verifiers, leveraging abundant unlabeled explanations via pseudo-labeling and FreeMatch with self-adaptive confidence thresholds. Experiments across small language models and both encoder-only and decoder-only verifiers under varying labeling budgets show that SSL consistently outperforms the pre-trained baseline and supervised fine-tuning. FreeMatch is generally more robust than simple pseudo-labeling, suggesting better utilization of unlabeled data for scaling error detection of LMs’ generations.
Anthology ID:
2026.groundlm-1.11
Volume:
Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Yimu Wang, Yee Man Choi, Di Wu, Siqi Ouyang, Mozhgan Nasr Azadani, Yi R. (May) Fung
Venues:
GroundLM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
141–147
Language:
URL:
https://aclanthology.org/2026.groundlm-1.11/
DOI:
Bibkey:
Cite (ACL):
Mingxuan Liu, Han Yuan, Yilin Wu, Li Zhang, and Zheng Ma. 2026. Semi-Supervised Learning to Improve Detection of Factual and Causal Errors in Language Models’ Explanations. In Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026), pages 141–147, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Semi-Supervised Learning to Improve Detection of Factual and Causal Errors in Language Models’ Explanations (Liu et al., GroundLM 2026)
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PDF:
https://aclanthology.org/2026.groundlm-1.11.pdf