Fin-Bias: Comprehensive Evaluation for LLM Decision-Making under human bias in Finance Domain

Xiaoyu Hu, Jinman Zhao


Abstract
Large language models (LLMs) are increasingly deployed in financial contexts, raising critical concerns about reliability, alignment, and susceptibility to adversarial manipulation. While prior finance-related benchmarks assess LLMs’ capabilities in stock trading, they are often restricted to small sample and fail to demonstrate LLM susceptibility to context with potential human bias. We introduce Fin-Herding (financial herding under long and uncertain financial context), a benchmark for evaluating LLM investment decision-making when faced with uncertainty and possible human-biased opinions. Fin-Herding includes 8868 long firm-specific analyst reports, including firm aspects summarized and analyzed by sophisticated analysts with investment ratings (Bullish/Neutral/Bearish) spanning from various industries. We present large language models with firm analyst reports with/without analyst investment ratings and even with ’fake’ rating, to get investment ratings generated by LLMs. Our results reveal that LLMs tend to herd the explicit bias in context. We also develop a method to detect potential human opinions, which can encourage LLMs to think independently, some models even exceed human performance in predicting future stock return.
Anthology ID:
2026.findings-acl.279
Volume:
Findings of the Association for Computational Linguistics: ACL 2026
Month:
July
Year:
2026
Address:
San Diego, California, United States
Editors:
Maria Liakata, Viviane P. Moreira, Jiajun Zhang, David Jurgens
Venue:
Findings
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Publisher:
Association for Computational Linguistics
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Pages:
5678–5694
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URL:
https://preview.aclanthology.org/ingest-acl/2026.findings-acl.279/
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Cite (ACL):
Xiaoyu Hu and Jinman Zhao. 2026. Fin-Bias: Comprehensive Evaluation for LLM Decision-Making under human bias in Finance Domain. In Findings of the Association for Computational Linguistics: ACL 2026, pages 5678–5694, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Fin-Bias: Comprehensive Evaluation for LLM Decision-Making under human bias in Finance Domain (Hu & Zhao, Findings 2026)
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https://preview.aclanthology.org/ingest-acl/2026.findings-acl.279.pdf
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