Large Language Models Are Still Misled by Simple Bias Ensembles

Zhouhao Sun, Zhiyuan Kan, Xiao Ding, Li Du, Bibo Cai, Yang Zhao, Bing Qin, Ting Liu


Abstract
With the evolution of large language models (LLMs), their robustness against individual simple biases has been enhanced. However, we observe that the ensemble of multiple simple biases still exerts a significant adverse impact on LLMs. Given that real-world data samples are typically confounded by a wide range of biases, LLMs tend to exhibit unstable performance when deployed in high-stakes real-world scenarios such as clinical diagnosis and legal document analysis. However, previous benchmarks are constrained to datasets where each sample is manually injected with only one type of bias. To bridge this gap, we propose a multi-bias benchmark where each sample contains multiple types of biases. Experimental results reveal that existing LLMs and debiasing methods perform poorly on this benchmark, highlighting the challenge of eliminating such compounded biases.
Anthology ID:
2026.findings-acl.971
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:
19444–19455
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URL:
https://preview.aclanthology.org/ingest-acl/2026.findings-acl.971/
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Bibkey:
Cite (ACL):
Zhouhao Sun, Zhiyuan Kan, Xiao Ding, Li Du, Bibo Cai, Yang Zhao, Bing Qin, and Ting Liu. 2026. Large Language Models Are Still Misled by Simple Bias Ensembles. In Findings of the Association for Computational Linguistics: ACL 2026, pages 19444–19455, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Large Language Models Are Still Misled by Simple Bias Ensembles (Sun et al., Findings 2026)
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https://preview.aclanthology.org/ingest-acl/2026.findings-acl.971.pdf
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