Justice in Judgment: Unveiling (Hidden) Bias in LLM-assisted Peer Reviews

Sai Suresh Macharla Vasu, Ivaxi Sheth, Hui-Po Wang, Ruta Binkyte, Mario Fritz


Abstract
The adoption of large language models (LLMs) is transforming the peer review process, from assisting reviewers in writing detailed evaluations to generating entire reviews automatically. While these capabilities offer new opportunities, they also raise concerns about fairness and reliability. In this paper, we investigate bias in LLM-generated peer reviews through controlled interventions on author metadata, including affiliation, gender, seniority, and publication history. Our analysis consistently shows a strong affiliation bias favoring authors from highly ranked institutions. We also identify directional preferences associated with seniority and prior publication record, which can influence acceptance decisions for borderline papers. Gender effects are smaller but present in several models. Notably, implicit biases become more pronounced when examining token-level soft ratings, suggesting that alignment may mask but not fully eliminate underlying preferences.
Anthology ID:
2026.findings-acl.14
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
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
307–330
Language:
URL:
https://preview.aclanthology.org/ingest-acl/2026.findings-acl.14/
DOI:
Bibkey:
Cite (ACL):
Sai Suresh Macharla Vasu, Ivaxi Sheth, Hui-Po Wang, Ruta Binkyte, and Mario Fritz. 2026. Justice in Judgment: Unveiling (Hidden) Bias in LLM-assisted Peer Reviews. In Findings of the Association for Computational Linguistics: ACL 2026, pages 307–330, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Justice in Judgment: Unveiling (Hidden) Bias in LLM-assisted Peer Reviews (Vasu et al., Findings 2026)
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PDF:
https://preview.aclanthology.org/ingest-acl/2026.findings-acl.14.pdf
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