Justice or Prejudice? Quantifying Biases in LLM-as-a-Judge
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "arXiv — non-exclusive license to distribute" does not allow redistributing the text itself. Original — arxiv.org/pdf/2410.02736
Summary
LLMs are now routinely used to grade other models' outputs, both in benchmarks and as reward signals during training. Their impartiality, however, has been studied only piecemeal, and often with costly, subjective human annotation. Ye et al. propose CALM (Comprehensive Assessment of Language Model Judge Biases), a framework that measures judge bias without human raters.
CALM defines a taxonomy of 12 bias types and probes each one with an attack-and-detect procedure. A second LLM (GPT-4o) makes principle-guided edits to a candidate answer or to the system instruction. Examples include padding a response, inserting a fabricated book citation, or telling the judge that an answer was refined. The judge's verdicts on the original and perturbed inputs are then compared. Tests cover fact-related reasoning, answer refinement and alignment data, in both pairwise-comparison and scoring setups.
Across six popular judge LLMs, the strongest models are fairly robust overall, but notable biases remain for particular bias types and tasks. The work offers a scalable, reproducible auditing tool and warns practitioners against trusting automatic verdicts uncritically.
Key points
- Bias types covered (12): position, verbosity, compassion-fade (model names vs. anonymous aliases), bandwagon, distraction, fallacy-oversight, authority, sentiment, diversity (identity mentions), CoT, self-preference and refinement-aware bias.
- Datasets by evaluation aspect:
- Fact-related: GSM8K, MATH, ScienceQA.
- Refinement-aware: CommonsenseQA, TruthfulQA.
- Alignment: OpenOrca, emerton_dpo.
- Answer generation: candidate answers come from Llama3-8B, Llama3-70B, Mistral-7B and Mixtral-8x22B. GPT-4o injects the biased modifications.
- Judges evaluated: six LLMs, including ChatGPT, GPT-4o, GLM-4, Claude-3.5-Sonnet and Qwen-72b.
- Metrics: Robustness Rate (RR), Consistency Rate (CR), Original vs. Hacked Accuracy, and Error Rate. A judge counts as unbiased when its score or preference does not change after the perturbation.
Cited by
- LongBench v2: Towards Deeper Understanding and Reasoning on Realistic Long-context Multitasks
- LLMs-as-Judges: A Comprehensive Survey on LLM-based Evaluation Methods
Cite
@misc{ye2024justice,
title = {{Justice or Prejudice? Quantifying Biases in LLM-as-a-Judge}},
author = {Ye, Jiayi and Wang, Yanbo and Huang, Yue and Chen, Dongping and Zhang, Qihui and Moniz, Nuno and Gao, Tian and Geyer, Werner and Huang, Chao and Chen, Pin-Yu and Chawla, Nitesh V and Zhang, Xiangliang},
year = {2024},
doi = {10.48550/arxiv.2410.02736},
eprint = {2410.02736},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.2410.02736}
}References
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