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Main Authors: Li, Dawei, Sun, Renliang, Huang, Yue, Zhong, Ming, Jiang, Bohan, Han, Jiawei, Zhang, Xiangliang, Wang, Wei, Liu, Huan
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2502.01534
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author Li, Dawei
Sun, Renliang
Huang, Yue
Zhong, Ming
Jiang, Bohan
Han, Jiawei
Zhang, Xiangliang
Wang, Wei
Liu, Huan
author_facet Li, Dawei
Sun, Renliang
Huang, Yue
Zhong, Ming
Jiang, Bohan
Han, Jiawei
Zhang, Xiangliang
Wang, Wei
Liu, Huan
contents Large Language Models (LLMs) as judges and LLM-based data synthesis have emerged as two fundamental LLM-driven data annotation methods in model development. While their combination significantly enhances the efficiency of model training and evaluation, little attention has been given to the potential contamination brought by this new model development paradigm. In this work, we expose preference leakage, a contamination problem in LLM-as-a-judge caused by the relatedness between the synthetic data generators and LLM-based evaluators. To study this issue, we first define three common relatednesses between the data generator LLM and the judge LLM: being the same model, having an inheritance relationship, and belonging to the same model family. Through extensive experiments, we empirically confirm the bias of judges towards their related student models caused by preference leakage across multiple LLM baselines and benchmarks. Further analysis suggests that preference leakage is a pervasive and real-world problem that is harder to detect compared to previously identified biases in LLM-as-a-judge scenarios. All of these findings imply that preference leakage is a widespread and challenging problem in the area of LLM-as-a-judge. We release all codes and data at: https://github.com/David-Li0406/Preference-Leakage.
format Preprint
id arxiv_https___arxiv_org_abs_2502_01534
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Preference Leakage: A Contamination Problem in LLM-as-a-judge
Li, Dawei
Sun, Renliang
Huang, Yue
Zhong, Ming
Jiang, Bohan
Han, Jiawei
Zhang, Xiangliang
Wang, Wei
Liu, Huan
Machine Learning
Artificial Intelligence
Computation and Language
Large Language Models (LLMs) as judges and LLM-based data synthesis have emerged as two fundamental LLM-driven data annotation methods in model development. While their combination significantly enhances the efficiency of model training and evaluation, little attention has been given to the potential contamination brought by this new model development paradigm. In this work, we expose preference leakage, a contamination problem in LLM-as-a-judge caused by the relatedness between the synthetic data generators and LLM-based evaluators. To study this issue, we first define three common relatednesses between the data generator LLM and the judge LLM: being the same model, having an inheritance relationship, and belonging to the same model family. Through extensive experiments, we empirically confirm the bias of judges towards their related student models caused by preference leakage across multiple LLM baselines and benchmarks. Further analysis suggests that preference leakage is a pervasive and real-world problem that is harder to detect compared to previously identified biases in LLM-as-a-judge scenarios. All of these findings imply that preference leakage is a widespread and challenging problem in the area of LLM-as-a-judge. We release all codes and data at: https://github.com/David-Li0406/Preference-Leakage.
title Preference Leakage: A Contamination Problem in LLM-as-a-judge
topic Machine Learning
Artificial Intelligence
Computation and Language
url https://arxiv.org/abs/2502.01534