用动态标准提升大模型奖励模型的可靠性,防止表面优化。
CARMO: Dynamic Criteria Generation for Context-Aware Reward Modelling
- 先生成与上下文相关的评价标准,再打分
- 零样本下比现有方法高2.1%得分
- 适合需要高质量对齐的模型训练场景
大型语言模型的奖励建模易受奖励劫持影响,导致模型偏好生成列表或冗长回答等表面特征。在人类反馈强化学习(RLHF)等后训练阶段,错误的奖励信号常引发模型优化虚假相关性而非真实质量。本文提出上下文感知奖励建模(CARMO),通过大语言模型动态生成逻辑一致性、清晰度、深度等与任务相关的评价标准,再据此评分。理论分析表明该机制可缓解奖励劫持。实验显示,CARMO可被压缩为小型模型,降低对齐计算成本。在零样本设置下,于Reward Bench上实现2.1%的性能提升;在Mistral-Base(7B)上,基于CARMO标注的数据集对齐后,获得LC-WR 22.5%和WR 21.1%的指标。
原文摘要 · Abstract (English)
Reward modeling in large language models is susceptible to reward hacking, causing models to latch onto superficial features such as the tendency to generate lists or unnecessarily long responses. In reinforcement learning from human feedback (RLHF) and more generally during post-training flawed reward signals often lead to outputs that optimize for these spurious correlates instead of genuine quality or correctness. We propose Context-Aware Reward Modeling (CARMO), a novel approach that first generates dynamic, context-relevant criteria to ground the reward model before producing reward scores. Unlike prior methods that rely on static rubrics, CARMO leverages large language models (LLMs) to adaptively create evaluation criteria such as logical consistency, clarity, and depth tailored to the user query. Our theoretical analysis shows that such criteria generation can mitigate reward hacking. We further demonstrate that CARMO can be distilled into smaller models, reducing the computational cost of alignment. We establish a new state-of-the-art performance in zero-shot settings for generative models, achieving a 2.1\% improvement on Reward Bench. Furthermore, alignment performed on the CARMO-curated preference dataset achieves 22.5\% and 21.1\% LC-WR and WR, respectively, on Mistral-Base (7B).
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