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RRM: Robust Reward Model Training Mitigates Reward Hacking

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arxiv 2409.13156 v2 pith:2NZEOYYH submitted 2024-09-20 cs.CL

classification cs.CL
keywords rewardartifactspreferencesmodeltrainingmodelspoliciesresponse
verification ladder T0 review T1 audit T2 compute T3 formal
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Reward models (RMs) play a pivotal role in aligning large language models (LLMs) with human preferences. However, traditional RM training, which relies on response pairs tied to specific prompts, struggles to disentangle prompt-driven preferences from prompt-independent artifacts, such as response length and format. In this work, we expose a fundamental limitation of current RM training methods, where RMs fail to effectively distinguish between contextual signals and irrelevant artifacts when determining preferences. To address this, we introduce a causal framework that learns preferences independent of these artifacts and propose a novel data augmentation technique designed to eliminate them. Extensive experiments show that our approach successfully filters out undesirable artifacts, yielding a more robust reward model (RRM). Our RRM improves the performance of a pairwise reward model trained on Gemma-2-9b-it, on RewardBench, increasing accuracy from 80.61% to 84.15%. Additionally, we train two DPO policies using both the RM and RRM, demonstrating that the RRM significantly enhances DPO-aligned policies, improving MT-Bench scores from 7.27 to 8.31 and length-controlled win-rates in AlpacaEval-2 from 33.46% to 52.49%.

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Cited by 9 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Test-Time Scaling via Error Localization

    cs.LG 2026-07 conditional novelty 6.0 of 10

    TTEL uses feedback-induced token probability drops to localize the first error in a failed reasoning trace and branch a new generation from that prefix, improving pass@k per token on coding and math benchmarks.

  2. Multi-Turn On-Policy Distillation with Prefix Replay

    cs.LG 2026-07 conditional novelty 6.0 of 10

    ReOPD offline-distills multi-turn agentic LLMs via teacher-prefix replay plus step-decay sampling, matching online OPD accuracy at ≥4× speed with zero tool calls.

  3. Encouraging Good Processes Without the Need for Good Answers: Reinforcement Learning for LLM Agent Planning

    cs.LG 2025-08 conditional novelty 6.0 of 10

    Decoupling LLM-agent planning from summarization and rewarding tool-call completeness rather than final-answer correctness improves planning by 8-12% and end-to-end answers by 5-6% over end-to-end RL baselines.

  4. Learning a Pessimistic Reward Model in RLHF

    cs.LG 2025-05 reject novelty 6.0 of 10

    Pessimistic fine-tuning of reward models against rejection-sampling policies lets RLHF agents optimize greedily without KL regularization and still avoid reward hacking.

  5. Think-RM: Enabling Long-Horizon Reasoning in Generative Reward Models

    cs.LG 2025-05 conditional novelty 6.0 of 10

    A generative reward model trained with long chain-of-thought and rule-based RL outperforms standard and vertically scaled reward baselines on RM-Bench and RewardBench.

  6. Causal Reward Adjustment: Mitigating Reward Hacking in External Reasoning via Backdoor Correction

    cs.LG 2025-08 unverdicted novelty 5.0 of 10

    CRA trains sparse autoencoders on PRM activations and applies backdoor adjustment to estimate true rewards, reducing reward hacking in math reasoning.

  7. MARS: Margin and Semantic-Aware Data Augmentation for Reward Modeling

    cs.LG 2026-02 reject novelty 4.0 of 10

    Concentrating synthetic preference paraphrases on low-margin pairs gives consistent but small reward-model and alignment gains in single-run experiments, while the abstract's semantic-aware, multi-benchmark claims are...

  8. Alignment and Safety in Large Language Models: Safety Mechanisms, Training Paradigms, and Emerging Challenges

    cs.AI 2025-07 reject novelty 1.0 of 10

    A broad survey of LLM alignment that catalogs objectives, benchmarks, SFT/RLHF/DPO methods, and safety challenges, without contributing new experimental or theoretical results.

  9. Inverse Reinforcement Learning Meets Large Language Model Post-Training: Basics, Advances, and Opportunities

    cs.LG 2025-07 unverdicted novelty 1.0 of 10

    A tutorial reviewing LLM alignment through the lens of inverse reinforcement learning, arguing that neural reward models learned from human data are central to post-training.

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