RewardBench 2: Advancing Reward Model Evaluation

Fuente: arXiv
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Autores principales: Malik, Saumya, Pyatkin, Valentina, Land, Sander, Morrison, Jacob, Smith, Noah A., Hajishirzi, Hannaneh, Lambert, Nathan
Formato: Preprint
Publicado: 2025
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author Malik, Saumya
Pyatkin, Valentina
Land, Sander
Morrison, Jacob
Smith, Noah A.
Hajishirzi, Hannaneh
Lambert, Nathan
author_facet Malik, Saumya
Pyatkin, Valentina
Land, Sander
Morrison, Jacob
Smith, Noah A.
Hajishirzi, Hannaneh
Lambert, Nathan
contents Reward models are used throughout the post-training of language models to capture nuanced signals from preference data and provide a training target for optimization across instruction following, reasoning, safety, and more domains. The community has begun establishing best practices for evaluating reward models, from the development of benchmarks that test capabilities in specific skill areas to others that test agreement with human preferences. At the same time, progress in evaluation has not been mirrored by the effectiveness of reward models in downstream tasks -- simpler direct alignment algorithms are reported to work better in many cases. This paper introduces RewardBench 2, a new multi-skill reward modeling benchmark designed to bring new, challenging data for accuracy-based reward model evaluation -- models score about 20 points on average lower on RewardBench 2 compared to the first RewardBench -- while being highly correlated with downstream performance. Compared to most other benchmarks, RewardBench 2 sources new human prompts instead of existing prompts from downstream evaluations, facilitating more rigorous evaluation practices. In this paper, we describe our benchmark construction process and report how existing models perform on it, while quantifying how performance on the benchmark correlates with downstream use of the models in both inference-time scaling algorithms, like best-of-N sampling, and RLHF training algorithms like proximal policy optimization.
format Preprint
id arxiv_https___arxiv_org_abs_2506_01937
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle RewardBench 2: Advancing Reward Model Evaluation
Malik, Saumya
Pyatkin, Valentina
Land, Sander
Morrison, Jacob
Smith, Noah A.
Hajishirzi, Hannaneh
Lambert, Nathan
Computation and Language
Reward models are used throughout the post-training of language models to capture nuanced signals from preference data and provide a training target for optimization across instruction following, reasoning, safety, and more domains. The community has begun establishing best practices for evaluating reward models, from the development of benchmarks that test capabilities in specific skill areas to others that test agreement with human preferences. At the same time, progress in evaluation has not been mirrored by the effectiveness of reward models in downstream tasks -- simpler direct alignment algorithms are reported to work better in many cases. This paper introduces RewardBench 2, a new multi-skill reward modeling benchmark designed to bring new, challenging data for accuracy-based reward model evaluation -- models score about 20 points on average lower on RewardBench 2 compared to the first RewardBench -- while being highly correlated with downstream performance. Compared to most other benchmarks, RewardBench 2 sources new human prompts instead of existing prompts from downstream evaluations, facilitating more rigorous evaluation practices. In this paper, we describe our benchmark construction process and report how existing models perform on it, while quantifying how performance on the benchmark correlates with downstream use of the models in both inference-time scaling algorithms, like best-of-N sampling, and RLHF training algorithms like proximal policy optimization.
title RewardBench 2: Advancing Reward Model Evaluation
topic Computation and Language
url https://arxiv.org/abs/2506.01937