A Comprehensive Survey of Reward Models:
Taxonomy, Applications, Challenges, and Future
Jialun Zhong1,4∗,
Wei Shen2∗,
Yanzeng Li1,
Songyang Gao2,
Hua Lu3,
Yicheng Chen4,
Yang Zhang4,
Jinjie Gu4,
Wei Zhou4,
Lei Zou1†
1Peking University
2Fudan University
3Huazhong University of Science and Technology
4Ant Group
😄 Welcome to recommend missing papers through Issues and Pull Requests.
Paper List
🔍 Preference Collection
Human Preference
- Deep Reinforcement Learning from Human Preferences
2017 [NeurIPS]
- Batch Active Preference-Based Learning of Reward Functions
2018 [CoRL]
- Reward learning from human preferences and demonstrations in Atari
2018 [NeurIPS]
- Active Preference-Based Gaussian Process Regression for Reward Learning
2020 [RSS]
- Information Directed Reward Learning for Reinforcement Learning
2021 [NeurIPS]
- PEBBLE: Feedback-Efficient Interactive Reinforcement Learning via Relabeling Experience and Unsupervised Pre-training
2021 [ICML]
- Improving alignment of dialogue agents via targeted human judgements
2022 [arxiv]
- Training language models to follow instructions with human feedback
2022 [NeurIPS]
- SURF: Semi-supervised Reward Learning with Data Augmentation for Feedback-efficient Preference-based Reinforcement Learning
2022 [ICLR]
- Training a Helpful and Harmless Assistant with Reinforcement Learning from Human Feedback
2022 [arxiv]
- Active Reward Learning from Multiple Teachers
2023 [AAAI Workshop]
- RLHF-Blender: A Configurable Interactive Interface for Learning from Diverse Human Feedback
2023 [ICML Workshop]
- Sequential Preference Ranking for Efficient Reinforcement Learning from Human Feedback
2023 [NeurIPS]
- Fine-Grained Human Feedback Gives Better Rewards for Language Model Training
2023 [NeurIPS]
- Uni-RLHF: Universal Platform and Benchmark Suite for Reinforcement Learning with Diverse Human Feedback
2024 [ICLR]
- HelpSteer2: Open-source dataset for training top-performing reward models
2024 [arxiv]
- Batch Active Learning of Reward Functions from Human Preferences
2024 [arxiv]
- Towards Comprehensive Preference Data Collection for Reward Modeling
2024 [arxiv]
- RLHF Workflow: From Reward Modeling to Online RLHF
2024 [TMLR]
- Towards Comprehensive Preference Data Collection for Reward Modeling
2024 [arxiv]
- Preference Fine-Tuning of LLMs Should Leverage Suboptimal, On-Policy Data
2024 [arxiv]
- Less is More: Improving LLM Alignment via Preference Data Selection
2025 [arxiv]
- RLTHF: Targeted Human Feedback for LLM Alignment
2025 [arxiv]
AI Preference
- Constitutional AI: Harmlessness from AI Feedback
2022 [arxiv]
- AlpacaFarm: A Simulation Framework for Methods that Learn from Human Feedback
2023 [NeurIPS]
- Aligning Large Language Models through Synthetic Feedback
2023 [EMNLP]
- RLAIF vs. RLHF: Scaling Reinforcement Learning from Human Feedback with AI Feedback
2024 [ICML]
- UltraFeedback: Boosting Language Models with Scaled AI Feedback
2024 [ICML]
- SALMON: Self-Alignment with Instructable Reward Models
2024 [ICLR]
- Improving Reward Models with Synthetic Critiques
2024 [arxiv]
- Self-Generated Critiques Boost Reward Modeling for Language Models
2024 [arxiv]
- Safer-Instruct: Aligning Language Models with Automated Preference Data
2024 [NAACL]
- Negating Negatives: Alignment with Human Negative Samples via Distributional Dispreference Optimization
2024 [EMNLP Findings]
- RLCD: Reinforcement Learning from Contrastive Distillation for LM Alignment
2024 [ICLR]
- West-of-N: Synthetic Preference Generation for Improved Reward Modeling
2024 [ICLR Workshop]
- RMBoost: Reward Model Training With Preference-Conditional Multi-Aspect Synthetic Data Generation
2025 [ICLR Workshop]
- Interpreting Language Model Preferences Through the Lens of Decision Trees
2025 [Online]
🖥️ Reward Modeling
Type-Level
Discriminative Reward
- LLM-Blender: Ensembling Large Language Models with Pairwise Ranking and Generative Fusion
2023 [ACL]
- InternLM2 Technical Report
2024 [arxiv]
- Advancing LLM Reasoning Generalists with Preference Trees
2024 [arxiv]
- Regularizing Hidden States Enables Learning Generalizable Reward Model for LLMs
2024 [NeurIPS]
- MetaMetrics: Calibrating Metrics For Generation Tasks Using Human Preferences
2024 [ICLR]
- Nemotron-4 340B Technical Report
2024 [arxiv]
- Interpretable Preferences via Multi-Objective Reward Modeling and Mixture-of-Experts
2024 [arxiv]
Generative Reward
- Judging LLM-as-a-Judge with MT-Bench and Chatbot Arena
2023 [NeurIPS]
- Generative Judge for Evaluating Alignment
2024 [ICLR]
- Prometheus 2: An Open Source Language Model Specialized in Evaluating Other Language Models
2024 [EMNLP]
- CompassJudger-1: All-in-one Judge Model Helps Model Evaluation and Evolution
2024 [arxiv]
- LLM Critics Help Catch LLM Bugs
2024 [arxiv]
- LLM Critics Help Catch Bugs in Mathematics: Towards a Better Mathematical Verifier with Natural Language Feedback
2024 [arxiv]
- Meta-Rewarding Language Models: Self-Improving Alignment with LLM-as-a-Meta-Judge
2024 [arxiv]
- Self-Taught Evaluators
2024 [arxiv]
- Self-Rewarding Language Models
2024 [ICML]
- Direct Judgement Preference Optimization
2024 [arxiv]
- Generative Reward Models
2024 [arxiv]
- Generative Verifiers: Reward Modeling as Next-Token Prediction
2024 [arxiv]
- Beyond Scalar Reward Model: Learning Generative Judge from Preference Data
2024 [arxiv]
- Improving Large Language Models via Fine-grained Reinforcement Learning with Minimum Editing Constraint
2024 [ACL Findings]
Implicit Reward
- Direct Preference Optimization: Your Language Model is Secretly a Reward Model
2023 [NeurIPS]
- SLiC-HF: Sequence Likelihood Calibration with Human Feedback
2023 [arxiv]
- A General Theoretical Paradigm to Understand Learning from Human Preferences
2023 [arxiv]
- A Minimaximalist Approach to Reinforcement Learning from Human Feedback
2024 [ICML]
- Smaug: Fixing Failure Modes of Preference Optimisation with DPO-Positive
2024 [arxiv]
- From $r$ to $Q^*$: Your Language Model is Secretly a Q-Function
2024 [COLM]
- Step-DPO: Step-wise Preference Optimization for Long-chain Reasoning of LLMs
2024 [arxiv]
- Token-level Direct Preference Optimization
2024 [ICML]
- $β$-DPO: Direct Preference Optimization with Dynamic $β$
2024 [NeurIPS]
- Generalized Preference Optimization: A Unified Approach to Offline Alignment
2024 [ICML]
- Contrastive Preference Optimization: Pushing the Boundaries of LLM
2024 [ICML]
- Offline Regularised Reinforcement Learning for Large Language Models Alignment
2024 [arxiv]
- Direct Nash Optimization: Teaching Language Models to Self-Improve with General Preferences
2024 [arxiv]
- ORPO: Monolithic Preference Optimization without Reference Model
2024 [EMNLP]
- Mixed Preference Optimization: A Two-stage Reinforcement Learning with Human Feedbacks
2024 [arxiv]
- LiPO: Listwise Preference Optimization through Learning-to-Rank
2024 [arxiv]
- Noise Contrastive Alignment of Language Models with Explicit Rewards
2024 [NeurIPS]
- SimPO: Simple Preference Optimization with a Reference-Free Reward
2024 [NeurIPS]
- Direct Preference Optimization with an Offset
2024 [ACL Findings]
- Statistical Rejection Sampling Improves Preference Optimization
2024 [ICLR]
- sDPO: Don’t Use Your Data All at Once
2025 [COLING Industry]
- Towards Robust Alignment of Language Models: Distributionally Robustifying Direct Preference Optimization
2025 [ICLR]
- Self-Play Preference Optimization for Language Model Alignment
2025 [ICLR]
- TIS-DPO: Token-level Importance Sampling for Direct Preference Optimization With Estimated Weights
2025 [ICLR]
Granularity-Level
Outcome Reward
TBD
Process Reward
- Solving math word problems with process- and outcome-based feedback
2022 [arxiv]
- GRACE: Discriminator-Guided Chain-of-Thought Reasoning
2023 [EMNLP Findings]
- Making Language Models Better Reasoners with Step-Aware Verifier
2023 [ACL]
- Let's reward step by step: Step-Level reward model as the Navigators for Reasoning
2023 [arxiv]
- Let’s Reinforce Step by Step
2023 [NeurIPS Workshop]
- Math-Shepherd: Verify and Reinforce LLMs Step-by-step without Human Annotations
2024 [ACL]
- Multi-step Problem Solving Through a Verifier: An Empirical Analysis on Model-induced Process Supervision
2024 [EMNLP Findings]
- Improve Mathematical Reasoning in Language Models by Automated Process Supervision
2024 [arxiv]
- Let's Verify Step by Step
2024 [ICLR]
- AutoPSV: Automated Process-Supervised Verifier
2024 [NeurIPS]
- Process Reward Model with Q-value Rankings
2025 [ICLR]
- Rewarding Progress: Scaling Automated Process Verifiers for LLM Reasoning
2025 [ICLR]
- Process Reinforcement through Implicit Rewards
2025 [arxiv]
- The Lessons of Developing Process Reward Models in Mathematical Reasoning
2025 [arxiv]
- AdaptiveStep: Automatically Dividing Reasoning Step through Model Confidence
2025 [arxiv]
- Better Process Supervision with Bi-directional Rewarding Signals
2025 [arxiv]
- An Efficient and Precise Training Data Construction Framework for Process-supervised Reward Model in Mathematical Reasoning
2025 [arxiv]
- VersaPRM: Multi-Domain Process Reward Model via Synthetic Reasoning Data
2025 [arxiv]
🦾 Usages
Data Selection
- RAFT: Reward rAnked FineTuning for Generative Foundation Model Alignment
2023 [TMLR]
- RRHF: Rank Responses to Align Language Models with Human Feedback without tears
2023 [NeurIPS]
- Reinforced Self-Training (ReST) for Language Modeling
2023 [arxiv]
- Iterative Reasoning Preference Optimization
2024 [NeruIPS]
- Filtered Direct Preference Optimization
2024 [EMNLP]
Policy Training
- Fine-Grained Human Feedback Gives Better Rewards for Language Model Training
2023 [NeurIPS]
- Aligning Crowd Feedback via Distributional Preference Reward modeling
2024 [arxiv]
- Reward-Robust RLHF in LLMs
2024 [arxiv]
- Bayesian Reward Models for LLM Alignment
2024 [arxiv]
- Prior Constraints-based Reward Model Training for Aligning Large Language Models
2024 [CCL]
- ODIN: Disentangled Reward Mitigates Hacking in RLHF
2024 [ICML]
- Disentangling Length from Quality in Direct Preference Optimization
2024 [ACL Findings]
- WARM: On the Benefits of Weight Averaged Reward Models
2024 [ICML]
- Improving Reinforcement Learning from Human Feedback with Efficient Reward Model Ensemble
2024 [arxiv]
- RRM: Robust Reward Model Training Mitigates Reward Hacking
2025 [ICLR]
- Beyond Reward Hacking: Causal Rewards for Large Language Model Alignment
2025 [arxiv]
Inference
- Let's reward step by step: Step-Level reward model as the Navigators for Reasoning
2023 [arxiv]
- ReST-MCTS*: LLM Self-Training via Process Reward Guided Tree Search
2024 [arxiv]
- Advancing Process Verification for Large Language Models via Tree-Based Preference Learning
2024 [arxiv]
- Rewarding Progress: Scaling Automated Process Verifiers for LLM Reasoning
2025 [ICLR]
- Process Reward Models for LLM Agents: Practical Framework and Directions
2025 [arxiv]
- Reward-Guided Speculative Decoding for Efficient LLM Reasoning
2025 [arxiv]
🛠️ Applications
Harmless Dialogue
Dialogue
- Training a Helpful and Harmless Assistant with Reinforcement Learning from Human Feedback
2022 [arxiv]
- Constitutional AI: Harmlessness from AI Feedback
2022 [arxiv]
- Zhongjing: Enhancing the Chinese Medical Capabilities of Large Language Model through Expert Feedback and Real-world Multi-turn Dialogue
2023 [arxiv]
- HuatuoGPT, Towards Taming Language Models To Be a Doctor
2023 [EMNLP Findings]
- Empathy Level Alignment via Reinforcement Learning for Empathetic Response Generation
2024 [arxiv]
- RLAIF vs. RLHF: Scaling Reinforcement Learning from Human Feedback with AI Feedback
2024 [ICML]
- Safe RLHF: Safe Reinforcement Learning from Human Feedback
2024 [ICLR]
- Deliberative Alignment: Reasoning Enables Safer Language Models
2024 [arxiv]
- Training Dialogue Systems by AI Feedback for Improving Overall Dialogue Impression
2025 [arxiv]
Logical Reasoning
Math
- Training Verifiers to Solve Math Word Problems
2022 [arxiv]
- Solving math word problems with process- and outcome-based feedback
2022 [arxiv]
- WizardMath: Empowering Mathematical Reasoning for Large Language Models via Reinforced Evol-Instruct
2023 [arxiv]
- Let's Verify Step by Step
2024 [ICLR]
- DeepSeekMath: Pushing the Limits of Mathematical Reasoning in Open Language Models
2024 [arxiv]
- Improve Mathematical Reasoning in Language Models by Automated Process Supervision
2024 [arxiv]
- Math-Shepherd: Verify and Reinforce LLMs Step-by-step without Human Annotations
2024 [ACL]
- The Lessons of Developing Process Reward Models in Mathematical Reasoning
2025 [arxiv]
- Retrieval-Augmented Process Reward Model for Generalizable Mathematical Reasoning
2025 [arxiv]
Code
- Let's reward step by step: Step-Level reward model as the Navigators for Reasoning
2023 [arxiv]
- Applying RLAIF for Code Generation with API-usage in Lightweight LLMs
2024 [arxiv]
- Process Supervision-Guided Policy Optimization for Code Generation
2024 [arxiv]
- Performance-Aligned LLMs for Generating Fast Code
2024 [arxiv]
- Policy Filtration in RLHF to Fine-Tune LLM for Code Generation
2024 [arxiv]
- LLM Critics Help Catch LLM Bugs
2024 [arxiv]
Retrieve & Recommendation
Retrieve
- Enhancing Generative Retrieval with Reinforcement Learning from Relevance Feedback
2023 [EMNLP]
- When Search Engine Services meet Large Language Models: Visions and Challenges
2024 [arxiv]
- Syntriever: How to Train Your Retriever with Synthetic Data from LLMs
2025 [arxiv]
- RAG-Gym: Optimizing Reasoning and Search Agents with Process Supervision
2025 [arxiv]
- DeepRAG: Thinking to Retrieval Step by Step for Large Language Models
2025 [arxiv]
Recommendation
- Reinforcement Learning-based Recommender Systems with Large Language Models for State Reward and Action Modeling
2024 [SIGIR]
- RLRF4Rec: Reinforcement Learning from Recsys Feedback for Enhanced Recommendation Reranking
2024 [arxiv]
- Fine-Tuning Large Language Model Based Explainable Recommendation with Explainable Quality Reward
2025 [AAAI]
Other Applications
Text to Audio
- MusicRL: Aligning Music Generation to Human Preferences
2024 [ICML]
- BATON: Aligning Text-to-Audio Model Using Human Preference Feedback
2024 [IJCAI]
- Reinforcement Learning for Fine-tuning Text-to-speech Diffusion Models
2024 [arxiv]
Text to Image
- Aligning Text-to-Image Models using Human Feedback
2023 [arxiv]
- ImageReward: Learning and Evaluating Human Preferences for Text-to-Image Generation
2023 [NeurIPS]
- DPOK: Reinforcement Learning for Fine-tuning Text-to-Image Diffusion Models]
2023 [arxiv]
Text to Video
- InstructVideo: Instructing Video Diffusion Models with Human Feedback
2024 [CVPR]
- Boosting Text-to-Video Generative Model with MLLMs Feedback
2024 [NeurIPS]
- Harness Local Rewards for Global Benefits: Effective Text-to-Video Generation Alignment with Patch-level Reward Models
2025 [arxiv]
Robotic
- Efficient Preference-Based Reinforcement Learning Using Learned Dynamics Models
2023 [ICRA]
- Accelerating Reinforcement Learning of Robotic Manipulations via Feedback from Large Language Models
2023 [arxiv]
- Vision-Language Models are Zero-Shot Reward Models for Reinforcement Learning
2024 [ICLR]
Game
- DIP-RL: Demonstration-Inferred Preference Learning in Minecraft
2025 [arxiv]
- Process Reward Models for LLM Agents: Practical Framework and Directions
2025 [arxiv]
💯 Evaluation
Benchmarks
- RewardBench: Evaluating Reward Models for Language Modeling
2024 [arxiv] [Leaderboard]
- RM-Bench: Benchmarking Reward Models of Language Models with Subtlety and Style
2024 [arxiv]
- RMB: comprehensively benchmarking reward models in LLM alignment
2024 [arxiv]
- VL-RewardBench: A Challenging Benchmark for Vision-Language Generative Reward Models
2024 [arxiv] [Leaderboard]
- How to Evaluate Reward Models for RLHF
2024 [arxiv] [Leaderboard]
- ProcessBench: Identifying Process Errors in Mathematical Reasoning
2024 [arxiv]
- RAG-RewardBench: Benchmarking Reward Models in Retrieval Augmented Generation for Preference Alignment
2024 [arxiv]
- M-RewardBench: Evaluating Reward Models in Multilingual Settings
2024 [arxiv]
- MJ-Bench: Is Your Multimodal Reward Model Really a Good Judge for Text-to-Image Generation?
2024 [arxiv] [Leaderboard]
- PRMBench: A Fine-grained and Challenging Benchmark for Process-Level Reward Models
2025 [arxiv]
- Multimodal RewardBench: Holistic Evaluation of Reward Models for Vision Language Models
2025 [arxiv]
- VLRMBench: A Comprehensive and Challenging Benchmark for Vision-Language Reward Models
2025 [arxiv]
🤺 Challenges
Data
- Fine-Tuning Language Models from Human Preferences
2019 [arxiv]
- The Expertise Problem: Learning from Specialized Feedback
2022 [arxiv]
- Active Reward Learning from Multiple Teachers
2023 [AAAI Workshop]
- Peering Through Preferences: Unraveling Feedback Acquisition for Aligning Large Language Models
2024 [ICLR]
Training
- Defining and Characterizing Reward Hacking
2022 [NeurIPS]
- A Baseline Analysis of Reward Models' Ability To Accurately Analyze Foundation Models Under Distribution Shift
2023 [arxiv]
- Scaling Laws for Reward Model Overoptimization
2023 [ICML]
- Loose lips sink ships: Mitigating Length Bias in Reinforcement Learning from Human Feedback
2023 [EMNLP Findings]
- Honesty to Subterfuge: In-Context Reinforcement Learning Can Make Honest Models Reward Hack
2024 [arxiv]
- Sycophancy to Subterfuge: Investigating Reward-Tampering in Large Language Models
2024 [arxiv]
- Language Models Learn to Mislead Humans via RLHF
2024 [arxiv]
- Towards Understanding Sycophancy in Language Models
2024 [ICLR]
- Reward Model Ensembles Help Mitigate Overoptimization
2024 [ICLR]
- Catastrophic Goodhart: regularizing RLHF with KL divergence does not mitigate heavy-tailed reward misspecification
2024 [NeurIPS]
- Spontaneous Reward Hacking in Iterative Self-Refinement
2024 [arxiv]
- Confronting Reward Model Overoptimization with Constrained RLHF
2024 [ICLR]
- Rethinking Reward Model Evaluation: Are We Barking up the Wrong Tree?
2025 [ICLR]
- Correlated Proxies: A New Definition and Improved Mitigation for Reward Hacking
2025 [ICLR]
- RRM: Robust Reward Model Training Mitigates Reward Hacking
2025 [ICLR]
- The Energy Loss Phenomenon in RLHF: A New Perspective on Mitigating Reward Hacking
2025 [arxiv]
Evaluation
- An Empirical Study of LLM-as-a-Judge for LLM Evaluation: Fine-tuned Judge Models are Task-specific Classifiers
2024 [arxiv]
- OffsetBias: Leveraging Debiased Data for Tuning Evaluators
2024 [EMNLP Findings]
- Preference Leakage: A Contamination Problem in LLM-as-a-judge
2025 [arxiv]
📊 Analysis
- The Accuracy Paradox in RLHF: When Better Reward Models Don’t Yield Better Language Models
2024 [EMNLP]
- Helping or Herding? Reward Model Ensembles Mitigate but do not Eliminate Reward Hacking
2024 [COLM]
- Rethinking Bradley-Terry Models in Preference-Based Reward Modeling: Foundations, Theory, and Alternatives
2024 [arxiv]
- RLHF Deciphered: A Critical Analysis of Reinforcement Learning from Human Feedback for LLMs
2024 [arxiv]
- Towards Analyzing and Understanding the Limitations of DPO: A Theoretical Perspective
2024 [arxiv]
- Is DPO Superior to PPO for LLM Alignment? A Comprehensive Study
2024 [ICML]
- Rethinking Reward Model Evaluation: Are We Barking up the Wrong Tree?
2025 [ICLR]
- All Roads Lead to Likelihood: The Value of Reinforcement Learning in Fine-Tuning
2025 [arxiv]
- Reward Models Identify Consistency, Not Causality
2025 [arxiv]
- What Are Step-Level Reward Models Rewarding? Counterintuitive Findings from MCTS-boosted Mathematical Reasoning
2025 [AAAI]
Resources
🌏 Blogs
- Illustrating Reinforcement Learning from Human Feedback (RLHF) [Link]
- Why reward models are key for alignment [Link]
- Reward Hacking in Reinforcement Learning [Link]
📚 Prior Survey
- A Survey on Interactive Reinforcement Learning: Design Principles and Open Challenges
2021 [arxiv]
- Reinforcement Learning With Human Advice: A Survey
2021 [Frontiers Robotics AI]
- AI Alignment: A Comprehensive Survey
2023 [arxiv]
- A Survey of Reinforcement Learning from Human Feedback
2023 [arxiv]
- Open Problems and Fundamental Limitations of Reinforcement Learning from Human Feedback
2023 [TMLR]
- Human-in-the-Loop Reinforcement Learning: A Survey and Position on Requirements, Challenges, and Opportunities
2024 [JAIR]
- Survey on Large Language Model-Enhanced Reinforcement Learning: Concept, Taxonomy, and Methods
2024 [arxiv]
- A Survey on Human Preference Learning for Large Language Models
2024 [arxiv]
- A Comprehensive Survey of LLM Alignment Techniques: RLHF, RLAIF, PPO, DPO and More
2024 [arxiv]
- Reinforcement Learning Enhanced LLMs: A Survey
2024 [arxiv]
- Towards a Unified View of Preference Learning for Large Language Models: A Survey
2024 [arxiv]
- A Survey on Post-training of Large Language Models
2025 [arxiv]