Process Rewards Boost Small Language Models' Math Reasoning

Anagha Radhakrishna Palandye, Rebecca Glick, Osheen Kaul· July 7, 2026 View original

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Summary

This study investigates the impact of reward granularity in Reinforcement Learning with Verifiable Rewards (RLVR) for mathematical reasoning in small language models. It finds that process-level supervision, rewarding intermediate steps, significantly improves accuracy and reasoning trace fidelity compared to only rewarding the final outcome.

Reinforcement Learning with Verifiable Rewards (RLVR) is a promising method for enhancing language models' mathematical reasoning abilities. However, most current RLVR approaches primarily reward only the final answer, neglecting the potential benefits of supervising intermediate steps. This research systematically compares different reward structures, including process-only, outcome-only, and hybrid approaches, specifically for smaller language models like Qwen2.5-0.5B. The findings reveal a substantial advantage for process-only supervision, which achieved nearly a 10-percentage point higher test accuracy on the GSM8K dataset compared to outcome-only rewards. Process-supervised models also produced more valid and consistent reasoning traces. The study highlights that reward granularity is a critical design choice for RLVR, especially for smaller models that benefit significantly from detailed, step-by-step feedback.

Why it matters

For professionals developing or deploying AI, understanding how to effectively train smaller, more efficient language models for complex tasks like mathematical reasoning is crucial. This research provides insights into optimizing reward mechanisms to achieve better performance and interpretability with limited model capacity.

How to implement this in your domain

  1. 1Analyze current fine-tuning strategies for small language models, particularly for tasks requiring multi-step reasoning.
  2. 2Design reward functions that provide feedback on intermediate steps (process rewards) rather than solely on final outcomes.
  3. 3Experiment with different weighting schemes for hybrid process and outcome rewards to find optimal configurations.
  4. 4Implement detailed error analysis using larger models (e.g., GPT-4o) to understand failure modes and refine reward strategies.
  5. 5Apply process-level supervision to improve the fidelity and accuracy of reasoning traces in custom small language models.

Who benefits

EdTechSoftware DevelopmentAI ResearchData Science

Key takeaways

  • Process-level rewards significantly improve mathematical reasoning in small language models.
  • Rewarding intermediate steps leads to higher accuracy and more faithful reasoning traces.
  • Reward granularity is a first-order design decision in RLVR, especially for smaller models.
  • Hybrid reward strategies require careful weighting to avoid conflicting optimization signals.

Original post by Anagha Radhakrishna Palandye, Rebecca Glick, Osheen Kaul

"arXiv:2607.02869v1 Announce Type: new Abstract: Reinforcement Learning with Verifiable Rewards (RLVR) has emerged as a promising paradigm for improving mathematical reasoning in language models. Yet most RLVR work rewards only the final answer (outcome-based rewards), leaving the…"

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Originally posted by Anagha Radhakrishna Palandye, Rebecca Glick, Osheen Kaul on X · view source

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