# DelTA：基于可验证奖励强化学习的判别性Token信用分配

- 来源：HuggingFace Daily Papers（社区热门论文）
- 发布时间：2026-05-20 08:00
- AIHOT 分数：64
- AIHOT 链接：https://aihot.virxact.com/items/cmpgeo9hw0esjsljw8gq029td
- 原文链接：https://arxiv.org/abs/2605.21467

## AI 摘要

可验证奖励强化学习是提升大语言模型推理能力的关键技术，但奖励信号如何转化为token级概率变化的机制尚不明确。本文提出判别器视角，揭示策略梯度更新方向本质上是区分不同奖励响应的线性判别器。现有方法的正负侧质心易被格式化token等高频模式主导，稀释了关键判别信息。为此，我们提出DelTA方法，通过估计token系数来重塑更新方向，放大特定侧梯度并削弱共享模式权重。实验表明，DelTA在多项数学基准上显著提升了模型性能，并在代码生成与跨域任务中展现出良好的泛化能力。

## 正文

Reinforcement learning from verifiable rewards (RLVR) has emerged as a central technique for improving the reasoning capabilities of large language models. Despite its effectiveness, how response-level rewards translate into token-level probability changes remains poorly understood. We introduce a discriminator view of RLVR updates, showing that the policy-gradient update direction implicitly acts as a linear discriminator over token-gradient vectors and thereby determines which token probabilities are increased or decreased during learning. Under standard sequence-level RLVR, this discriminator is constructed from positive- and negative-side centroids formed by advantage-weighted averaging of token-gradient vectors. However, such centroid construction can be dominated by shared high-frequency patterns, such as formatting tokens, diluting sparse yet discriminative directions that better distinguish high-reward responses from low-reward ones. To address this limitation, we propose DelTA, a discriminative token credit assignment method that estimates token coefficients to amplify side-specific token-gradient directions and downweight shared or weakly discriminative ones. These coefficients reweight a self-normalized RLVR surrogate, making the effective side-wise centroids more contrastive and thereby reshaping the RLVR update direction. On seven mathematical benchmarks, DelTA outperforms the strongest same-scale baselines by 3.26 and 2.62 average points on Qwen3-8B-Base and Qwen3-14B-Base, respectively. Additional results on code generation, a different backbone, and out-of-domain evaluations further demonstrate the generalization ability of DelTA.