为决策Transformer引入动作记忆,提升在线学习效率。
Mental Accounts for Actions: EWA-Inspired Attention in Decision Transformers
- 用向量量化构建动作专属心理账户,记录近期成败
- 在连续控制任务中早期训练即显著提升采样效率与回报
- 轻量模块无需修改主干,可解释性强且理论保障
Transformer在序列决策中通过自注意力建模轨迹,使强化学习可无价值函数近似地进行回报条件控制。决策变压器(DT)将强化学习视为监督序列建模,但受限于离线数据且缺乏探索能力。在线决策变压器(ODT)通过策略滚动生成的熵正则化训练,提供稳定替代方案,避免传统方法依赖自举目标和奖励塑造。然而,现有方法使用标准注意力,未显式记忆动作结果,导致长期动作有效性学习低效。受经验加权吸引力(EWA)认知模型启发,本文提出基于向量量化的在线决策变压器(EWA-VQ-ODT),引入轻量模块维护每个动作的心理账户,总结近期成功与失败。连续动作通过直接网格查找映射至紧凑的向量量化码本,每个码字存储标量吸引力,并通过衰减与奖励驱动在线更新。这些吸引力通过偏置动作令牌对应的列来调节注意力,无需改动主干或训练目标。在标准连续控制基准测试中,该方法在早期训练阶段即显著提升样本效率与平均回报。模块计算高效,可通过每码追踪实现可解释性,并具备吸引力动态及其对注意力漂移影响的理论边界保证。
原文摘要 · Abstract (English)
Transformers have emerged as a compelling architecture for sequential decision-making by modeling trajectories via self-attention. In reinforcement learning (RL), they enable return-conditioned control without relying on value function approximation. Decision Transformers (DTs) exploit this by casting RL as supervised sequence modeling, but they are restricted to offline data and lack exploration. Online Decision Transformers (ODTs) address this limitation through entropy-regularized training on on-policy rollouts, offering a stable alternative to traditional RL methods like Soft Actor-Critic, which depend on bootstrapped targets and reward shaping. Despite these advantages, ODTs use standard attention, which lacks explicit memory of action-specific outcomes. This leads to inefficiencies in learning long-term action effectiveness. Inspired by cognitive models such as Experience-Weighted Attraction (EWA), we propose Experience-Weighted Attraction with Vector Quantization for Online Decision Transformers (EWA-VQ-ODT), a lightweight module that maintains per-action mental accounts summarizing recent successes and failures. Continuous actions are routed via direct grid lookup to a compact vector-quantized codebook, where each code stores a scalar attraction updated online through decay and reward-based reinforcement. These attractions modulate attention by biasing the columns associated with action tokens, requiring no change to the backbone or training objective. On standard continuous-control benchmarks, EWA-VQ-ODT improves sample efficiency and average return over ODT, particularly in early training. The module is computationally efficient, interpretable via per-code traces, and supported by theoretical guarantees that bound the attraction dynamics and its impact on attention drift.
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