arXiv:2608.30720cs.LG2026-09

给变压器的表示加噪声,让相似性变统计可区分,更贴近实际功能表现。

Tracing distinguishability through transformer processing with stochastic LayerNorm

论文配图:Tracing distinguishability through transformer processing with stochastic LayerNorm
图 1 · 摘自论文原文
  • 在LayerNorm中加入高斯噪声并重归一化,使表示带体积,实现统计可区分
  • 用巴氏系数追踪扰动在深层传播,发现视觉扰动随深度持续传递
  • 揭示注意力头对特定词元差异的敏感性,适合关注模型内部机制的研究者

表征相似性是深度网络分析的基础,但点状表征间的距离未必与下游功能相关:相近状态可能产生不同行为,而相距较远的状态却可能表现一致。本文将表征赋予体积,将相似性转化为统计可区分性。重叠的随机表示必然导致下游分布重叠,使潜在比较与模型功能挂钩,并可应用信息论工具(如数据处理不等式)。我们在预训练变压器中通过轻量级修改实现该思想:每次读取残差流时,先归一化,添加各向同性高斯噪声,再重新归一化。微调阶段,每个残差流读取点学习一个分配参数,将固定的全局速率预算分配到处理堆栈中。最终模型可视为在共享全局速率预算下,以学习到的有限精度读取残差流的变压器块。利用巴氏系数,我们追踪了反事实差异在MLP块或各个注意力头的查询、键、值计算中的保留或选择性暴露。在ViT-S和GPT-2 small上的实验显示,连续视觉扰动在深层传播,且注意力头对与已知注意力模式一致的词元差异表现出特定敏感性。这些结果确立了可区分性作为功能性驱动的变压器计算视角,补充了现有可解释性方法。

原文摘要 · Abstract (English)

Representational similarity is foundational to analyses of deep networks, yet distances between point-valued representations are not intrinsically tied to downstream function: nearby states may produce different behaviors, while distant states may behave similarly. We instead give representations volume, turning similarity into statistical distinguishability. Overlapping stochastic representations necessarily induce overlapping downstream distributions, grounding latent comparison in model function and bringing it under information-theoretic tools such as the data-processing inequality. We realize this idea in pretrained transformers through a light-touch modification to LayerNorm: at each residual-stream read, we normalize the state, add isotropic Gaussian noise, and renormalize. During distillation fine-tuning, one learned allocation parameter per residual-stream read distributes a fixed global rate budget across the processing stack. The resulting model can be viewed as transformer blocks reading the residual stream with learned finite precision under a shared global rate budget. Using the Bhattacharyya coefficient, we trace which counterfactual distinctions are preserved through MLP blocks or selectively exposed to the query, key, and value computations of individual attention heads. Experiments on ViT-S and GPT-2 small reveal the depthwise propagation of continuous visual perturbations and head-specific sensitivity to token distinctions aligned with known attention motifs. These results establish distinguishability as a functionally grounded lens on transformer computation that complements existing interpretability approaches.

Transformer可区分性注意力机制表征分析

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