arXiv:2606.27941cs.CLcs.AI2026-06中稿 · ICML

让自编码器特征自动对齐词汇表,直接命名可解释。

VASAE: Naming SAE Dictionary Directions with Vocabulary-Aligned Anchoring

论文配图:VASAE: Naming SAE Dictionary Directions with Vocabulary-Aligned Anchoring
图 1 · 摘自论文原文
  • 训练时用词汇对齐锚点,让每个特征自动关联最近的词元。
  • 在GPT-2-small中90%特征实现词汇对齐,Llama-3.1-8B达92.8%。
  • 特征名与输入词元相关,适合解释模型内部表示。

稀疏自编码器(SAE)能有效分解Transformer残差流,但其学习到的特征通常需事后命名,无法直接关联到模型的词元词汇表。本文提出词汇对齐稀疏自编码器(VASAE),通过词汇对齐锚定训练SAE特征,并为每个特征分配一个内在词元名称:即嵌入向量最接近该特征的词元字符串。在不降低重建质量的前提下,VASAE生成的词典具备词汇对齐特性。在GPT-2-small的残差流上,使用0.8阈值时,第0–10层约90%的特征实现对齐。在Llama-3.1-8B中,浅层和中层词典分别有92.8%和部分强对齐特征,而最终层对齐较弱。减去句子级平均稀疏码后,案例研究显示剩余特征名与附近输入词元高度相关。结果表明,词汇对齐锚定可在训练阶段将学习特征与内在词元名称连接,补充事后解释。

原文摘要 · Abstract (English)

Sparse autoencoders (SAEs) provide useful decompositions of Transformer residual streams, but their learned features are usually named post hoc rather than directly connected to the Transformer's token vocabulary. We introduce Vocabulary-Aligned Sparse Autoencoder (VASAE), a method that trains SAE features under vocabulary-aligned anchoring and assigns each feature an intrinsic token name: the token string whose embedding is nearest to that feature. Without reducing reconstruction quality compared with a standard SAE, VASAE produces dictionaries with vocabulary-aligned features. Using a 0.8 cutoff on the nearest-token alignment score, dictionaries trained on GPT-2-small post-residual streams align about 90% of features in layers 0--10. In Llama-3.1-8B, representative shallow and middle-layer dictionaries contain strongly aligned features, including 92.8% in the shallow layer, while the representative final-layer dictionary shows limited alignment. After subtracting the sentence-level mean sparse code, case studies show that many remaining intrinsic token names are relevant to nearby input tokens. These results suggest that vocabulary-aligned anchoring can connect learned features to intrinsic token names during training, complementing post hoc interpretation of learned dictionaries.

稀疏自编码器模型解释词元对齐Transformer

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