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arXiv 2405.08366cs.LG

迈向对用于可解释性与控制的稀疏自编码器的原则性评估

Towards Principled Evaluations of Sparse Autoencoders for Interpretability and Control

Aleksandar Makelov, George Lange, Neel Nanda

AI总结:

本文提出以有监督特征字典为参照,在具体任务中从近似、控制和可解释性三维度评估 SAE,并在 GPT-2 Small 的 IOI 任务中揭示其控制局限及特征遮蔽、过度分裂现象。

摘要:

将模型激活解耦为有意义的特征是可解释性中的一个核心问题。然而,在现实场景中,这些特征缺乏真值,使得验证稀疏字典学习等近期方法变得困难。为应对这一挑战,我们提出一个在特定任务情境下评估特征字典的框架,方法是将它们与“有监督”特征字典进行比较。首先,我们证明有监督字典能够在该任务上对模型计算实现出色的近似、控制和可解释性。其次,我们使用有监督字典,沿着相同的三个维度来开发并情境化对无监督字典的评估。我们使用 GPT-2 Small 将该框架应用于间接宾语识别(IOI)任务,其中稀疏自编码器(SAE)分别在 IOI 或 OpenWebText 数据集上训练。我们发现,这些 SAE 捕获了 IOI 任务的可解释特征,但在控制模型方面不如有监督特征成功。最后,我们在 SAE 训练中观察到两种定性现象:特征遮蔽,即一个具有因果相关性的概念在所学特征中被哪怕幅度略高的特征稳定地掩盖;以及特征过度分裂,即二元特征分裂成许多更小、更不可解释的特征。我们希望本框架能为更客观、更有依据地评估稀疏字典学习方法迈出有用的一步。

英文摘要:

Disentangling model activations into meaningful features is a central problem in interpretability. However, the absence of ground-truth for these features in realistic scenarios makes validating recent approaches, such as sparse dictionary learning, elusive. To address this challenge, we propose a framework for evaluating feature dictionaries in the context of specific tasks, by comparing them against \emph{supervised} feature dictionaries. First, we demonstrate that supervised dictionaries achieve excellent approximation, control, and interpretability of model computations on the task. Second, we use the supervised dictionaries to develop and contextualize evaluations of unsupervised dictionaries along the same three axes. We apply this framework to the indirect object identification (IOI) task using GPT-2 Small, with sparse autoencoders (SAEs) trained on either the IOI or OpenWebText datasets. We find that these SAEs capture interpretable features for the IOI task, but they are less successful than supervised features in controlling the model. Finally, we observe two qualitative phenomena in SAE training: feature occlusion (where a causally relevant concept is robustly overshadowed by even slightly higher-magnitude ones in the learned features), and feature over-splitting (where binary features split into many smaller, less interpretable features). We hope that our framework will provide a useful step towards more objective and grounded evaluations of sparse dictionary learning methods.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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