arXiv:2509.22994cs.LG2025-09

用概率采样改进稀疏自编码器,结果反而让更多特征失效。

Analysis of Variational Sparse Autoencoders

  • 用高斯后验随机采样替代确定性门控,引入变分正则化
  • 变分模型特征独立性提升,但存活特征比例下降至30%以下
  • 适合研究特征可解释性与正则化机制的学者参考

稀疏自编码器(SAE)通过从密集激活中学习稀疏、可解释的特征,成为解析神经网络表征的有力工具。本文探讨将变分方法引入SAE架构是否能提升特征组织性与可解释性。提出变分稀疏自编码器(vSAE),以从学习到的高斯后验中进行随机采样取代确定性ReLU门控,并引入向标准正态分布的KL散度正则化。假设该概率采样带来分散压力,使潜在空间中的特征更一致且不重叠。在Pythia-70M模型残差流激活上,对比TopK vSAE与标准TopK SAE,使用SAE Bench、单个特征可解释性分析及t-SNE全局可视化等综合基准评估。结果显示,vSAE在核心指标上表现逊于标准SAE,尽管在特征独立性和消融测试中表现优异。KL散度项导致过度正则化,显著降低存活特征比例,造成性能下降。虽特征鲁棒性提升,但死特征数量远超基线。研究表明,直接套用变分方法无法改善SAE的特征组织或可解释性。

原文摘要 · Abstract (English)

Sparse Autoencoders (SAEs) have emerged as a promising approach for interpreting neural network representations by learning sparse, human-interpretable features from dense activations. We investigate whether incorporating variational methods into SAE architectures can improve feature organization and interpretability. We introduce the Variational Sparse Autoencoder (vSAE), which replaces deterministic ReLU gating with stochastic sampling from learned Gaussian posteriors and incorporates KL divergence regularization toward a standard normal prior. Our hypothesis is that this probabilistic sampling creates dispersive pressure, causing features to organize more coherently in the latent space while avoiding overlap. We evaluate a TopK vSAE against a standard TopK SAE on Pythia-70M transformer residual stream activations using comprehensive benchmarks including SAE Bench, individual feature interpretability analysis, and global latent space visualization through t-SNE. The vSAE underperforms standard SAE across core evaluation metrics, though excels at feature independence and ablation metrics. The KL divergence term creates excessive regularization pressure that substantially reduces the fraction of living features, leading to observed performance degradation. While vSAE features demonstrate improved robustness, they exhibit many more dead features than baseline. Our findings suggest that naive application of variational methods to SAEs does not improve feature organization or interpretability.

稀疏自编码器变分方法可解释性神经网络

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