arXiv Machine Learning By Riteng Zhang, Xiaoqian Wang

Rethinking SAE Evaluation: An Atomic Interpretable Unit Framework Reveals Hidden Polysemanticity and Redundancy

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The paper introduces a new framework for evaluating sparse autoencoders (SAEs) by requiring their features to form an atomic interpretable unit basis, a coordinate system for semantically meaningful explanation. It formalizes this objective and organizes existing and new metrics, such as DAME, into a comprehensive benchmarking framework. Experiments across many SAE architectures reveal that some models appear monosemantic under current metrics yet are functionally polysemantic, with dominant features being less interpretable and more redundant.

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