Self-supervised training signals kept improving while the encoder quietly lost what it had learned
AspireAI community · arXiv
Self-supervised training is usually monitored without labels, through the loss and statistics of the learned features. This paper builds a case where the ground truth is known: LeJEPA encoders were trained on synthetic images with known generating factors, so a genuine degradation can be checked. In nine of ten seeds the readability of those factors fell abruptly and stayed down, nearly always along the same direction in factor space. Meanwhile the loss kept falling, and most of the eleven label-free signals tracked kept improving and rated the declining runs better than runs that did not decline. Standard change-point detection rarely flagged the decline near its onset, and selecting checkpoints by those signals mostly picked ones after it. The scope is narrow, synthetic and self-supervised, but it is a concrete warning that the usual no-label monitoring curves can be actively misleading.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.