Sparse pixels on an otherwise blank canvas could steer a vision encoder into a chosen semantic basin
AspireAI community · arXiv
Vision encoders are used as semantic representations, but how embedding similarity relates to human-visible semantics thins out far from the natural-image manifold. This probe tests that regime in black-box fashion, hill-climbing sparse pixel edits on blank canvases and asking whether the edited, otherwise meaningless image can retrieve a chosen target. Across ImageNet and Flickr30k, inputs optimized toward class prompts achieved strong top-1 and top-5 targeted retrieval on OpenCLIP, and on DINOv3 inputs optimized toward class prototypes reached high target alignment and near-top prototype ranks. So both language-aligned contrastive encoders and self-supervised visual encoders share an off-manifold failure mode, and a simple blank-canvas optimization is enough to enter a target semantic basin. The practical read for anyone using these encoders is that embedding space contains structure the pixels do not, so retrieval confidence should not be treated as evidence that the image contained the meaning.
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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.