The Explainability Illusion: ViT patch heatmaps are a training artifact, not model property

ziv_ravid · x · 2026-10-20

A Technion paper by Schaffer, Manor and Michaeli shows that patch-token explainability in Vision Transformers — decoding individual patch tokens (à la Logit Lens) into human-interpretable heatmaps — is not an inherent property of the architecture. Whether a heatmap highlights the object, the background, or nothing at all depends on training data and sometimes even the random seed. Across architectures, scales and objectives, some ViTs show aligned token decodings while others show inverted maps or no semantic correlation at all. Theory backs this up: a single fixed toy transformer can provably implement the optimal classifier in multiple ways with different explainability patterns. The takeaway: you can't assume patch-decoding interpretability a priori — much of what's called interpretability may be reading tea leaves.

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