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# Logit Lens

3 related articles

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  1. arXiv

    A three-legged peacock still gets "two legs": a few in-context examples move attention off the category prior and onto the pixels

    Across five vision-centric tasks, adding labeled demonstrations to the context sharply raises accuracy on counterfactual examples that conflict with training priors while leaving prior-aligned accuracy nearly unchanged, indicating the models already have the visual capability and were being overridden by learned regularities.

  2. arXiv

    Qwen2.5-VL-7B shows a train/inference gap on 200 COCO images: target-token rank is fixed at 3,488 per step, and the language decoder, not the visual encoder, decides whether the attack lands

    Using a controlled two-stage PGD attack on 200 held-out COCO images with Qwen2.5-VL-7B-Instruct, the authors show that a targeted perturbation can drive teacher-forced training loss for a fixed target caption to near zero while free generation still produces the original correct description, localize this train/inference gap to a single autoregressive step (target-token rank fixed at exactly 3,488 of 152,064 vocabulary entries with zero variance), and trace all 28 decoder layers to show the visual encoder corrupts every image by a comparable margin while the language decoder amplifies the corrupted signal for susceptible images and actively suppresses it for resistant ones (p<0.001, rank-biserial r=0.579).

  3. arXiv

    Using OCR Heads to Verbalize Image Semantics: General Verbalization Heads and a Verbalization Lens in VLMs

    Across four vision-language models (Qwen3-VL-2B, Qwen3-VL-8B, Molmo2-7B, Llava-Next-34B), the work identifies attention heads causally necessary for OCR and shows they are general-purpose verbalization heads; summing their output-value matrices yields a verbalization lens that decodes image-token hidden states into interpretable semantic words at any layer, including layer 0, and whose pseudo-inverse provides concept vectors for editing image representations (e.g., replacing a tractor with a revolver), supporting the view that image representations are aligned with language space from early layers.

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