IC-499ViT patch embeddings contain local semantic information beyond the [cls] token, as shown by performance degradation when restricting the output head to [cls] only or removing positional embeddings

Ian Connick Covert, Tony Sun, James Zou, Tatsunori Hashimoto

SourceLocality Alignment Improves Vision-Language Models

The paper applies two interventions to the frozen ViT output before probing: (1) restricting the output head to only the [cls] token (or average embedding for models without one), and (2) anonymizing the ViT's output embeddings by removing learned positional embeddings and placing them in separate token positions. Both interventions degrade local probing performance, with the [cls]-only restriction causing the largest drop. This demonstrates that the patch embeddings in ViTs trained with image-level supervision (e.g., CLIP, IN1K) do carry useful local semantic information, rather than all information being collapsed into the [cls] token. However, the information is not perfectly organized for local prediction, which is why locality alignment still provides gains.

Evidence
interventional
Caveat
The interventions modify the probe's access to the ViT output rather than the ViT weights themselves. The paper does not report exact numerical values for the intervention results in the text; they are shown only in Figure 9 (right).
Model
CLIP / CLIP-ViT (LC), ViT IN1K ViT, MAE, DINOv2, SigLIP
Concepts
Linear representation
Datasets
MS COCO / COCO / COCO 2014 / COCO 2017 / COCO 20k / COCO-it / COCO-wl [eval]
Extraction
automatic-extraction