Do VLMs Share Safety Neurons Across Modalities?

Jiaxuan Li, Jiahao Zhang, Duc Minh Vo, Huy H. Nguyen, Pride Kavumba, Koki Wataoka


Abstract
Vision-language models (VLMs) can comply with harmful requests delivered through images, even when their LLM backbones would refuse the same content in text. While prior work characterizes these jailbreaks empirically or at the representation level, how visual inputs perturb safety pathways at the neuron level remains uncharted. We close this gap with a causal, neuron-level analysis of safety mechanisms in 10 VLMs. We propose a two-stage detection pipeline with iterative ablation that accounts for self-repair, and introduce two modality-isolated benchmarks, ViSafe-Detect and ViSafe-Eval, which decouple visual and textual safety signals.

Our analysis reveals: (i) Text safety in VLMs is localizable: ~88 neurons (<0.01%) whose targeted ablation substantially reduces refusal. (ii) Text safety neurons constitute the dominant refusal pathway: ablating them is the only intervention that consistently and substantially reduces refusal across all models. (iii) Visual safety is high-dimensional and diffuse at the single-neuron level: text safety concentrates in ~5 subspace directions while visual safety requires ≥50. This gap holds across architectures, explaining why current alignment has not closed the visual safety gap. Project page is at: https://jiaxuan-li.github.io/vlm-safety-neuron/.

Warning: this paper may include examples of harmful content.
Anthology ID:
2026.emnlp-main.471
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
10822–10837
Language:
URL:
https://aclanthology.org/2026.emnlp-main.471/
DOI:
Bibkey:
Cite (ACL):
Jiaxuan Li, Jiahao Zhang, Duc Minh Vo, Huy H. Nguyen, Pride Kavumba, and Koki Wataoka. 2026. Do VLMs Share Safety Neurons Across Modalities?. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 10822–10837, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Do VLMs Share Safety Neurons Across Modalities? (Li et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.471.pdf