From Separation to Entanglement: Dissecting Feed-Forward Network Functional Organization in Vision–Language Models for Ancient Chinese Documents

Ruilin Liu, Dongmei Zhu, Yuting Wei, Jin Song


Abstract
While Vision-Language Models (VLMs) have demonstrated strong capabilities in general multimodal tasks, they face significant challenges in low-resource, cross-temporal settings such as ancient Chinese documents, where models must overcome complex visual noise and leverage deep linguistic priors. The functional organization of task-relevant components in existing VLMs remains understudied from a computational interpretability perspective. To address this, we introduce AncientVision-3T, an intervention-oriented diagnostic benchmark designed for mechanistic interpretability experiments on VLMs, organized across OCR, image classification, and image understanding tasks of increasing abstraction. Based on this benchmark, we propose the Ancient Chinese Target-Conditioned Gradient-based Neuron analysis framework (AC-TCGN), which identifies and validates task-relevant neurons for dissecting functional organization in general and domain-specific VLMs. Our experiments demonstrate that AC-TCGN effectively identifies neurons that are critical for model predictions. Moreover, our experimental results reveal a transition from separation to entanglement in the functional organization of decoder feed-forward networks: general VLMs show stronger task-wise separability, whereas the ancient Chinese domain-specific VLM shows greater cross-task neuron sharing and reduced task-wise separability. This suggests enhanced coupling between visual form and historical-semantic processing in ancient Chinese document image-text tasks.
Anthology ID:
2026.findings-emnlp.1095
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
23176–23189
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1095/
DOI:
Bibkey:
Cite (ACL):
Ruilin Liu, Dongmei Zhu, Yuting Wei, and Jin Song. 2026. From Separation to Entanglement: Dissecting Feed-Forward Network Functional Organization in Vision–Language Models for Ancient Chinese Documents. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 23176–23189, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Separation to Entanglement: Dissecting Feed-Forward Network Functional Organization in Vision–Language Models for Ancient Chinese Documents (Liu et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.1095.pdf