Mask What Matters: Mitigating Object Hallucinations in Multimodal Large Language Models with Object-Aligned Visual Contrastive Decoding

Boqi Chen, Xudong Liu, Jianing Qiu


Abstract
We study object hallucination in Multimodal Large Language Models (MLLMs) and improve visual contrastive decoding (VCD) by constructing an object-aligned auxiliary view. We leverage object-centric attention in self-supervised Vision Transformers. In particular, we remove the most salient visual evidence to construct an auxiliary view that disrupts unsupported tokens and produces a stronger contrast signal. Our method is prompt-agnostic, model-agnostic, and can be seamlessly plugged into the existing VCD pipeline with little computation overhead, i.e., a single cacheable forward pass. Empirically, our method demonstrates consistent gains on two popular object hallucination benchmarks across two MLLMs.
Anthology ID:
2026.eacl-srw.2
Volume:
Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 4: Student Research Workshop)
Month:
March
Year:
2026
Address:
Rabat, Morocco
Editors:
Selene Baez Santamaria, Sai Ashish Somayajula, Atsuki Yamaguchi
Venue:
EACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
9–16
Language:
URL:
https://preview.aclanthology.org/ingest-eacl/2026.eacl-srw.2/
DOI:
Bibkey:
Cite (ACL):
Boqi Chen, Xudong Liu, and Jianing Qiu. 2026. Mask What Matters: Mitigating Object Hallucinations in Multimodal Large Language Models with Object-Aligned Visual Contrastive Decoding. In Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 4: Student Research Workshop), pages 9–16, Rabat, Morocco. Association for Computational Linguistics.
Cite (Informal):
Mask What Matters: Mitigating Object Hallucinations in Multimodal Large Language Models with Object-Aligned Visual Contrastive Decoding (Chen et al., EACL 2026)
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https://preview.aclanthology.org/ingest-eacl/2026.eacl-srw.2.pdf