Learning to Search: A Decision-Based Agent for Knowledge-Based Visual Question Answering

Zhuohong Chen, ZhengXian Wu, Yunyao Yu, Hangrui Xu, Zirui Liao, Zhifang Liu, Xiangwen Deng, Peng Jiao, Haoqian Wang


Abstract
Knowledge-based visual question answering (KB-VQA) requires vision-language models to understand images and use external knowledge, especially for rare entities and long-tail facts. Most existing retrieval-augmented generation (RAG) methods adopt a fixed pipeline that sequentially retrieves information, filters it, and then produces an answer. Such a design makes it difficult to adapt to diverse question types. Moreover, it separates retrieval from reasoning, making it hard for the model to decide when to search, how to refine queries, or when to stop. As a result, the retrieved evidence is often poorly aligned with the question. To address these limitations, we reformulate KB-VQA as a search-agent problem and model the solving process as a multi-step decision-making procedure. At each step, the agent selects one of four actions-Answer, Image Retrieval, Text Retrieval, and Caption-based on its current information state. We further design an automated pipeline to collect multi-step trajectories that record the agent’s reasoning process, tool usage, and intermediate decisions. These trajectories are then used as supervision for fine-tuning. Experiments on InfoSeek and E-VQA demonstrate that our method achieves state-of-the-art performance, consistently outperforming prior baselines and confirming the effectiveness of our framework.
Anthology ID:
2026.findings-emnlp.1761
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:
37658–37684
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URL:
https://aclanthology.org/2026.findings-emnlp.1761/
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Cite (ACL):
Zhuohong Chen, ZhengXian Wu, Yunyao Yu, Hangrui Xu, Zirui Liao, Zhifang Liu, Xiangwen Deng, Peng Jiao, and Haoqian Wang. 2026. Learning to Search: A Decision-Based Agent for Knowledge-Based Visual Question Answering. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 37658–37684, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Learning to Search: A Decision-Based Agent for Knowledge-Based Visual Question Answering (Chen et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.1761.pdf