Towards Top-Down Reasoning: An Explainable Multi-Agent Approach for Visual Question Answering

Recently, several methods have been proposed to augment large Vision Language Models (VLMs) for Visual Question Answering (VQA) simplicity by incorporating external knowledge from knowledge bases or visual clues derived from question decomposition. Although having achieved promising results, these methods still suffer from the challenge that VLMs cannot inherently understand the incorporated knowledge and might fail to generate the optimal answers. Contrarily, human cognition engages visual questions through a top-down reasoning process, systematically exploring relevant issues to derive a comprehensive answer. This not only facilitates an accurate answer but also provides a transparent rationale for the decision-making pathway. Motivated by this cognitive mechanism, we introduce a novel, explainable multi-agent collaboration framework designed to imitate human-like top-down reasoning by leveraging the expansive knowledge of LLMs. Our framework comprises three agents, i.e., Responder, Seeker, and Integrator, each contributing uniquely to the top-down reasoning process. The VLM-based Responder generates the answer candidates for the question and gives responses to other issues. The Seeker, primarily based on LLM, identifies relevant issues related to the question to inform the Responder and constructs a Multi-View Knowledge Base (MVKB) for the given visual scene by leveraging the understanding capabilities of LLM. The Integrator agent combines information from the Seeker and the Responder to produce the final VQA answer. Through this collaboration mechanism, our framework explicitly constructs an MVKB for a specific visual scene and reasons answers in a top-down reasoning process. Extensive and comprehensive evaluations on diverse VQA datasets and VLMs demonstrate the superior applicability and interpretability of our framework over the existing compared methods.