English

Ensembling Multiple Hallucination Detectors Trained on VLLM Internal Representations

Information Retrieval 2025-12-29 v2

Abstract

This paper presents the 5th place solution by our team, y3h2, for the Meta CRAG-MM Challenge at KDD Cup 2025. The CRAG-MM benchmark is a visual question answering (VQA) dataset focused on factual questions about images, including egocentric images. The competition was contested based on VQA accuracy, as judged by an LLM-based automatic evaluator. Since incorrect answers result in negative scores, our strategy focused on reducing hallucinations from the internal representations of the VLM. Specifically, we trained logistic regression-based hallucination detection models using both the hidden_state and the outputs of specific attention heads. We then employed an ensemble of these models. As a result, while our method sacrificed some correct answers, it significantly reduced hallucinations and allowed us to place among the top entries on the final leaderboard.

Keywords

Cite

@article{arxiv.2510.14330,
  title  = {Ensembling Multiple Hallucination Detectors Trained on VLLM Internal Representations},
  author = {Yuto Nakamizo and Ryuhei Miyazato and Hikaru Tanabe and Ryuta Yamakura and Kiori Hatanaka},
  journal= {arXiv preprint arXiv:2510.14330},
  year   = {2025}
}

Comments

5th place solution at Meta KDD Cup 2025

R2 v1 2026-07-01T06:40:31.730Z