Saejin Kim


2025

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Zero-shot Multimodal Document Retrieval via Cross-modal Question Generation
Yejin Choi | Jaewoo Park | Janghan Yoon | Saejin Kim | Jaehyun Jeon | Youngjae Yu
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing

Rapid advances in Multimodal Large Language Models (MLLMs) have extended information retrieval beyond text, enabling access to complex real-world documents that combine both textual and visual content. However, most documents are private, either owned by individuals or confined within corporate silos, and current retrievers struggle when faced with unseen domains or languages. To address this gap, we introduce PREMIR, a simple yet effective framework that leverages the broad knowledge of an MLLM to generate cross-modal pre-questions (preQs) before retrieval. Unlike earlier multimodal retrievers that embed entire documents as a single vector, PREMIR leverages preQs, decomposed from documents into finer token-level representations across modalities, enabling richer contextual understanding. Experiments show that PREMIR achieves state-of-the-art performance on out-of-distribution benchmarks, including closed-domain and multilingual settings, outperforming strong baselines across all metrics. We confirm the contribution of each component through in-depth ablation studies, and qualitative analyses of the generated preQs further highlight the framework’s robustness in real-world settings.

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Multimodal UNcommonsense: From Odd to Ordinary and Ordinary to Odd
Yejin Son | Saejin Kim | Dongjun Min | Youngjae Yu
Findings of the Association for Computational Linguistics: EMNLP 2025

Commonsense reasoning in multimodal contexts remains a foundational challenge in artificial intelligence. We introduce Multimodal UNcommonsense (MUN), a benchmark designed to evaluate models’ ability to handle scenarios that deviate from typical visual or contextual expectations. MUN pairs visual scenes with surprising or unlikely outcomes described in natural language, prompting models to either rationalize seemingly odd images using everyday logic or uncover unexpected interpretations in ordinary scenes. To support this task, we propose a retrieval-based in-context learning (R-ICL) framework that transfers reasoning capabilities from larger models to smaller ones without additional training. Leveraging a novel Multimodal Ensemble Retriever (MER), our method identifies semantically relevant exemplars even when image and text pairs are deliberately discordant. Experiments show an average improvement of 8.3% over baseline ICL methods, highlighting the effectiveness of R-ICL in low-frequency, atypical settings. MUN opens new directions for evaluating and improving visual-language models’ robustness and adaptability in real-world, culturally diverse, and non-prototypical scenarios.