Evaluating Cross-Modal Reasoning Ability and Problem Characteristics with Multimodal Item Response Theory - Uebayashi, Shunki; Masui, Kento; Atarashi, Kyohei; Bao, Han; Kashima, Hisashi; Inoue, Naoto; Otani, Mayu; Takeuchi, Koh (International Conference on Learning Representations, 2026)