Understanding the capability bottlenecks of embodied multimodal large language models (MLLMs) is crucial for improving embodied agents. However, existing embodied benchmarks mainly focus on task-level evaluation and fail to provide actionable insights into the underlying causes of model failures. To address this limitation, we introduce BEAR, a benchmark that decomposes embodied tasks into 14 atomic skills for fine-grained skill-level evaluation. BEAR comprises 4,469 interleaved image-video-text samples spanning 14 skills across 6 categories, ranging from low-level perception to high-level planning. We evaluate 20 MLLMs on BEAR under a hierarchical skill-level diagnosis framework and uncover two key findings: (1) perceptual capabilities are major bottlenecks behind reasoning failures, and (2) current models suffer from unstable spatiotemporal modeling that remains largely unexposed in prior benchmarks. Motivated by these findings, we further propose BEAR-Agent, a multimodal conversational agent that augments MLLMs with visual and spatial reasoning tools. BEAR-Agent substantially improves performance across embodied skills, achieving a relative improvement of 17.5% on GPT-5 over the base model on BEAR, while also outperforming strong baselines in both simulation and real-world robotic experiments. Project page: https://bear-official66.github.io/
@article{arxiv.2510.08759,
title = {Dissecting Embodied Abilities in Multimodal Language Models through Skill-level Evaluation and Diagnosis},
author = {Yu Qi and Haibo Zhao and Ziyu Guo and Siyuan Ma and Ziyan Chen and Yaokun Han and Renrui Zhang and Zitiantao Lin and Yizhe Zhu and Shiji Xin and Yijian Huang and Boce Hu and Kai Cheng and Peiheng Wang and Jiazheng Liu and Jiayi Zhang and Yizhe Zhu and Wenqing Wang and Yiran Qin and Haojie Huang and Lawson L. S. Wong},
journal= {arXiv preprint arXiv:2510.08759},
year = {2026}
}