VLRewardBench: A Challenging Benchmark for Vision-Language Generative
  Reward Models
Authors: name: Lei Li, name: Yuancheng Wei, name: Zhihui Xie, name: Xuqing Yang, name: Yifan Song, name: Peiyi Wang, name: Chenxin An, name: Tianyu Liu, name: Sujian Li, name: Bill Yuchen Lin, name: Lingpeng Kong, name: Qi Liu

Vision-language generative reward models (VL-GenRMs) play a crucial role in
aligning and evaluating multimodal AI systems, yet their own evaluation remains
under-explored. Current assessment methods primarily rely on AI-annotated
preference labels from traditional VL tasks, which can introduce biases and
often fail to effectively challenge state-of-the-art models. To address these
limitations, we introduce VL-RewardBench, a comprehensive benchmark spanning
general multimodal queries, visual hallucination detection, and complex
reasoning tasks. Through our AI-assisted annotation pipeline combining sample
selection with human verification, we curate 1,250 high-quality examples
specifically designed to probe model limitations. Comprehensive evaluation
across 16 leading large vision-language models, demonstrates VL-RewardBench's
effectiveness as a challenging testbed, where even GPT-4o achieves only 65.4%
accuracy, and state-of-the-art open-source models such as Qwen2-VL-72B,
struggle to surpass random-guessing. Importantly, performance on VL-RewardBench
strongly correlates (Pearson's r > 0.9) with MMMU-Pro accuracy using Best-of-N
sampling with VL-GenRMs. Analysis experiments uncover three critical insights
for improving VL-GenRMs: (i) models predominantly fail at basic visual
perception tasks rather than reasoning tasks; (ii) inference-time scaling
benefits vary dramatically by model capacity; and (iii) training VL-GenRMs to
learn to judge substantially boosts judgment capability (+14.7% accuracy for a
7B VL-GenRM). We believe VL-RewardBench along with the experimental insights
will become a valuable resource for advancing VL-GenRMs.