SEAM: Semantically Equivalent Across Modalities Benchmark for
  Vision-Language Models
Authors: name: Zhenwei Tang; name: Difan Jiao; name: Blair Yang; name: Ashton Anderson
Published: 2025-08-25 16:33:07

Abstract: Evaluating whether vision-language models (VLMs) reason consistently across
representations is challenging because modality comparisons are typically
confounded by task differences and asymmetric information. We introduce SEAM, a
benchmark that pairs semantically equivalent inputs across four domains that
have existing standardized textual and visual notations. By employing distinct
notation systems across modalities, in contrast to OCR-based image-text
pairing, SEAM provides a rigorous comparative assessment of the
textual-symbolic and visual-spatial reasoning capabilities of VLMs. Across 21
contemporary models, we observe systematic modality imbalance: vision
frequently lags language in overall performance, despite the problems
containing semantically equivalent information, and cross-modal agreement is
relatively low. Our error analysis reveals two main drivers: textual perception
failures from tokenization in domain notation and visual perception failures
that induce hallucinations. We also show that our results are largely robust to
visual transformations. SEAM establishes a controlled, semantically equivalent
setting for measuring and improving modality-agnostic reasoning.