TempCore: Are Video QA Benchmarks Temporally Grounded?

Hyunjong Ok, Jaeho Lee


Abstract
Vision-language models (VLMs) can ingest only a limited number of video frames, making frame selection a practical necessity. But do current Video QA benchmarks genuinely require temporal frame selection, or can most questions be answered regardless of which frames are shown? We introduce Frame Selection Sensitivity (FSS), a per-sample diagnostic that measures how much VLM accuracy changes when the most relevant frames are replaced with the least relevant ones. Across six benchmarks and eight VLMs, we find that a large majority of samples are frame-agnostic: only a minority are genuinely sensitive to frame choice. Combining FSS with a Language Independence Score (LIS) reveals that merely 5.5--31% of samples are Temporally Sensitive. We construct TempCore, compact evaluation subsets that isolate these temporal samples from existing benchmarks, and will release code and per-sample annotations upon publication.
Anthology ID:
2026.emnlp-main.125
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
2880–2901
Language:
URL:
https://aclanthology.org/2026.emnlp-main.125/
DOI:
Bibkey:
Cite (ACL):
Hyunjong Ok and Jaeho Lee. 2026. TempCore: Are Video QA Benchmarks Temporally Grounded?. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 2880–2901, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
TempCore: Are Video QA Benchmarks Temporally Grounded? (Ok & Lee, EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.125.pdf