When More Words Say Less: Decoupling Length and Specificity in Image Description Evaluation

Rhea Kapur, Robert D. Hawkins, Elisa Kreiss


Abstract
Vision-language models (VLMs) are increasingly used to make visual content accessible via text-based descriptions. In current systems, however, description specificity is often conflated with their length. We argue that these two concepts must be disentangled: descriptions can be concise yet dense with information, or lengthy yet vacuous. We define specificity relative to a contrast set, where a description is more specific to the extent that it picks out the target image better than other possible images. We construct a dataset that controls for length while varying information content, and validate that people reliably prefer more specific descriptions regardless of length. We find that controlling for length alone cannot account for differences in specificity; it matters how the length budget is applied. These results support evaluation approaches that directly prioritize specificity over verbosity.
Anthology ID:
2026.acl-short.34
Volume:
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)
Month:
July
Year:
2026
Address:
San Diego, California, United States
Editors:
Maria Liakata, Viviane P. Moreira, Jiajun Zhang, David Jurgens
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
410–422
Language:
URL:
https://preview.aclanthology.org/ingest-acl/2026.acl-short.34/
DOI:
Bibkey:
Cite (ACL):
Rhea Kapur, Robert D. Hawkins, and Elisa Kreiss. 2026. When More Words Say Less: Decoupling Length and Specificity in Image Description Evaluation. In Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers), pages 410–422, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
When More Words Say Less: Decoupling Length and Specificity in Image Description Evaluation (Kapur et al., ACL 2026)
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https://preview.aclanthology.org/ingest-acl/2026.acl-short.34.pdf
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