SPECI: Fine-grained Evaluation of Specificity for Image Captioning

Son T. Luu, Hiep K. V. Nguyen, Trung Bui, Viet Dac Lai, Le-Minh Nguyen


Abstract
Image Captioning lies at the center of synthetic data generation in computer vision. The quality of the caption defines the behavior of the resulting model trained on image-caption pairs generated by Image Captioning. Measuring the specificity of image captioning plays an important role in supplying high-quality captions for the downstream tasks. To address the challenge of automatically assessing the quality of the caption, we propose SPECI, an automatic metric that decomposes dense captions into atomic facts and evaluates specificity across visual criteria such as granularity, spatial detail, color, and linguistic focus using WordNet-based hyponym levels. Empirical results on the benchmark datasets demonstrate significant correlation with human judgments, and its application in image captioning and image reconstruction tasks highlights the practical utility of SPECI. The source code of SPECI is available at https://github.com/sonlam1102/SPECI.
Anthology ID:
2026.aacl-long.7
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
140–156
Language:
URL:
https://aclanthology.org/2026.aacl-long.7/
DOI:
Bibkey:
Cite (ACL):
Son T. Luu, Hiep K. V. Nguyen, Trung Bui, Viet Dac Lai, and Le-Minh Nguyen. 2026. SPECI: Fine-grained Evaluation of Specificity for Image Captioning. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 140–156, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
SPECI: Fine-grained Evaluation of Specificity for Image Captioning (Luu et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.7.pdf