Pragmatically Informative Image Captioning with Character-Level Inference

Reuben Cohn-Gordon, Noah Goodman, Christopher Potts


Abstract
We combine a neural image captioner with a Rational Speech Acts (RSA) model to make a system that is pragmatically informative: its objective is to produce captions that are not merely true but also distinguish their inputs from similar images. Previous attempts to combine RSA with neural image captioning require an inference which normalizes over the entire set of possible utterances. This poses a serious problem of efficiency, previously solved by sampling a small subset of possible utterances. We instead solve this problem by implementing a version of RSA which operates at the level of characters (“a”, “b”, “c”, ...) during the unrolling of the caption. We find that the utterance-level effect of referential captions can be obtained with only character-level decisions. Finally, we introduce an automatic method for testing the performance of pragmatic speaker models, and show that our model outperforms a non-pragmatic baseline as well as a word-level RSA captioner.
Anthology ID:
N18-2070
Volume:
Proceedings of the 2018 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, Volume 2 (Short Papers)
Month:
June
Year:
2018
Address:
New Orleans, Louisiana
Editors:
Marilyn Walker, Heng Ji, Amanda Stent
Venue:
NAACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
439–443
Language:
URL:
https://aclanthology.org/N18-2070
DOI:
10.18653/v1/N18-2070
Bibkey:
Cite (ACL):
Reuben Cohn-Gordon, Noah Goodman, and Christopher Potts. 2018. Pragmatically Informative Image Captioning with Character-Level Inference. In Proceedings of the 2018 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, Volume 2 (Short Papers), pages 439–443, New Orleans, Louisiana. Association for Computational Linguistics.
Cite (Informal):
Pragmatically Informative Image Captioning with Character-Level Inference (Cohn-Gordon et al., NAACL 2018)
Copy Citation:
PDF:
https://aclanthology.org/N18-2070.pdf
Video:
 https://aclanthology.org/N18-2070.mp4
Data
Visual Genome