It’s Easier to Translate out of English than into it: Measuring Neural Translation Difficulty by Cross-Mutual Information

Emanuele Bugliarello, Sabrina J. Mielke, Antonios Anastasopoulos, Ryan Cotterell, Naoaki Okazaki


Abstract
The performance of neural machine translation systems is commonly evaluated in terms of BLEU. However, due to its reliance on target language properties and generation, the BLEU metric does not allow an assessment of which translation directions are more difficult to model. In this paper, we propose cross-mutual information (XMI): an asymmetric information-theoretic metric of machine translation difficulty that exploits the probabilistic nature of most neural machine translation models. XMI allows us to better evaluate the difficulty of translating text into the target language while controlling for the difficulty of the target-side generation component independent of the translation task. We then present the first systematic and controlled study of cross-lingual translation difficulties using modern neural translation systems. Code for replicating our experiments is available online at https://github.com/e-bug/nmt-difficulty.
Anthology ID:
2020.acl-main.149
Volume:
Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics
Month:
July
Year:
2020
Address:
Online
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1640–1649
Language:
URL:
https://aclanthology.org/2020.acl-main.149
DOI:
10.18653/v1/2020.acl-main.149
Bibkey:
Cite (ACL):
Emanuele Bugliarello, Sabrina J. Mielke, Antonios Anastasopoulos, Ryan Cotterell, and Naoaki Okazaki. 2020. It’s Easier to Translate out of English than into it: Measuring Neural Translation Difficulty by Cross-Mutual Information. In Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics, pages 1640–1649, Online. Association for Computational Linguistics.
Cite (Informal):
It’s Easier to Translate out of English than into it: Measuring Neural Translation Difficulty by Cross-Mutual Information (Bugliarello et al., ACL 2020)
Copy Citation:
PDF:
https://preview.aclanthology.org/auto-file-uploads/2020.acl-main.149.pdf
Video:
 http://slideslive.com/38929401
Code
 e-bug/nmt-difficulty