Issues with Entailment-based Zero-shot Text Classification

Tingting Ma, Jin-Ge Yao, Chin-Yew Lin, Tiejun Zhao


Abstract
The general format of natural language inference (NLI) makes it tempting to be used for zero-shot text classification by casting any target label into a sentence of hypothesis and verifying whether or not it could be entailed by the input, aiming at generic classification applicable on any specified label space. In this opinion piece, we point out a few overlooked issues that are yet to be discussed in this line of work. We observe huge variance across different classification datasets amongst standard BERT-based NLI models and surprisingly find that pre-trained BERT without any fine-tuning can yield competitive performance against BERT fine-tuned for NLI. With the concern that these models heavily rely on spurious lexical patterns for prediction, we also experiment with preliminary approaches for more robust NLI, but the results are in general negative. Our observations reveal implicit but challenging difficulties in entailment-based zero-shot text classification.
Anthology ID:
2021.acl-short.99
Volume:
Proceedings of the 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing (Volume 2: Short Papers)
Month:
August
Year:
2021
Address:
Online
Editors:
Chengqing Zong, Fei Xia, Wenjie Li, Roberto Navigli
Venues:
ACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
786–796
Language:
URL:
https://aclanthology.org/2021.acl-short.99
DOI:
10.18653/v1/2021.acl-short.99
Bibkey:
Cite (ACL):
Tingting Ma, Jin-Ge Yao, Chin-Yew Lin, and Tiejun Zhao. 2021. Issues with Entailment-based Zero-shot Text Classification. In Proceedings of the 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing (Volume 2: Short Papers), pages 786–796, Online. Association for Computational Linguistics.
Cite (Informal):
Issues with Entailment-based Zero-shot Text Classification (Ma et al., ACL-IJCNLP 2021)
Copy Citation:
PDF:
https://aclanthology.org/2021.acl-short.99.pdf
Optional supplementary material:
 2021.acl-short.99.OptionalSupplementaryMaterial.zip
Video:
 https://aclanthology.org/2021.acl-short.99.mp4
Code
 mtt1998/issues-nli
Data
AG NewsFEVERGLUEMultiNLISNIPSSSTSST-2