Probing for the Usage of Grammatical Number

Karim Lasri, Tiago Pimentel, Alessandro Lenci, Thierry Poibeau, Ryan Cotterell


Abstract
A central quest of probing is to uncover how pre-trained models encode a linguistic property within their representations. An encoding, however, might be spurious—i.e., the model might not rely on it when making predictions. In this paper, we try to find an encoding that the model actually uses, introducing a usage-based probing setup. We first choose a behavioral task which cannot be solved without using the linguistic property. Then, we attempt to remove the property by intervening on the model’s representations. We contend that, if an encoding is used by the model, its removal should harm the performance on the chosen behavioral task. As a case study, we focus on how BERT encodes grammatical number, and on how it uses this encoding to solve the number agreement task. Experimentally, we find that BERT relies on a linear encoding of grammatical number to produce the correct behavioral output. We also find that BERT uses a separate encoding of grammatical number for nouns and verbs. Finally, we identify in which layers information about grammatical number is transferred from a noun to its head verb.
Anthology ID:
2022.acl-long.603
Original:
2022.acl-long.603v1
Version 2:
2022.acl-long.603v2
Volume:
Proceedings of the 60th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
May
Year:
2022
Address:
Dublin, Ireland
Editors:
Smaranda Muresan, Preslav Nakov, Aline Villavicencio
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
8818–8831
Language:
URL:
https://aclanthology.org/2022.acl-long.603
DOI:
10.18653/v1/2022.acl-long.603
Bibkey:
Cite (ACL):
Karim Lasri, Tiago Pimentel, Alessandro Lenci, Thierry Poibeau, and Ryan Cotterell. 2022. Probing for the Usage of Grammatical Number. In Proceedings of the 60th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 8818–8831, Dublin, Ireland. Association for Computational Linguistics.
Cite (Informal):
Probing for the Usage of Grammatical Number (Lasri et al., ACL 2022)
Copy Citation:
PDF:
https://aclanthology.org/2022.acl-long.603.pdf
Video:
 https://aclanthology.org/2022.acl-long.603.mp4