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Structural Supervision Improves Learning of Non-Local Grammatical Dependencies

Ethan Wilcox, Peng Qian, Richard Futrell, Miguel Ballesteros, Roger Levy


Abstract
State-of-the-art LSTM language models trained on large corpora learn sequential contingencies in impressive detail, and have been shown to acquire a number of non-local grammatical dependencies with some success. Here we investigate whether supervision with hierarchical structure enhances learning of a range of grammatical dependencies, a question that has previously been addressed only for subject-verb agreement. Using controlled experimental methods from psycholinguistics, we compare the performance of word-based LSTM models versus Recurrent Neural Network Grammars (RNNGs) (Dyer et al. 2016) which represent hierarchical syntactic structure and use neural control to deploy it in left-to-right processing, on two classes of non-local grammatical dependencies in English—Negative Polarity licensing and Filler-Gap Dependencies—tested in a range of configurations. Using the same training data for both models, we find that the RNNG outperforms the LSTM on both types of grammatical dependencies and even learns many of the Island Constraints on the filler-gap dependency. Structural supervision thus provides data efficiency advantages over purely string-based training of neural language models in acquiring human-like generalizations about non-local grammatical dependencies.
Anthology ID:
N19-1334
Volume:
Proceedings of the 2019 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, Volume 1 (Long and Short Papers)
Month:
June
Year:
2019
Address:
Minneapolis, Minnesota
Editors:
Jill Burstein, Christy Doran, Thamar Solorio
Venue:
NAACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
3302–3312
Language:
URL:
https://aclanthology.org/N19-1334
DOI:
10.18653/v1/N19-1334
Bibkey:
Cite (ACL):
Ethan Wilcox, Peng Qian, Richard Futrell, Miguel Ballesteros, and Roger Levy. 2019. Structural Supervision Improves Learning of Non-Local Grammatical Dependencies. In Proceedings of the 2019 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, Volume 1 (Long and Short Papers), pages 3302–3312, Minneapolis, Minnesota. Association for Computational Linguistics.
Cite (Informal):
Structural Supervision Improves Learning of Non-Local Grammatical Dependencies (Wilcox et al., NAACL 2019)
Copy Citation:
PDF:
https://aclanthology.org/N19-1334.pdf
Data
Penn Treebank