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LM-Critic: Language Models for Unsupervised Grammatical Error Correction

2021-09-14EMNLP 2021Code Available1· sign in to hype

Michihiro Yasunaga, Jure Leskovec, Percy Liang

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Abstract

Training a model for grammatical error correction (GEC) requires a set of labeled ungrammatical / grammatical sentence pairs, but manually annotating such pairs can be expensive. Recently, the Break-It-Fix-It (BIFI) framework has demonstrated strong results on learning to repair a broken program without any labeled examples, but this relies on a perfect critic (e.g., a compiler) that returns whether an example is valid or not, which does not exist for the GEC task. In this work, we show how to leverage a pretrained language model (LM) in defining an LM-Critic, which judges a sentence to be grammatical if the LM assigns it a higher probability than its local perturbations. We apply this LM-Critic and BIFI along with a large set of unlabeled sentences to bootstrap realistic ungrammatical / grammatical pairs for training a corrector. We evaluate our approach on GEC datasets across multiple domains (CoNLL-2014, BEA-2019, GMEG-wiki and GMEG-yahoo) and show that it outperforms existing methods in both the unsupervised setting (+7.7 F0.5) and the supervised setting (+0.5 F0.5).

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Benchmark Results

DatasetModelMetricClaimedVerifiedStatus
BEA-2019 (test)LM-CriticF0.572.9Unverified
CoNLL-2014 Shared TaskLM-CriticF0.565.8Unverified
Restricted+ BIFI with no criticF0.518.7Unverified
Unrestricted+ BIFI (ours)F0.542.4Unverified

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