SSMBA: Self-Supervised Manifold Based Data Augmentation for Improving Out-of-Domain Robustness
Paper · 2020 · Nathan Ng, Kyunghyun Cho and Marzyeh Ghassemi
Summary
Classifiers and sequence models trained on one domain often perform poorly on out-of-domain (OOD) inputs. For images, simple transformations like rotation keep new examples realistic, but no comparable meaning-preserving operations exist for text. The authors propose SSMBA, a task-agnostic augmentation scheme based on denoising autoencoders. It works in two steps:
- It corrupts a training input so that it leaves the data manifold, using the MLM masking procedure.
- It restores the input with a pre-trained masked language model, which pulls it back onto the manifold.
The new examples get their labels in one of two ways: they inherit the label of the source example, or a teacher model fit to the unaugmented training set assigns them. The method needs no task knowledge and no dataset-specific fine-tuning. It was tested on sentiment analysis, NLI and machine translation, covering 9 datasets and 4 model types. SSMBA beat both unaugmented baselines and competing augmentation methods, in-domain and OOD. This makes it a cheap, general tool for improving robustness, including in low-resource settings.
Key points
- Headline gains: +0.8% OOD accuracy on Amazon reviews, +1.8% OOD accuracy on MNLI, and +1.4 BLEU in-domain on IWSLT14 German-English.
- Benchmarks:
- Sentiment: AR-Full, AR-Clothing, Yelp, and Movies (SST2 paired with IMDb).
- NLI: MNLI and ANLI (R1–R3).
- Machine translation: IWSLT14 de→en, OPUS (train on medical, test on Koran, Ubuntu, subtitles and legal text), and de→rm (Allegra corpus plus Swiss press releases, tested on Convivenza blogs).
- Ablations on reconstruction and sampling:
- The choice of reconstruction model matters little: DistilRoBERTa (82M), RoBERTa BASE (125M) and RoBERTa LARGE (355M) give similar improvements.
- Unrestricted sampling from the MLM outperforms top-k sampling.
- Ablations on corruption and data size:
- For sentiment, OOD accuracy is best at about 45% corrupted tokens, and augmented models still beat the baseline even at 95%. The NLI task, by contrast, is hurt by heavy corruption.
- Generating more augmented sentences per example raises gains and lowers variance.
- Benefits persist with fewer than 100 training examples.
- Code: available at github.com/nng555/ssmba.
Institutions
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Cite
Cite as Nathan Ng, Kyunghyun Cho and Marzyeh Ghassemi. 2020. SSMBA: Self-Supervised Manifold Based Data Augmentation for Improving Out-of-Domain Robustness. Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP).
@inproceedings{ng2020ssmba,
title = {{SSMBA: Self-Supervised Manifold Based Data Augmentation for Improving Out-of-Domain Robustness}},
author = {Nathan Ng, Kyunghyun Cho and Marzyeh Ghassemi},
booktitle = {Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP)},
year = {2020},
doi = {10.18653/v1/2020.emnlp-main.97},
url = {https://doi.org/10.18653/v1/2020.emnlp-main.97}
}References
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