Replicating and Extending “Because Their Treebanks Leak”: Graph Isomorphism, Covariants, and Parser Performance

Mark Anderson, Anders Søgaard, Carlos Gómez-Rodríguez


Abstract
Søgaard (2020) obtained results suggesting the fraction of trees occurring in the test data isomorphic to trees in the training set accounts for a non-trivial variation in parser performance. Similar to other statistical analyses in NLP, the results were based on evaluating linear regressions. However, the study had methodological issues and was undertaken using a small sample size leading to unreliable results. We present a replication study in which we also bin sentences by length and find that only a small subset of sentences vary in performance with respect to graph isomorphism. Further, the correlation observed between parser performance and graph isomorphism in the wild disappears when controlling for covariants. However, in a controlled experiment, where covariants are kept fixed, we do observe a correlation. We suggest that conclusions drawn from statistical analyses like this need to be tempered and that controlled experiments can complement them by more readily teasing factors apart.
Anthology ID:
2021.acl-short.138
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
Venues:
ACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1090–1098
Language:
URL:
https://aclanthology.org/2021.acl-short.138
DOI:
10.18653/v1/2021.acl-short.138
Bibkey:
Cite (ACL):
Mark Anderson, Anders Søgaard, and Carlos Gómez-Rodríguez. 2021. Replicating and Extending “Because Their Treebanks Leak”: Graph Isomorphism, Covariants, and Parser Performance. 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 1090–1098, Online. Association for Computational Linguistics.
Cite (Informal):
Replicating and Extending “Because Their Treebanks Leak”: Graph Isomorphism, Covariants, and Parser Performance (Anderson et al., ACL-IJCNLP 2021)
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PDF:
https://aclanthology.org/2021.acl-short.138.pdf
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 2021.acl-short.138.OptionalSupplementaryMaterial.zip
Video:
 https://aclanthology.org/2021.acl-short.138.mp4