Cited by 343Topic ModelingNatural Language Processing TechniquesMachine Learning and Data Classification

Deduplicating Training Data Makes Language Models Better

Open access
Lee, Katherine, Ippolito, Daphne, Nystrom, Andrew, Zhang, Chiyuan, Eck, Douglas, Callison-Burch, Chris, Carlini, Nicholas·2022·Proceedings of the 60th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)

Abstract

Katherine Lee, Daphne Ippolito, Andrew Nystrom, Chiyuan Zhang, Douglas Eck, Chris Callison-Burch, Nicholas Carlini. Proceedings of the 60th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers). 2022.

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Crossref · 10.18653/v1/2022.acl-long.577

Cites

51 of 51 references verified0 citation errors · 0 not checkable

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  • Deduplication improves performance on downstream tasks and decreases memorization of training data.

    “Data deduplication has become a key tool for language model projects following research showing that it both improves performance on downstream tasks (Lee et al., 2022; Zhang et al., 2021) and decreases memorization of training data (Kandpal et al., 2022).”

    From The BigScience ROOTS Corpus: A 1.6TB Composite Multilingual Dataset (2023) · cites this paper as Lee et al., 2022

    The Introduction and Conclusion report that deduplication sometimes improves language-model perplexity and helps models reach accuracy targets faster. But the paper’s “Contamination of downstream tasks” section explicitly says it does not study effects on downstream benchmark tasks, so Lee et al. do not establish that part of the citing sentence. The memorization claim is attached to Kandpal et al., not Lee et al. (LLM, conf=0.88)

    Experimental — accuracy not yet measured
  • Documents are deduplicated by title and predefined training and validation splits are used to ensure reliable evaluation.

    “To ensure reliable evaluation and improve performance [26], we deduplicate documents by title and utilize the predefined training and validation splits.”

    From Lightweight and Direct Document Relevance Optimization for Generative Information Retrieval (2025) · cites this paper as [26]

    The Introduction and §5.3 explain that deduplication can improve model performance and prevent train–validation overlap from inflating evaluation metrics. The paper describes deduplication by substring matching and document similarity, not by title; §5 discusses retaining validation or test copies when duplicates cross splits, but does not establish the claimed use of predefined splits. (LLM, conf=0.85)

    Experimental — accuracy not yet measured
  • The probability of reproducing training data correlates with its frequency of appearance, and information repeated multiple times during pretraining is more likely to be memorized and reproduced verbatim.

    “For example, the probability of reproducing training data has been shown to correlate with its frequency of appearance [12].”
  • Deduplication is a powerful strategy for improving dataset quality.

    “Deduplication is a powerful strategy for improving dataset quality (Li et al., 2024; Lee et al., 2022; Penedo et al., 2024b; Fang et al., 2025; Liu et al., 2024).”

    From OpenThoughts: Data Recipes for Reasoning Models (2025) · cites this paper as Lee et al., 2022

  • Preference-based feedback is provided only on the complete text generated by the model (trajectory) and not on specific parts of the text (particular state).

    “Moreover, it is provided only on the complete text generated by the model (trajectory) and not on specific parts of the text (particular state) [92,138].”

    From RLHF Deciphered: A Critical Analysis of Reinforcement Learning from Human Feedback for LLMs (2026) · cites this paper as [92]

    Section 6.2, “Generated Text” (page unavailable), examines whether generated text reproduces training data; it does not discuss preference-based feedback. Searches for feedback on complete trajectories versus particular states found no passage addressing that distinction. (LLM, conf=0.76)

    Experimental — accuracy not yet measured

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Cites

Flagged first, then by citations

Research works printed but not linked: 7

  1. PMLR.
  2. David Graff, Junbo Kong, Ke Chen, and Kazuaki Maeda. 2003. English gigaword. Linguistic Data Consortium, Philadelphia, 4(1):34.
  3. Paul Jaccard. 1912. The distribution of the flora in the alpine zone. New phytologist, 11(2):37-50. 10 8433
  4. Alec Radford, Jeffrey Wu, Rewon Child, David Luan, Dario Amodei, and Ilya Sutskever. 2019. Language models are unsupervised multitask learners. OpenAI blog, 1(8):9.
  5. Colin Raffel, Noam Shazeer, Adam Roberts, Kather- ine Lee, Sharan Narang, Michael Matena, Yanqi Zhou, Wei Li, and Peter J. Liu. 2020. Exploring the limits of transfer learning with a unified text-to- text transformer. Journal of Machine Learning Re- search, 21(140):1-67.
  6. PMLR.
  7. Yannick Versley and Yana Panchenko. 2012. Not just bigger: Towards better-quality web corpora. In Pro- ceedings of the seventh Web as Corpus Workshop (WAC7), pages 44-52.

Cited by

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Authors
Lee, K., Ippolito, D., Nystrom, A., Zhang, C., Eck, D., Callison-Burch, C., & Carlini, N.
Affiliations
  • Google (United States) (US)
  • University of Pennsylvania (US)
Corresponding author
Ippolito, Daphne
Venue
Proceedings of the 60th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Published
2022
Pages
8424-8445
ISSN
0736-587X (ISSN-L)
OpenAlex
W3177765786
Cited by
304
References
50
Citations by year
2026: 62 · 2025: 79 · 2024: 65 · 2023: 64 · 2022: 27 · 2021: 7
FWCI
32.49
Type
conference paper
Language
en
Open access
Licence
cc-by
Locations
Proceedings of the conference - Association for Computational Linguistics. Meeting (publishedVersion, cc-by)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Topic Modeling
  • Physical Sciences › Computer Science › Artificial Intelligence › Natural Language Processing Techniques
  • Physical Sciences › Computer Science › Artificial Intelligence › Machine Learning and Data Classification
Keywords
language model training, training data quality, duplicate removal

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