Can We Still Trace L1 Signals? Investigating the Resilience of Native Language Signals in the LLM Era

Nabelanita Utami, Ryohei Sasano


Abstract
The evolution of writing assistance tools from machine translation to large language models (LLMs) has changed how researchers write. Before the rise of LLM-based tools, non-native authors often rely more on word look-ups and individual sentence translations. Due to native language (L1) interference of the authors, the resulting work, although high in fluency, are often to have a certain "characteristics". Some examples include phrases, idioms, or certain grammar points from the author’s native language. With recent advancements, LLM-based tools can translate, proofread grammar, and even paraphrase process to make them more fluent-sounding. This is extremely helpful for authors, but it raises an interesting question: does the rise of LLM assistance in writings by non-native authors erase L1 characteristics? This study investigates this occurrence by analyzing native language identification (NLI) trends in papers, specifically abstracts, across three eras: pre-neural network (NN), pre-LLM, and post-LLM. We found consistent decline in NLI performance over time. Interestingly, the post-LLM era reveals anomalies, specifically Chinese and French show unexpected resistance or divergent trends. Additionally, we performed an experiment by using recent LLM models to paraphrase abstracts and then feed the rewritten texts into our classifiers to confirm LLM effect on writing styles. The result show that LLM use in papers reduce significantly, and the decline of NLI performance in this rewritten experiment is consistent with the NLI performance trends across periods.
Anthology ID:
2026.emnlp-main.2042
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
46549–46567
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2042/
DOI:
Bibkey:
Cite (ACL):
Nabelanita Utami and Ryohei Sasano. 2026. Can We Still Trace L1 Signals? Investigating the Resilience of Native Language Signals in the LLM Era. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 46549–46567, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Can We Still Trace L1 Signals? Investigating the Resilience of Native Language Signals in the LLM Era (Utami & Sasano, EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.2042.pdf