How Sampling Affects the Detectability of Machine-written texts: A Comprehensive Study

Matthieu Dubois, François Yvon, Pablo Piantanida


Abstract
As texts generated by Large Language Models (LLMs) are ever more common and often indistinguishable from human-written content, research on automatic text detection has attracted growing attention. Many recent detectors report near-perfect accuracy, often boasting AUROC scores above 99%. However, these claims typically assume fixed generation settings, leaving open the question of how robust such systems are to changes in decoding strategies. In this work, we systematically examine how sampling-based decoding impacts detectability, with a focus on how subtle variations in a model’s (sub)word-level distribution affect detection performance. We find that even minor adjustments to decoding parameters - such as temperature, top-p, or nucleus sampling - can severely impair detector accuracy, with AUROC dropping from near-perfect levels to 1% in some settings. Our findings expose critical blind spots in current detection methods and emphasize the need for more comprehensive evaluation protocols. To facilitate future research, we release a large-scale dataset encompassing 37 decoding configurations, along with our code and evaluation framework https://github.com/BaggerOfWords/Sampling-and-Detection.
Anthology ID:
2025.findings-emnlp.609
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2025
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
11369–11387
Language:
URL:
https://preview.aclanthology.org/author-page-yu-wang-polytechnic/2025.findings-emnlp.609/
DOI:
10.18653/v1/2025.findings-emnlp.609
Bibkey:
Cite (ACL):
Matthieu Dubois, François Yvon, and Pablo Piantanida. 2025. How Sampling Affects the Detectability of Machine-written texts: A Comprehensive Study. In Findings of the Association for Computational Linguistics: EMNLP 2025, pages 11369–11387, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
How Sampling Affects the Detectability of Machine-written texts: A Comprehensive Study (Dubois et al., Findings 2025)
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PDF:
https://preview.aclanthology.org/author-page-yu-wang-polytechnic/2025.findings-emnlp.609.pdf
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