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Hauptverfasser: Zhang, Qingjie, Wang, Di, Qian, Haoting, Yan, Liu, Zhang, Tianwei, Xu, Ke, Li, Qi, Huang, Minlie, Li, Hewu, Qiu, Han
Format: Preprint
Veröffentlicht: 2025
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Online-Zugang:https://arxiv.org/abs/2508.17771
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author Zhang, Qingjie
Wang, Di
Qian, Haoting
Yan, Liu
Zhang, Tianwei
Xu, Ke
Li, Qi
Huang, Minlie
Li, Hewu
Qiu, Han
author_facet Zhang, Qingjie
Wang, Di
Qian, Haoting
Yan, Liu
Zhang, Tianwei
Xu, Ke
Li, Qi
Huang, Minlie
Li, Hewu
Qiu, Han
contents Tokens are basic elements in the datasets for LLM training. It is well-known that many tokens representing Chinese phrases in the vocabulary of GPT (4o/4o-mini/o1/o3/4.5/4.1/o4-mini) are indicating contents like pornography or online gambling. Based on this observation, our goal is to locate Polluted Chinese (PoC) tokens in LLMs and study the relationship between PoC tokens' existence and training data. (1) We give a formal definition and taxonomy of PoC tokens based on the GPT's vocabulary. (2) We build a PoC token detector via fine-tuning an LLM to label PoC tokens in vocabularies by considering each token's both semantics and related contents from the search engines. (3) We study the speculation on the training data pollution via PoC tokens' appearances (token ID). Experiments on GPT and other 23 LLMs indicate that tokens widely exist while GPT's vocabulary behaves the worst: more than 23% long Chinese tokens (i.e., a token with more than two Chinese characters) are either porn or online gambling. We validate the accuracy of our speculation method on famous pre-training datasets like C4 and Pile. Then, considering GPT-4o, we speculate that the ratio of "Yui Hatano" related webpages in GPT-4o's training data is around 0.5%.
format Preprint
id arxiv_https___arxiv_org_abs_2508_17771
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Speculating LLMs' Chinese Training Data Pollution from Their Tokens
Zhang, Qingjie
Wang, Di
Qian, Haoting
Yan, Liu
Zhang, Tianwei
Xu, Ke
Li, Qi
Huang, Minlie
Li, Hewu
Qiu, Han
Computation and Language
Tokens are basic elements in the datasets for LLM training. It is well-known that many tokens representing Chinese phrases in the vocabulary of GPT (4o/4o-mini/o1/o3/4.5/4.1/o4-mini) are indicating contents like pornography or online gambling. Based on this observation, our goal is to locate Polluted Chinese (PoC) tokens in LLMs and study the relationship between PoC tokens' existence and training data. (1) We give a formal definition and taxonomy of PoC tokens based on the GPT's vocabulary. (2) We build a PoC token detector via fine-tuning an LLM to label PoC tokens in vocabularies by considering each token's both semantics and related contents from the search engines. (3) We study the speculation on the training data pollution via PoC tokens' appearances (token ID). Experiments on GPT and other 23 LLMs indicate that tokens widely exist while GPT's vocabulary behaves the worst: more than 23% long Chinese tokens (i.e., a token with more than two Chinese characters) are either porn or online gambling. We validate the accuracy of our speculation method on famous pre-training datasets like C4 and Pile. Then, considering GPT-4o, we speculate that the ratio of "Yui Hatano" related webpages in GPT-4o's training data is around 0.5%.
title Speculating LLMs' Chinese Training Data Pollution from Their Tokens
topic Computation and Language
url https://arxiv.org/abs/2508.17771