Token Prediction as Implicit Classification to Identify LLM-Generated Text

Yutian Chen, Hao Kang, Vivian Zhai, Liangze Li, Rita Singh, Bhiksha Raj


Abstract
This paper introduces a novel approach for identifying the possible large language models (LLMs) involved in text generation. Instead of adding an additional classification layer to a base LM, we reframe the classification task as a next-token prediction task and directly fine-tune the base LM to perform it. We utilize the Text-to-Text Transfer Transformer (T5) model as the backbone for our experiments. We compared our approach to the more direct approach of utilizing hidden states for classification. Evaluation shows the exceptional performance of our method in the text classification task, highlighting its simplicity and efficiency. Furthermore, interpretability studies on the features extracted by our model reveal its ability to differentiate distinctive writing styles among various LLMs even in the absence of an explicit classifier. We also collected a dataset named OpenLLMText, containing approximately 340k text samples from human and LLMs, including GPT3.5, PaLM, LLaMA, and GPT2.
Anthology ID:
2023.emnlp-main.810
Volume:
Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processing
Month:
December
Year:
2023
Address:
Singapore
Editors:
Houda Bouamor, Juan Pino, Kalika Bali
Venue:
EMNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
13112–13120
Language:
URL:
https://aclanthology.org/2023.emnlp-main.810
DOI:
10.18653/v1/2023.emnlp-main.810
Bibkey:
Cite (ACL):
Yutian Chen, Hao Kang, Vivian Zhai, Liangze Li, Rita Singh, and Bhiksha Raj. 2023. Token Prediction as Implicit Classification to Identify LLM-Generated Text. In Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processing, pages 13112–13120, Singapore. Association for Computational Linguistics.
Cite (Informal):
Token Prediction as Implicit Classification to Identify LLM-Generated Text (Chen et al., EMNLP 2023)
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PDF:
https://aclanthology.org/2023.emnlp-main.810.pdf
Video:
 https://aclanthology.org/2023.emnlp-main.810.mp4