Advancing Machine-Generated Text Detection from an Easy to Hard Supervision Perspective
This work addresses the challenge of inexact supervision in machine-generated text detection, which is crucial for applications like content moderation and academic integrity, though it appears incremental as it builds on existing detection paradigms.
The paper tackles the problem of boundary ambiguity in machine-generated text detection by proposing an easy-to-hard enhancement framework that uses a simpler supervisor to improve a more challenging detector, achieving significant detection effectiveness across diverse scenarios like cross-LLM and paraphrase attacks.
Existing machine-generated text (MGT) detection methods implicitly assume labels as the "golden standard". However, we reveal boundary ambiguity in MGT detection, implying that traditional training paradigms are inexact. Moreover, limitations of human cognition and the superintelligence of detectors make inexact learning widespread and inevitable. To this end, we propose an easy-to-hard enhancement framework to provide reliable supervision under such inexact conditions. Distinct from knowledge distillation, our framework employs an easy supervisor targeting relatively simple longer-text detection tasks (despite weaker capabilities), to enhance the more challenging target detector. Firstly, longer texts targeted by supervisors theoretically alleviate the impact of inexact labels, laying the foundation for reliable supervision. Secondly, by structurally incorporating the detector into the supervisor, we theoretically model the supervisor as a lower performance bound for the detector. Thus, optimizing the supervisor indirectly optimizes the detector, ultimately approximating the underlying "golden" labels. Extensive experiments across diverse practical scenarios, including cross-LLM, cross-domain, mixed text, and paraphrase attacks, demonstrate the framework's significant detection effectiveness. The code is available at: https://github.com/tmlr-group/Easy2Hard.