Rethinking LLM Unlearning Objectives: A Gradient Perspective and Go Beyond
This work addresses the need for safe and legal LLM updates by providing a unified framework to understand and enhance unlearning methods, though it is incremental as it builds on prior objectives.
The paper tackles the problem of unlearning undesirable knowledge in large language models (LLMs) by proposing a gradient-based toolkit called G-effect to analyze and improve existing unlearning objectives, leading to new insights and solutions for mitigating drawbacks.
Large language models (LLMs) should undergo rigorous audits to identify potential risks, such as copyright and privacy infringements. Once these risks emerge, timely updates are crucial to remove undesirable responses, ensuring legal and safe model usage. It has spurred recent research into LLM unlearning, focusing on erasing targeted undesirable knowledge without compromising the integrity of other, non-targeted responses. Existing studies have introduced various unlearning objectives to pursue LLM unlearning without necessitating complete retraining. However, each of these objectives has unique properties, and no unified framework is currently available to comprehend them thoroughly. To fill the gap, we propose a toolkit of the gradient effect (G-effect), quantifying the impacts of unlearning objectives on model performance from a gradient perspective. A notable advantage is its broad ability to detail the unlearning impacts from various aspects across instances, updating steps, and LLM layers. Accordingly, the G-effect offers new insights into identifying drawbacks of existing unlearning objectives, further motivating us to explore a series of new solutions for their mitigation and improvements. Finally, we outline promising directions that merit further studies, aiming at contributing to the community to advance this important field.