A Neuro-inspired Interpretation of Unlearning in Large Language Models through Sample-level Unlearning Difficulty

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Hauptverfasser: Feng, Xiaohua, Li, Yuyuan, Wang, Chengye, Liu, Junlin, Zhang, Li, Chen, Chaochao
Format: Preprint
Veröffentlicht: 2025
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author Feng, Xiaohua
Li, Yuyuan
Wang, Chengye
Liu, Junlin
Zhang, Li
Chen, Chaochao
author_facet Feng, Xiaohua
Li, Yuyuan
Wang, Chengye
Liu, Junlin
Zhang, Li
Chen, Chaochao
contents Driven by privacy protection laws and regulations, unlearning in Large Language Models (LLMs) is gaining increasing attention. However, current research often neglects the interpretability of the unlearning process, particularly concerning sample-level unlearning difficulty. Existing studies typically assume a uniform unlearning difficulty across samples. This simplification risks attributing the performance of unlearning algorithms to sample selection rather than the algorithm's design, potentially steering the development of LLM unlearning in the wrong direction. Thus, we investigate the relationship between LLM unlearning and sample characteristics, with a focus on unlearning difficulty. Drawing inspiration from neuroscience, we propose a Memory Removal Difficulty ($\mathrm{MRD}$) metric to quantify sample-level unlearning difficulty. Using $\mathrm{MRD}$, we analyze the characteristics of hard-to-unlearn versus easy-to-unlearn samples. Furthermore, we propose an $\mathrm{MRD}$-based weighted sampling method to optimize existing unlearning algorithms, which prioritizes easily forgettable samples, thereby improving unlearning efficiency and effectiveness. We validate the proposed metric and method using public benchmarks and datasets, with results confirming its effectiveness.
format Preprint
id arxiv_https___arxiv_org_abs_2504_06658
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Neuro-inspired Interpretation of Unlearning in Large Language Models through Sample-level Unlearning Difficulty
Feng, Xiaohua
Li, Yuyuan
Wang, Chengye
Liu, Junlin
Zhang, Li
Chen, Chaochao
Machine Learning
Artificial Intelligence
Computation and Language
Driven by privacy protection laws and regulations, unlearning in Large Language Models (LLMs) is gaining increasing attention. However, current research often neglects the interpretability of the unlearning process, particularly concerning sample-level unlearning difficulty. Existing studies typically assume a uniform unlearning difficulty across samples. This simplification risks attributing the performance of unlearning algorithms to sample selection rather than the algorithm's design, potentially steering the development of LLM unlearning in the wrong direction. Thus, we investigate the relationship between LLM unlearning and sample characteristics, with a focus on unlearning difficulty. Drawing inspiration from neuroscience, we propose a Memory Removal Difficulty ($\mathrm{MRD}$) metric to quantify sample-level unlearning difficulty. Using $\mathrm{MRD}$, we analyze the characteristics of hard-to-unlearn versus easy-to-unlearn samples. Furthermore, we propose an $\mathrm{MRD}$-based weighted sampling method to optimize existing unlearning algorithms, which prioritizes easily forgettable samples, thereby improving unlearning efficiency and effectiveness. We validate the proposed metric and method using public benchmarks and datasets, with results confirming its effectiveness.
title A Neuro-inspired Interpretation of Unlearning in Large Language Models through Sample-level Unlearning Difficulty
topic Machine Learning
Artificial Intelligence
Computation and Language
url https://arxiv.org/abs/2504.06658