如何精准删除语言模型中的特定内容?关键在选对要遗忘的数据集。
What to Forget in Unlearning? Forget Set Curation for Language Models

- 提出从海量文本中自动定位需遗忘内容的筛选方法
- 发现直接匹配关键词效果差,需考虑上下文语义与模型行为
- 适合关注模型可控性与数据安全的研究者
机器去学习旨在移除训练好的模型中特定数据或行为,而无需从头训练。然而多数评估假设待遗忘的样本已知。在真实语言模型部署中,请求方可能要求模型停止生成某首歌或某本书的内容,却不知道具体哪些片段、文档、引文或近似重复内容支撑了该行为。本文研究这一上游难题——遗忘集合筛选:将抑制请求映射到传给去学习算法的数据。提出CleanSlate基准,用于歌曲和书籍的原文输出抑制,包含模型特异性提取特征、基于内容的问答评估及能力保留测试。结果显示,自然词法和精确子串筛选器常导致抑制效果弱;而评估感知的筛选器虽能几乎完全抑制请求内容,却引发非请求内容的意外退化及模型依赖的能力损失。表明实际去学习不仅是给定遗忘集后的优化问题,所选遗忘数据本身决定了可去学习的程度以及伴随的损害。
原文摘要 · Abstract (English)
Machine unlearning aims to remove targeted data or behaviors from a trained model without retraining from scratch. Yet most evaluations assume that the examples to forget are already known. In realistic language-model deployments, a requester may ask a model to stop reproducing a song or book without knowing which spans, documents, quotations, or near-duplicates in a trillion-token corpus support that behavior. We study this missing upstream problem, forget set curation: mapping a suppression request to the data passed to an unlearning algorithm. We introduce CleanSlate, a benchmark for verbatim output suppression over songs and books, with model-specific extraction profiles, content-grounded QA, and capability-retention evaluations. CleanSlate exposes two failure modes. Natural lexical and exact-substring curators often yield forget sets that lead to weak suppression. An evaluation-aware curator suppresses requested continuations almost completely, but causes collateral regression on non-requested content and model-dependent capability loss. These results show that practical unlearning is not only an optimization problem once a forget set is given: the data chosen for forgetting determines both what can be unlearnt and what else is damaged.
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