ResearchResearch paperLarge Language Models1 source · Oct 7, 2026

Why Forget-Only Unlearning Needs Memorization

In this work, we study forget-only unlearning, where the deletion algorithm receives only the trained model and the examples to forget, with no retained data or extra training information.

Key points

  • Machine unlearning asks for a deletion algorithm whose output is close to retraining from scratch without the selected forget examples.
  • We ask whether forget-only unlearning is always possible.
  • Using this observation, we derive lower bounds on how accurately unlearning can match retraining and instantiate them for several standard learning algorithms.
  • Overall, our results show that information discarded during ordinary learning may be needed later for deletion, so models designed for forget-only unlearning may need to retain more information than standard training does.

Sources (1)

  • [1]Why Forget-Only Unlearning Needs Memorization
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 7, 05:55 PM
    In this work, we study forget-only unlearning, where the deletion algorithm receives only the trained model and the examples to forget, with no retained data or extra training information.
    Machine unlearning asks for a deletion algorithm whose output is close to retraining from scratch without the selected forget examples.

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