MEOW: MEMOry Supervised LLM Unlearning Via Inverted Facts

TL;DR

This work uses an offline LLM to generate a set of inverted facts, then designs a new metric, MEMO, to quantify memorization in LLMs, and proposes MEOW, a simple yet effective gradient descent-based unlearning method.

Abstract

Large Language Models (LLMs) can memorize sensitive information, raising concerns about potential misuse. LLM Unlearning, a post-hoc approach to remove this information from trained LLMs, offers a promising solution to mitigate these risks. However, previous practices face three key challenges: 1. Utility: successful unlearning often causes catastrophic collapse on unrelated tasks. 2. Efficiency: many methods either involve adding similarly sized models, which slows down unlearning or inference, or require retain data that are difficult to obtain. 3. Robustness: even effective methods may still leak data via extraction techniques. To address these challenges, we propose MEOW, a simple yet effective gradient descent-based unlearning method. Specifically, we use an offline LLM to generate a set of inverted facts. Then, we design a new metric, MEMO, to quantify memorization in LLMs. Finally, based on the signals provided by MEMO, we select the most appropriate set of inverted facts and finetune the model based on them. We evaluate MEOW on the commonly used unlearn benchmark, ToFU, with Llama2-7B-Chat and Phi-1.5B, and test it on both NLU and NLG tasks. Results demonstrate significant improvement of MEOW in forget quality without substantial loss in model utility. Meanwhile, MEOW does not exhibit significant degradation in NLU or NLG capabilities, and there is even a slight improvement in NLU performance.

Figures (11)

• Figure 1: Overview of MEOW.
• Figure 2: MEMO with prefix or suffix mode.
• Figure 3: MEMO in different LLMs.
• Figure 4: Sensitivity of MEMO for different Rouge-N.
• Figure 5: Performance on different numbers of inverted facts and selection strategies.