Forgetting in Language Models: Capacity, Optimization, and Self-Generated Replay

Fuente: arXiv
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Main Authors: Marek, Martin, Cho, Dongkyu, Qiu, Shikai, Chunara, Rumi, Izmailov, Pavel, Wilson, Andrew Gordon
Format: Preprint
Published: 2026
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author Marek, Martin
Cho, Dongkyu
Qiu, Shikai
Chunara, Rumi
Izmailov, Pavel
Wilson, Andrew Gordon
author_facet Marek, Martin
Cho, Dongkyu
Qiu, Shikai
Chunara, Rumi
Izmailov, Pavel
Wilson, Andrew Gordon
contents Models trained on a new task typically degrade on prior tasks, a phenomenon known as forgetting. Traditionally, mitigating forgetting has required replaying stored exemplars from prior tasks, which is often impractical. By contrast, language models can sample from their own training distribution, and we show that these self-generated samples serve as effective replay data, nearly eliminating forgetting. We find that forgetting nonetheless persists when the model has little remaining capacity: models pretrained close to saturation cannot absorb new information without overwriting prior knowledge. When capacity is not the limiting factor, low learning rates reduce forgetting but require substantially more training steps. Replay breaks this tradeoff, enabling fast, high-learning-rate finetuning without forgetting.
format Preprint
id arxiv_https___arxiv_org_abs_2605_26097
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Forgetting in Language Models: Capacity, Optimization, and Self-Generated Replay
Marek, Martin
Cho, Dongkyu
Qiu, Shikai
Chunara, Rumi
Izmailov, Pavel
Wilson, Andrew Gordon
Machine Learning
Models trained on a new task typically degrade on prior tasks, a phenomenon known as forgetting. Traditionally, mitigating forgetting has required replaying stored exemplars from prior tasks, which is often impractical. By contrast, language models can sample from their own training distribution, and we show that these self-generated samples serve as effective replay data, nearly eliminating forgetting. We find that forgetting nonetheless persists when the model has little remaining capacity: models pretrained close to saturation cannot absorb new information without overwriting prior knowledge. When capacity is not the limiting factor, low learning rates reduce forgetting but require substantially more training steps. Replay breaks this tradeoff, enabling fast, high-learning-rate finetuning without forgetting.
title Forgetting in Language Models: Capacity, Optimization, and Self-Generated Replay
topic Machine Learning
url https://arxiv.org/abs/2605.26097