An Empirical Study of Catastrophic Forgetting in Large Language Models During Continual Fine-tuning

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Main Authors: Luo, Yun, Yang, Zhen, Meng, Fandong, Li, Yafu, Zhou, Jie, Zhang, Yue
Format: Preprint
Published: 2023
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_version_ 1866913635285073920
author Luo, Yun
Yang, Zhen
Meng, Fandong
Li, Yafu
Zhou, Jie
Zhang, Yue
author_facet Luo, Yun
Yang, Zhen
Meng, Fandong
Li, Yafu
Zhou, Jie
Zhang, Yue
contents Catastrophic forgetting (CF) is a phenomenon that occurs in machine learning when a model forgets previously learned information while acquiring new knowledge for achieving a satisfactory performance in downstream tasks. As large language models (LLMs) have demonstrated remarkable performance, it is intriguing to investigate whether CF exists during the continual instruction tuning of LLMs. This study empirically evaluates the forgetting phenomenon in LLMs' knowledge during continual instruction tuning from the perspectives of domain knowledge, reasoning, and reading comprehension. The experiments reveal that catastrophic forgetting is generally observed in LLMs ranging from 1b to 7b parameters. Surprisingly, as the model scale increases, the severity of forgetting intensifies in such a model sale range which may result from the much significant initial performance in the larger LLM. Comparing the decoder-only model BLOOMZ with the encoder-decoder model mT0, BLOOMZ exhibits less forgetting and retains more knowledge. Interestingly, we also observe that LLMs can mitigate language biases, such as gender bias, during continual fine-tuning. Furthermore, our findings indicate that general instruction tuning can help alleviate the forgetting phenomenon in LLMs during subsequent fine-tuning.
format Preprint
id arxiv_https___arxiv_org_abs_2308_08747
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle An Empirical Study of Catastrophic Forgetting in Large Language Models During Continual Fine-tuning
Luo, Yun
Yang, Zhen
Meng, Fandong
Li, Yafu
Zhou, Jie
Zhang, Yue
Computation and Language
Catastrophic forgetting (CF) is a phenomenon that occurs in machine learning when a model forgets previously learned information while acquiring new knowledge for achieving a satisfactory performance in downstream tasks. As large language models (LLMs) have demonstrated remarkable performance, it is intriguing to investigate whether CF exists during the continual instruction tuning of LLMs. This study empirically evaluates the forgetting phenomenon in LLMs' knowledge during continual instruction tuning from the perspectives of domain knowledge, reasoning, and reading comprehension. The experiments reveal that catastrophic forgetting is generally observed in LLMs ranging from 1b to 7b parameters. Surprisingly, as the model scale increases, the severity of forgetting intensifies in such a model sale range which may result from the much significant initial performance in the larger LLM. Comparing the decoder-only model BLOOMZ with the encoder-decoder model mT0, BLOOMZ exhibits less forgetting and retains more knowledge. Interestingly, we also observe that LLMs can mitigate language biases, such as gender bias, during continual fine-tuning. Furthermore, our findings indicate that general instruction tuning can help alleviate the forgetting phenomenon in LLMs during subsequent fine-tuning.
title An Empirical Study of Catastrophic Forgetting in Large Language Models During Continual Fine-tuning
topic Computation and Language
url https://arxiv.org/abs/2308.08747