Beyond Induction Heads: In-Context Meta Learning Induces Multi-Phase Circuit Emergence

Fuente: arXiv
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Main Authors: Minegishi, Gouki, Furuta, Hiroki, Taniguchi, Shohei, Iwasawa, Yusuke, Matsuo, Yutaka
Format: Preprint
Published: 2025
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author Minegishi, Gouki
Furuta, Hiroki
Taniguchi, Shohei
Iwasawa, Yusuke
Matsuo, Yutaka
author_facet Minegishi, Gouki
Furuta, Hiroki
Taniguchi, Shohei
Iwasawa, Yusuke
Matsuo, Yutaka
contents Transformer-based language models exhibit In-Context Learning (ICL), where predictions are made adaptively based on context. While prior work links induction heads to ICL through a sudden jump in accuracy, this can only account for ICL when the answer is included within the context. However, an important property of practical ICL in large language models is the ability to meta-learn how to solve tasks from context, rather than just copying answers from context; how such an ability is obtained during training is largely unexplored. In this paper, we experimentally clarify how such meta-learning ability is acquired by analyzing the dynamics of the model's circuit during training. Specifically, we extend the copy task from previous research into an In-Context Meta Learning setting, where models must infer a task from examples to answer queries. Interestingly, in this setting, we find that there are multiple phases in the process of acquiring such abilities, and that a unique circuit emerges in each phase, contrasting with the single-phases change in induction heads. The emergence of such circuits can be related to several phenomena known in large language models, and our analysis lead to a deeper understanding of the source of the transformer's ICL ability.
format Preprint
id arxiv_https___arxiv_org_abs_2505_16694
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Beyond Induction Heads: In-Context Meta Learning Induces Multi-Phase Circuit Emergence
Minegishi, Gouki
Furuta, Hiroki
Taniguchi, Shohei
Iwasawa, Yusuke
Matsuo, Yutaka
Computation and Language
Artificial Intelligence
Transformer-based language models exhibit In-Context Learning (ICL), where predictions are made adaptively based on context. While prior work links induction heads to ICL through a sudden jump in accuracy, this can only account for ICL when the answer is included within the context. However, an important property of practical ICL in large language models is the ability to meta-learn how to solve tasks from context, rather than just copying answers from context; how such an ability is obtained during training is largely unexplored. In this paper, we experimentally clarify how such meta-learning ability is acquired by analyzing the dynamics of the model's circuit during training. Specifically, we extend the copy task from previous research into an In-Context Meta Learning setting, where models must infer a task from examples to answer queries. Interestingly, in this setting, we find that there are multiple phases in the process of acquiring such abilities, and that a unique circuit emerges in each phase, contrasting with the single-phases change in induction heads. The emergence of such circuits can be related to several phenomena known in large language models, and our analysis lead to a deeper understanding of the source of the transformer's ICL ability.
title Beyond Induction Heads: In-Context Meta Learning Induces Multi-Phase Circuit Emergence
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2505.16694