How Syntax Specialization Emerges in Language Models

Fuente: arXiv
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Autori principali: Duan, Xufeng, Yao, Zhaoqian, Zhang, Yunhao, Wang, Shaonan, Cai, Zhenguang G.
Natura: Preprint
Pubblicazione: 2025
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author Duan, Xufeng
Yao, Zhaoqian
Zhang, Yunhao
Wang, Shaonan
Cai, Zhenguang G.
author_facet Duan, Xufeng
Yao, Zhaoqian
Zhang, Yunhao
Wang, Shaonan
Cai, Zhenguang G.
contents Large language models (LLMs) have been found to develop surprising internal specializations: Individual neurons, attention heads, and circuits become selectively sensitive to syntactic structure, reflecting patterns observed in the human brain. While this specialization is well-documented, how it emerges during training and what influences its development remains largely unknown. In this work, we tap into the black box of specialization by tracking its formation over time. By quantifying internal syntactic consistency across minimal pairs from various syntactic phenomena, we identify a clear developmental trajectory: Syntactic sensitivity emerges gradually, concentrates in specific layers, and exhibits a 'critical period' of rapid internal specialization. This process is consistent across architectures and initialization parameters (e.g., random seeds), and is influenced by model scale and training data. We therefore reveal not only where syntax arises in LLMs but also how some models internalize it during training. To support future research, we will release the code, models, and training checkpoints upon acceptance.
format Preprint
id arxiv_https___arxiv_org_abs_2505_19548
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle How Syntax Specialization Emerges in Language Models
Duan, Xufeng
Yao, Zhaoqian
Zhang, Yunhao
Wang, Shaonan
Cai, Zhenguang G.
Computation and Language
Artificial Intelligence
Large language models (LLMs) have been found to develop surprising internal specializations: Individual neurons, attention heads, and circuits become selectively sensitive to syntactic structure, reflecting patterns observed in the human brain. While this specialization is well-documented, how it emerges during training and what influences its development remains largely unknown. In this work, we tap into the black box of specialization by tracking its formation over time. By quantifying internal syntactic consistency across minimal pairs from various syntactic phenomena, we identify a clear developmental trajectory: Syntactic sensitivity emerges gradually, concentrates in specific layers, and exhibits a 'critical period' of rapid internal specialization. This process is consistent across architectures and initialization parameters (e.g., random seeds), and is influenced by model scale and training data. We therefore reveal not only where syntax arises in LLMs but also how some models internalize it during training. To support future research, we will release the code, models, and training checkpoints upon acceptance.
title How Syntax Specialization Emerges in Language Models
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2505.19548