How Do Language Models Acquire Character-Level Information?

Fuente: arXiv
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Autores principales: Sato, Soma, Sasano, Ryohei
Formato: Preprint
Publicado: 2026
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author Sato, Soma
Sasano, Ryohei
author_facet Sato, Soma
Sasano, Ryohei
contents Language models (LMs) have been reported to implicitly encode character-level information, despite not being explicitly provided during training. However, the mechanisms underlying this phenomenon remain largely unexplored. To reveal the mechanisms, we analyze how models acquire character-level knowledge by comparing LMs trained under controlled settings, such as specifying the pre-training dataset or tokenizer, with those trained under standard settings. We categorize the contributing factors into those independent of tokenization. Our analysis reveals that merge rules and orthographic constraints constitute primary factors arising from tokenization, whereas semantic associations of substrings and syntactic information function as key factors independent of tokenization.
format Preprint
id arxiv_https___arxiv_org_abs_2602_05347
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle How Do Language Models Acquire Character-Level Information?
Sato, Soma
Sasano, Ryohei
Computation and Language
Language models (LMs) have been reported to implicitly encode character-level information, despite not being explicitly provided during training. However, the mechanisms underlying this phenomenon remain largely unexplored. To reveal the mechanisms, we analyze how models acquire character-level knowledge by comparing LMs trained under controlled settings, such as specifying the pre-training dataset or tokenizer, with those trained under standard settings. We categorize the contributing factors into those independent of tokenization. Our analysis reveals that merge rules and orthographic constraints constitute primary factors arising from tokenization, whereas semantic associations of substrings and syntactic information function as key factors independent of tokenization.
title How Do Language Models Acquire Character-Level Information?
topic Computation and Language
url https://arxiv.org/abs/2602.05347