Adapting Large Language Models for Character-based Augmentative and Alternative Communication

Dylan Gaines, Keith Vertanen


Abstract
Users of Augmentative and Alternative Communication (AAC) may write letter-by-letter via an interface that uses a character language model. However, most state-of-the-art large pretrained language models predict subword tokens of variable length. We investigate how to practically use such models to make accurate and efficient character predictions. Our algorithm for producing character predictions from a subword large language model (LLM) provides more accurate predictions than using a classification layer, a byte-level LLM, or an n-gram model. Additionally, we investigate a domain adaptation procedure based on a large dataset of sentences we curated based on scoring how useful each sentence might be for spoken or written AAC communication. We find our procedure further improves model performance on simple, conversational text.
Anthology ID:
2025.findings-emnlp.826
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2025
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
15273–15291
Language:
URL:
https://preview.aclanthology.org/author-page-yu-wang-polytechnic/2025.findings-emnlp.826/
DOI:
10.18653/v1/2025.findings-emnlp.826
Bibkey:
Cite (ACL):
Dylan Gaines and Keith Vertanen. 2025. Adapting Large Language Models for Character-based Augmentative and Alternative Communication. In Findings of the Association for Computational Linguistics: EMNLP 2025, pages 15273–15291, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
Adapting Large Language Models for Character-based Augmentative and Alternative Communication (Gaines & Vertanen, Findings 2025)
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PDF:
https://preview.aclanthology.org/author-page-yu-wang-polytechnic/2025.findings-emnlp.826.pdf
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