Words, Subwords, and Morphemes: What Really Matters in the Surprisal-Reading Time Relationship?

Sathvik Nair, Philip Resnik


Abstract
An important assumption that comes with using LLMs on psycholinguistic data has gone unverified. LLM-based predictions are based on subword tokenization, not decomposition of words into morphemes. Does that matter? We carefully test this by comparing surprisal estimates using orthographic, morphological, and BPE tokenization against reading time data. Our results replicate previous findings and provide evidence that *in the aggregate*, predictions using BPE tokenization do not suffer relative to morphological and orthographic segmentation. However, a finer-grained analysis points to potential issues with relying on BPE-based tokenization, as well as providing promising results involving morphologically-aware surprisal estimates and suggesting a new method for evaluating morphological prediction.
Anthology ID:
2023.findings-emnlp.752
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2023
Month:
December
Year:
2023
Address:
Singapore
Editors:
Houda Bouamor, Juan Pino, Kalika Bali
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
11251–11260
Language:
URL:
https://aclanthology.org/2023.findings-emnlp.752
DOI:
10.18653/v1/2023.findings-emnlp.752
Bibkey:
Cite (ACL):
Sathvik Nair and Philip Resnik. 2023. Words, Subwords, and Morphemes: What Really Matters in the Surprisal-Reading Time Relationship?. In Findings of the Association for Computational Linguistics: EMNLP 2023, pages 11251–11260, Singapore. Association for Computational Linguistics.
Cite (Informal):
Words, Subwords, and Morphemes: What Really Matters in the Surprisal-Reading Time Relationship? (Nair & Resnik, Findings 2023)
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PDF:
https://aclanthology.org/2023.findings-emnlp.752.pdf