Revisiting the Estimation of Unigram Surprisal in Computational Psycholinguistics

Zachary Hopton, Francesco Ignazio Re, Samuel Kiegeland, Andreas Opedal, Eleanor Chodroff, Ryan Cotterell


Abstract
Contextual and unigram surprisal are standard predictors of reading time in computational psycholinguistics. While contextual surprisal is typically derived from neural language models, unigram surprisal is usually obtained from independent corpus counts. Although both quantities are deterministic functionals of a single underlying distribution—capturing conditional and marginal structure respectively—this practice breaks their probabilistic link and may introduce estimation error from the mismatch. We propose three principles for estimating unigram surprisal in psycholinguistic research, including the requirement that both quantities be derived from the same language model. We operationalize this principle by introducing a Monte Carlo estimator of unigram surprisal from a language model, along with a marginalized variant that has lower variance empirically. When unigram surprisal is re-estimated under this unified framework, we find evidence that predictors change in their predictive contribution to reading time. We also confirm prior findings that frequency can be a stronger predictor of processing effort than contextual surprisal under this unified framework.
Anthology ID:
2026.emnlp-main.2399
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
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SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
54526–54554
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2399/
DOI:
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Cite (ACL):
Zachary Hopton, Francesco Ignazio Re, Samuel Kiegeland, Andreas Opedal, Eleanor Chodroff, and Ryan Cotterell. 2026. Revisiting the Estimation of Unigram Surprisal in Computational Psycholinguistics. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 54526–54554, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Revisiting the Estimation of Unigram Surprisal in Computational Psycholinguistics (Hopton et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2399.pdf