@inproceedings{prasertsom-etal-2026-recursive,
title = "Recursive numeral systems are highly regular and easy to process",
author = "Prasertsom, Ponrawee and
Silvi, Andrea and
Culbertson, Jennifer and
Dubhashi, Devdatt and
Johansson, Moa and
Smith, Kenny",
editor = "Demberg, Vera and
Inui, Kentaro and
Marquez, Llu{\'i}s",
booktitle = "Proceedings of the 19th Conference of the {E}uropean Chapter of the {A}ssociation for {C}omputational {L}inguistics (Volume 1: Long Papers)",
month = mar,
year = "2026",
address = "Rabat, Morocco",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.eacl-long.226/",
pages = "4873--4885",
ISBN = "979-8-89176-380-7",
abstract = "Much recent work has shown how cross-linguistic variation is constrained by competing pressures from efficient communication. However, little attention has been paid to the role of the systematicity of forms (*regularity*), a key property of natural language. Here, we demonstrate the importance of regularity in explaining the shape of linguistic systems by looking at recursive numeral systems. Previous work has argued that these systems optimise the trade-off between lexicon size and average morphosyntatic complexity (Deni{\'c} and Szymanik, 2024). However, showing that *only* natural-language-like systems optimise this trade-off has proven elusive, and existing solutions rely on ad-hoc constraints to rule out unnatural systems (Yang and Regier, 2025). Drawing on the Minimum Description Length (MDL) approach, we argue that recursive numeral systems are better viewed as efficient with regard to their regularity and processing complexity. We show that our MDL-based measures of regularity and processing complexity better capture the key differences between attested, natural systems and theoretically possible ones, including ``optimal'' recursive numeral systems from previous work, and that the ad-hoc constraintsnaturally follow from regularity. Our approach highlights the need to incorporate regularity across sets of forms in studies attempting tomeasure efficiency in language."
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<abstract>Much recent work has shown how cross-linguistic variation is constrained by competing pressures from efficient communication. However, little attention has been paid to the role of the systematicity of forms (*regularity*), a key property of natural language. Here, we demonstrate the importance of regularity in explaining the shape of linguistic systems by looking at recursive numeral systems. Previous work has argued that these systems optimise the trade-off between lexicon size and average morphosyntatic complexity (Denić and Szymanik, 2024). However, showing that *only* natural-language-like systems optimise this trade-off has proven elusive, and existing solutions rely on ad-hoc constraints to rule out unnatural systems (Yang and Regier, 2025). Drawing on the Minimum Description Length (MDL) approach, we argue that recursive numeral systems are better viewed as efficient with regard to their regularity and processing complexity. We show that our MDL-based measures of regularity and processing complexity better capture the key differences between attested, natural systems and theoretically possible ones, including “optimal” recursive numeral systems from previous work, and that the ad-hoc constraintsnaturally follow from regularity. Our approach highlights the need to incorporate regularity across sets of forms in studies attempting tomeasure efficiency in language.</abstract>
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%0 Conference Proceedings
%T Recursive numeral systems are highly regular and easy to process
%A Prasertsom, Ponrawee
%A Silvi, Andrea
%A Culbertson, Jennifer
%A Dubhashi, Devdatt
%A Johansson, Moa
%A Smith, Kenny
%Y Demberg, Vera
%Y Inui, Kentaro
%Y Marquez, Lluís
%S Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
%D 2026
%8 March
%I Association for Computational Linguistics
%C Rabat, Morocco
%@ 979-8-89176-380-7
%F prasertsom-etal-2026-recursive
%X Much recent work has shown how cross-linguistic variation is constrained by competing pressures from efficient communication. However, little attention has been paid to the role of the systematicity of forms (*regularity*), a key property of natural language. Here, we demonstrate the importance of regularity in explaining the shape of linguistic systems by looking at recursive numeral systems. Previous work has argued that these systems optimise the trade-off between lexicon size and average morphosyntatic complexity (Denić and Szymanik, 2024). However, showing that *only* natural-language-like systems optimise this trade-off has proven elusive, and existing solutions rely on ad-hoc constraints to rule out unnatural systems (Yang and Regier, 2025). Drawing on the Minimum Description Length (MDL) approach, we argue that recursive numeral systems are better viewed as efficient with regard to their regularity and processing complexity. We show that our MDL-based measures of regularity and processing complexity better capture the key differences between attested, natural systems and theoretically possible ones, including “optimal” recursive numeral systems from previous work, and that the ad-hoc constraintsnaturally follow from regularity. Our approach highlights the need to incorporate regularity across sets of forms in studies attempting tomeasure efficiency in language.
%U https://aclanthology.org/2026.eacl-long.226/
%P 4873-4885
Markdown (Informal)
[Recursive numeral systems are highly regular and easy to process](https://aclanthology.org/2026.eacl-long.226/) (Prasertsom et al., EACL 2026)
ACL
- Ponrawee Prasertsom, Andrea Silvi, Jennifer Culbertson, Devdatt Dubhashi, Moa Johansson, and Kenny Smith. 2026. Recursive numeral systems are highly regular and easy to process. In Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 4873–4885, Rabat, Morocco. Association for Computational Linguistics.