# How communicatively optimal are exact numeral systems? Once more on lexicon size and morphosyntactic complexity

arXiv: https://arxiv.org/abs/2602.20372 · HTML: https://mlsanity.com/paper/2602.20372/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 5 of its 43 references that are in the map.
- First posted on arXiv 23 Feb 2026.

## Builds on (most cited first, 5 of 5)

- [Practical Bayesian model evaluation using leave-one-out cross-validation and WAIC](https://mlsanity.com/paper/1507.04544/) (2015)
- [Morphological Irregularity Correlates with Frequency](https://mlsanity.com/paper/1906.11483/) (2019)
- [Annotating and Inferring Compositional Structures in Numeral Systems Across Languages](https://mlsanity.com/paper/2503.01625/) (2025)
- [Recursive numeral systems are highly regular and easy to process](https://mlsanity.com/paper/2510.27049/) (2025)
- [Complexity counts: global and local perspectives on Indo-Aryan numeral systems](https://mlsanity.com/paper/2505.21510/) (2025)

## Abstract (arXiv)

Recent research argues that exact recursive numeral systems optimize communicative efficiency by balancing a tradeoff between the size of the numeral lexicon and the average morphosyntactic complexity (roughly length in morphemes) of numeral terms. We argue that previous studies have not characterized the data in a fashion that accounts for the degree of complexity languages display. Using data from 52 genetically diverse languages and an annotation scheme distinguishing between predictable and unpredictable allomorphy (formal variation), we show that many of the world's languages are decisively less efficient than one would expect. We discuss the implications of our findings for the study of numeral systems and linguistic evolution more generally.