# The optimality of syntactic dependency distances

arXiv: https://arxiv.org/abs/2007.15342 · HTML: https://mlsanity.com/paper/2007.15342/

## Key facts

- Cited by 15 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 30 Jul 2020.

## Built on by (most cited first, 15 of 15)

- [Linear-time calculation of the expected sum of edge lengths in random projective linearizations of trees](https://mlsanity.com/paper/2107.03277/) (2021)
- [The Linear Arrangement Library. A new tool for research on syntactic dependency structures](https://mlsanity.com/paper/2112.02512/) (2021)
- [The optimal placement of the head in the noun phrase. The case of demonstrative, numeral, adjective and noun](https://mlsanity.com/paper/2402.10311/) (2024)
- [The distribution of syntactic dependency distances](https://mlsanity.com/paper/2211.14620/) (2022)
- [Syntactic Language Change in English and German: Metrics, Parsers, and Convergences](https://mlsanity.com/paper/2402.11549/) (2024)
- [The expected sum of edge lengths in planar linearizations of trees. Theory and applications](https://mlsanity.com/paper/2207.05564/) (2022)
- [The optimality of word lengths. Theoretical foundations and an empirical study](https://mlsanity.com/paper/2208.10384/) (2022)
- [Predictability maximization and the origins of word order harmony](https://mlsanity.com/paper/2408.16570/) (2024)
- [How to measure the optimality of word or gesture order with respect to the principle of swap distance minimization](https://mlsanity.com/paper/2604.01938/) (2026)
- [Dependency distance minimization predicts compression](https://mlsanity.com/paper/2109.08900/) (2021)
- [The Maximum Linear Arrangement Problem for trees under projectivity and planarity](https://mlsanity.com/paper/2206.06924/) (2022)
- [Formal Constraints on Dependency Syntax](https://mlsanity.com/paper/2604.04542/) (2026)
- [Ease of dependency distance minimization in star-like structures](https://mlsanity.com/paper/2604.28034/) (2026)
- [Factors Influencing the Emergence of Dependency Length Minimization in Neural Agent Simulations](https://mlsanity.com/paper/2609.06025/) (2026)
- [Psychosis involves a deficit of information compression in connected speech](https://mlsanity.com/paper/2609.15522/) (2026)

## Abstract (arXiv)

It is often stated that human languages, as other biological systems, are shaped by cost-cutting pressures but, to what extent? Attempts to quantify the degree of optimality of languages by means of an optimality score have been scarce and focused mostly on English. Here we recast the problem of the optimality of the word order of a sentence as an optimization problem on a spatial network where the vertices are words, arcs indicate syntactic dependencies and the space is defined by the linear order of the words in the sentence. We introduce a new score to quantify the cognitive pressure to reduce the distance between linked words in a sentence. The analysis of sentences from 93 languages representing 19 linguistic families reveals that half of languages are optimized to a 70% or more. The score indicates that distances are not significantly reduced in a few languages and confirms two theoretical predictions, i.e. that longer sentences are more optimized and that distances are more likely to be longer than expected by chance in short sentences. We present a new hierarchical ranking of languages by their degree of optimization. The new score has implications for various fields of language research (dependency linguistics, typology, historical linguistics, clinical linguistics and cognitive science). Finally, the principles behind the design of the score have implications for network science.