Predictability maximization and the origins of word order harmony

TL;DR

This paper explores how the placement of a head in a sequence affects predictability, revealing that harmonic order maximizes overall predictability and explaining why languages favor certain word orders.

Contribution

It introduces an information theoretic framework to explain the origins of word order harmony based on predictability maximization strategies.

Findings

Harmonic order maximizes sequence predictability.

Postponing the head optimizes its predictability.

Moving the head forward optimizes dependents' predictability.

Abstract

We address the linguistic problem of the sequential arrangement of a head and its dependents from an information theoretic perspective. In particular, we consider the optimal placement of a head that maximizes the predictability of the sequence. We assume that dependents are statistically independent given a head, in line with the open-choice principle and the core assumptions of dependency grammar. We demonstrate the optimality of harmonic order, i.e., placing the head last maximizes the predictability of the head whereas placing the head first maximizes the predictability of dependents. We also show that postponing the head is the optimal strategy to maximize its predictability while bringing it forward is the optimal strategy to maximize the predictability of dependents. We unravel the advantages of the strategy of maximizing the predictability of the head over maximizing the predictability of dependents. Our findings shed light on the placements of the head adopted by real languages or emerging in different kinds of experiments.