  While natural languages differ widely in both canonical word order and word
order flexibility, their word orders still follow shared cross-linguistic
statistical patterns, often attributed to functional pressures. In the effort
to identify these pressures, prior work has compared real and counterfactual
word orders. Yet one functional pressure has been overlooked in such
investigations: the uniform information density (UID) hypothesis, which holds
that information should be spread evenly throughout an utterance. Here, we ask
whether a pressure for UID may have influenced word order patterns
cross-linguistically. To this end, we use computational models to test whether
real orders lead to greater information uniformity than counterfactual orders.
In our empirical study of 10 typologically diverse languages, we find that: (i)
among SVO languages, real word orders consistently have greater uniformity than
reverse word orders, and (ii) only linguistically implausible counterfactual
orders consistently exceed the uniformity of real orders. These findings are
compatible with a pressure for information uniformity in the development and
usage of natural languages.
