Non-configurationality in diachrony correlations in local and global networks of ancient Greek and Latin

Non-configurationality is a linguistic property associated with free word order,
discontinuous constituents, including NPs, and null anaphora of referential
arguments. Quantitative metrics, based both on local networks (syntactic trees
and word order within sentences) and on global networks (incorporating the
relations within a whole treebank into a shared graph), can reveal correlations
among these features. Using treebanks we focus on diachronic varieties
of Ancient Greek and Latin, in which non-configurationality tapered off over
time, leading to the largely configurational nature of the Romance languages
and of Modern Greek. A property of global networks (density of their spectra
around zero eigenvalues) measuring the regularity in word order is shown to be
strengthened from classical to late varieties. Discontinuous NPs are traced by
counting the words creating non-projectivity in dependency trees: these drop
dramatically in late varieties. Finally, developments in the use of null referential
direct objects are gauged by assessing the percentage of third-person personal
pronouns among verb objects. All three features turn out to change over time
due to the decay of non-configurationality. Evaluation of the strength of their
pairwise correlation shows that null direct objects and discontinuous NPs are
deeply intertwined.