Syntactic trees and small-world networks: syntactic development as a dynamical process

Language has been argued to exhibit a complex system behavior. In our approach, the syntactic relations of dependency between words have been represented as networks. In a previous study, two English infants’ corpora of utterances were analyzed longitudinally, offering a view of the ontogeny of syntax. Abrupt changes were detected in the growth pattern of the Giant Connected Component – the largest connected set of nodes in a graph. In the present study, we have further analyzed and compared three more infants, from the CHILDES database, learning three different languages: Dutch, German and Spanish. Our results show, along with previous work with English-speaking infants, that all three infants’ syntactic networks change their topology in a similar way, from tree-like networks to small-world networks. This change happens at a similar period in all three infants (between ~700 and ~800 days), regardless of the language they acquire. Our study also shows that the hubs – the most connected nodes in these small-world networks – are always the so-called functional words, which, according to linguistic theory, just contribute to the syntactic structure of human language. The emergence of these hubs happens abruptly, following a logarithmic growth pattern. This developmental pattern challenges usage-based theories of language acquisition and suggests that syntactic development is driven by the growth of the lexicon.