Jumping into syntax:Transitions in the development of closed class words

Over the years, the study of language development has been syntax oriented. In this paper, we present a non-linear approach to highlight quantitative processes in language development. First, we used a continuous model, i.e. growth theory, to fit data. Second, catastrophe theory was applied to test whether discontinuities occur in language development. That is, this theory offers criteria for a reorganization of a specific rule or structure (e.g. in language development). These criteria, or flags, have been applied to longitudinally collected and spontaneous data of six Dutch-speaking children. The development of function (or closed class) words is supposed to be sudden, resulting in a rapid change from telegraphic to differentiated speech. We found evidence for such change, and the presence of multimodality. Although other flags could not be found, we argued that in the third year of life, i.e. around the introduction of function words in the speech of a child, several linguistic and non-linguistic factors are changing. We conclude that there is no strong evidence for catastrophic change in language development. We also discuss the question of what the patterns in language development refer to, i.e. what they mean with respect to underlying structures