Closed class words in motion:An application of catastrophe theory to language development

In this paper, catastrophe theory is used to decide whether or not the sudden introduction of so called closed class words in the language of a child is a discontinuous change. On the basis of the spontaneous language of six Dutch children, four 'flags' were translated into empirical indicators. Empirical evidence only supports a rapid introduction of function words (i.e. a sudden jump) and multimodality, not a phase transition. This sudden change is accompanied by other features (e.g. by temporal dysfluencies). Explanations about order and form of development are based on linguistic theories, and the relationship between non-linear models and psycholinguistic models needs To be explicated.