The development of sentence planning.

This is an exploratory case study of the relation between speech output disturbances (dysfluencies) and the development of language production processes. The data consist of transcribed weekly speech samples of a Dutch boy between 2;4 and 2;11. The period of observation captures the early phase of the transition from 'pre-grammatical' to grammatical language. The frequency of occurrence of dysfluencies (i.e. repetitions, revisions and incomplete phrases) shows a significant increase and a subsequent decline. Whereas in the first half of the observation period the dysfluencies are distributed relatively randomly over sentences, in the second half they tend to concentrate in function words and sentence-initial words. The decline of dysfluency rate is shown to be related to an abundant use of a few 'syntactic frames'. It is argued that these results reflect the emergence of a component in the speech production apparatus which is specifically dedicated to serial-order planning.