The changing status of 'filler syllables' on the way to grammatical morphemes.

The appearance of 'filler syllables' (called here PAEs, for Prefixed Additional Elements) in the late single-word period is analysed in relation to the emergence of grammatical morphemes, by confronting data from the longitudinal study of one child acquiring French, video-recorded between 1;3.2 and 2;2.6, with four hypotheses making different claims about the kind of language knowledge underlying their production: the devices to lengthen single-word utterances, the syntactic slots, the selectivity of occurrence, and the organization of surface regularities hypotheses. The pattern of results concerning the first two to three months' production of PAEs points to the existence of a premorphological period in which PAEs result from the organization of phonoprosodic regularities of the language rather than being constrained by structural rules relative to syntactic slots or to the class of the word they precede. This premorphological period is followed by a protomorphological one in which incipient properties of grammatical morphemes and of word classes start to appear at the same time.