a1 University of Paris Ouest Nanterre La Défense How do French
children acquire the grammatical system of their native language
so easily? Many hypotheses have been put forward and
experimentally tested to solve this mystery. Generative theories
argue that grammar is a universal and innate ability ready to be
instantiated after birth. Within this framework, grammatical
development is seen as a process whereby universal grammar
gradually settles into the language-specific structures of the
linguistic input that children receive in the first years of
life. In the last decades however, many researchers of child
language development have suggested other explanations. Current
functional-cognitive research (cf. Langacker, 1988, 2000; Bybee,
1995, 2002; Elman et al., 1996; Tomasello, 2003; Diessel, 2004),
proposes a usage-based approach to first language acquisition,
where grammar is shaped by usage, and linguistic constructions
are taken from parental input and gradually generalised by the
child. Usage-based theori