The development of finiteness from a lexical to a functional category
Finiteness in adult Dutch is expressed by use of formal means of morpho-syntax, i.e. with both inflectional morphology and word order (verb-second). These formal means are linked to a projection of the functional category FIN as in:
FIN
SpecFIN FIN
FIN VP
SpecVP VP
At the initial stage of acquisition, there is no productive use of functional elements nor do learner languages have verb-second. This is due to the fact that initially learner languages are systems in which the functional category FIN is absent. Properties of validation and anchoring are expressed by lexical means: Expression of illocutionary force occurs with modal predicates, contextual anchoring is expressed with deictic elements. Instantiation of the functional projection FIN is caused by the acquisition of the auxiliary verb heb/heeft (have/has). As a functional category, AUX provides a position for functional elements to express modal or – in the default case – non-modal illocutionary force. With the instantiation of AUX, the initial, i.e. specifier position serves as a position for elements with topic function, i.e. for elements used to establish contextual anchoring of the utterance. The acquisition of AUX is the driving force in the development from the lexical to the functional stage. However, the acquisition of AUX does not come as a deus ex machina. Structures with AUX are learned for reasons of information processing. Utterances with an auxiliary are typically used as a topicalisation device. Due to the fact that structures with AUX are learned as a topicalisation device, it seems possible (1) to provide a functional explanation for why auxiliaries, inversion and subject pronouns are learned simultaneously and (2) to account for the fact that the acquisition process occurs similarly in both L1- and L2-learner languages.