Testing the Interface Hypothesis: The case of auxiliary change under restructuring in L2 Italian

The Interface Hypothesis predicts that narrow syntactic properties can be completely acquired in the L2, whereas this may not be possible for interface properties involving syntax and another cognitive domain (Sorace & Filiaci 2006). In the study reported in this paper we test the aspect of the Interface Hypothesis pertaining to narrow syntax by looking at the ultimate attainment of the purely syntactic aspect of auxiliary change under restructuring in Italian in L2 acquisition. Restructuring constructions in Italian involve modal, aspectual or motion verbs taking infinitival complements (Rizzi 1978). When the embedded verb in these constructions is unaccusative and requires essere (‘be’), the main verb (normally taking avere, ‘have’) can optionally also take essere (Lui ha/è voluto andare a casa, ‘He wanted to go home’). In the presence of clitic climbing, the shift from one auxiliary to the other is obligatory (Lui ci *ha/è voluto andare, ‘He wanted to go there’). Similarly to constructions without clitics, constructions with the clitic in situ also exhibit optionality (Lui ha/è voluto andarci, ‘He wanted to go there’). Auxiliary change is thus sometimes optional and sometimes obligatory in restructuring constructions with unaccusative complements, depending on a purely syntactic factor: the presence and the placement of the clitic