(Re)thinking the Interface Hypothesis and its implications for language teaching

The interface between syntax and other domains has recently become a key area of interest in Generative Second Language Acquisition (GenSLA). Much of the research on linguistic interfaces has been influenced by the Interface Hypothesis (IH), which was proposed by Sorace & Filiaci (2006) in an attempt to explain the non-target-like behaviour found at very advanced stages of second language (L2) acquisition. Originally, the IH claimed that narrow syntactic properties are acquirable, whereas properties at the interface between syntax and other domains may not be fully acquirable (cf. Sorace & Filiaci, 2006). In its most recent version, the IH specifies that properties at grammar-external interfaces (i.e. interfaces which connect the grammar to external domains) are more likely to be a source of problems in end-state grammars than properties involving grammar-internal interfaces (i.e. interfaces which link different modules within the grammar) (cf. Sorace & Serratrice, 2009; Tsimpli & Sorace, 2006; Sorace, 2011). The IH is, therefore, an account of non-target patterns at the level of ultimate attainment.