The Interface Hypothesis (Sorace and Filiaci, 2006) conjectures that adult second language learners (L2 learners) who have reached near-native levels of proficiency in their second language exhibit difficulties at the interface between syntax and other cognitive domains, most notably at the syntax-discourse interface. However, research in this area was limited, in that the data were offline, and thus unable to provide evidence for the nature of the deficit shown by L2 learners. This thesis presents online data which address the question of the underlying nature of the difficulties observed in L2 learners at the syntaxdiscourse interface. This thesis has extended work on the syntax-discourse interface in L2 learners by investigating the acquisition of two phenomena at the syntax-discourse interface in German: the role of word order and pronominalization with respect to information structure (Experiments 1-3), and the antecedent preferences of anaphoric demonstrative (the der, die, das series homophonous with the definite article) and personal pronouns (the er, sie, es series) (Experiments 4- 8). Crucially, this work has used an on-line methodology, the visual-world paradigm, which allows an insight into the incremental interpretation of interface phenomena in real-time processing. The data from these experiments show that L2 learners have difficulty integrating different sources of information in real-time comprehension efficiently, supporting the Interface Hypothesis. However, the nature of the processing difficulties which L2 learners demonstrate in on-line processing was not determined by these studies, resulting in the question: are L2 learners’ difficulties a result of a limitation of processing resources, or the inability to deploy those resources effectively? A novel dualtask experiment (Experiment 9), in which native speakers of German were placed under processing load simulated the results previously obtained for L2 learners. It is concluded that syntactic dependencies were constrained by resource limitation, whereas discourse based dependencies were constrained by processing resource allocation.

This thesis focuses on the cross-linguistic differences between Italian and Spanish regarding the pragmatic restrictions on the resolution of null and overt subject pronouns (NS and OSP). It also tries to identify possible links between such cross-linguistic differences and morpho-syntactic differences at the level of the verbal morphology of the two languages. Spanish and Italian are typologically related and morpho-syntactically similar and have been assumed to instantiate the same setting of the NS parameter with respect to not only its syntactic licensing conditions, but also the pragmatic constraints determining the distribution of null and overt subject pronouns, and this assumption has had important implications for cross-linguistic research. The first aim of this study was to test directly for the first time the assumption about the equivalence of Italian and Spanish; in order to do so, I run a series of self-paced reading experiments using the same materials translated in each language, so that the results were directly comparable. The experiments were based on Carminati’s (2002) study on antecedent preferences for Italian NSs and OSPs in intra-sentential anaphora, testing the Position of Antecedent Strategy. The results suggest that while in Italian there is a strict division of labour between NS and OSP (confirming Carminati’s findings), this division is not as clear-cut in Spanish. More precisely, while Italian personal pronouns unambiguously signal a switch in subject reference, the association between OSPs and switch reference seems to be much weaker in Spanish. These results, which are interpreted in terms of Cardinaletti and Starke’s (1999) cross-linguistic typology of deficient pronouns, highlight an asymmetry between the strength of NS and OSP biases in Spanish that could not have emerged through the traditional methodology used by the numerous variationist studies on the subject, based on corpus analysis. A subsequent pair of experiments tested the hypothesis that the cross-linguistic differences attested might be related to the relative syncretism of the Spanish verbal morphology compared to the Italian one with regard to the unambiguous expression of person features on the verbal head. The results only provided weak support for the hypothesis, although they did confirm the presence of the cross- linguistic differences in the processing and resolution of anaphoric NS and OSP dependencies revealed by the previous experiments.

Previous accounts of preverbal subjects in Spanish and European Portuguese (EP) in the literature have debated the syntactic position of these elements. According to some analyses, preverbal subjects are canonical arguments appearing in an A-position (e.g. Goodall 2001, 2002; Suñer 2003 for Spanish; Duarte 1997; Costa 2004 for EP). Other analyses propose that preverbal subjects are non-arguments appearing in a left-peripheral - perhaps CLLD - A'-position (e.g. Uribe-Etxebarria 1990, 1995; Ordóñez & Treviño 1999 for Spanish; Barbosa 1996, 2000 for EP). Although Galician is an ideal language for insight on this debate due to linguistic ties with EP and political ties with Spain, Gupton (2006) obtained inconclusive results regarding the status of preverbal subjects in Galician. As the literature on Galician lacks descriptions of preferred word orders according to discourse context, I collected quantitative and qualitative experimental data to describe the syntax-information structure interface in Galician. The vast majority of speakers of this minority language are Spanish-Galician bilinguals with (self-reported) high levels of competency in both languages. This is of relevance because a variety of bilinguals, including heritage speakers, attrited L1 speakers, and those who have been claimed to have incompletely acquired the heritage language have been shown to exhibit instability and optionality at the linguistic interfaces, in particular at the syntax-discourse pragmatics interface (e.g. Hulk & Müller 2000; Sorace 2005 among numerous others), which is the subject of investigation in this dissertation. The data collected indicate a marked preference for SVO in a wide variety of discourse contexts, a preference that differs from those claimed to apply in similar contexts in Spanish (e.g. Ordóñez 1997, Zubizarreta 1998, Casielles 2004). Assuming that the presence of clitics implies the projection of f (Raposo & Uriagereka 2005) and the extension of the preverbal field into the left periphery, the cliticization data gathered for Galician in main clauses, subordinate clauses and recomplementation contexts suggest a number of preverbal positions in which preverbal subjects, affective phrases, and Topic elements may appear, one of which I suggest is Spec, DoubledFceP, following Martín-González (2002), but with proposed modifications. The data also suggest necessary modifications for López's (2009) syntax-information structure interface proposal in Romance, which suggests a reduced, syncretic left-peripheral position (Spec, FinP) in which CLLD Topics, wh- elements, and Fronted Focus elements appear and are assigned [+c] (contrastive) by the Pragmatics module. Within the preverbal architecture I propose, preverbal subjects and other left-peripheral elements coincide, but in a variety of syntactic positions. Therefore, for pragmatic feature assignment to successfully assign [+c], Pragmatics must distinguish between preverbal subjects and other left-peripheral phrases.