This book investigates the acquisition of syntactic and discursive properties by adult learners of non-native Spanish. In particular, two properties of the pro-drop parameter are explored: overt and null pronominal subjects and unaccusative subject-verb inversion. These two properties are constrained by syntactic (formal) properties of Universal Grammar (UG) and, at the same time, by language-specific discursive properties (topic and focus). The study argues that formal and syntactic properties which are constrained by UG are acquired earlier than discursive properties, which pose persistent problems for learners. Results from experiments on pronominal subjects and word order confirm that both English and Greek advanced learners of non-native Spanish show convergent (native-like) intuitions with respect to the syntactic and formal principles of UG, while showing divergent and optional intuitions with language-specific discursive properties (information structure: topic and focus).