Heritage language proficiency does not predict syntactic CLI into L3 English

This study examines cross-linguistic influence (CLI) in the acquisition of embedded wh-questions in L3 English in German-dominant heritage speakers (HSs) of Italian. Specifically, we investigate whether a higher proficiency in the heritage language Italian increases the potential for CLI from that language. To this end, 21 adult-aged Italian-German early bilinguals and 32 monolingual controls (L1 speakers of Italian, German, or English) completed an acceptability judgement task that tested the acquisition of embedded wh-questions in English (while also controlling for the acquisition of the relevant properties in German and Italian). Language dominance was assessed using a yes/no vocabulary test and a proficiency index based on various aspects of self-reported language use and proficiency. Our results suggest that syntactic CLI occurs from both languages and that this is unrelated to overall dominance in German or proficiency in Italian.