Abstract

The core architecture of systemic functional linguistics (SFL) assumes monolingual individuals and scenarios. As such, it overlooks the intra- and inter-stratal particularities of bilinguals, who account for more than half the world’s population. Critical questions thus arise that require expanding the theory’s transdisciplinary scope. How are the two languages of bilinguals organized and processed across phonological, lexico-grammatical, and semantic strata? What kinds of interactions, if any, must be acknowledged between them? And how are bilingual language systems affected by individuals’ linguistic histories? Here we aim to address these questions, drawing from psycholinguistics and neurolinguistics. First, we survey the phenomenon of bilingualism and its role in the theoretical landscape of SFL. Second, we review critical (neuro)cognitive evidence on core differences and interactions between bilinguals’ first and second languages, considering phonological, lexico-grammatical, and semantic phenomena. Third, we consider how such patterns vary depending on second-language proficiency, age of appropriation, and degree of second-language exposure. Finally, we outline the main theoretical constraints and challenges that such evidence poses toward a cognitively oriented, individual-centered SFL account of bilingualism. This dialogue, we propose, can broaden the theory’s descriptive and applicable scope while prompting new insights on bilingualism at large.