What bilingualism demands

Abstract

Abstract Bilingualism research sits at the intersection of linguistics, cognitive neuroscience, and psychology, yet these disciplines often operate in relative isolation, limiting explanatory power and theoretical progress. This paper argues that deeper, more purposeful cross-fertilization among these fields is both possible and necessary to address some of the most pressing questions in the study of bilingualism. After establishing a shared foundation through a concise history of mind–brain–language inquiry, we outline the componential architecture of language — spanning phonology, syntax, morphology, semantics, and pragmatics — to underscore the linguistic sophistication required for meaningful neuroscientific investigation. We then review the neuroanatomical substrates of language representation, processing, and cognitive control, emphasizing distributed network models over classical localizationist accounts. The contribution of electroencephalography (EEG) is examined, including event-related potentials, oscillatory dynamics, and resting-state measures, highlighting their capacity to capture how bilingual experience reshapes linguistic processing and neural function over time and at the individual level. Two exemplars operationalize our convergence argument. Exemplar 1 demonstrates how early brain states measured via EEG can predict individual differences in bilingual linguistic developmental trajectories, offering prospective, mechanistic insights that retrospective adult studies cannot. Exemplar 2 illustrates how linguistically principled formalization of relative linguistic typological distance (RLTD) is indispensable for studies seeking to link cross-language structural differences to bilingualism-induced neurocognitive adaptations. Together, these cases show that linguistics needs neuroscience to ground its constructs in neural mechanisms, while neuroscience needs linguistics to properly characterize what is being processed. Genuine interdisciplinary integration, not parallel inquiry, is the path forward for bilingualism research.