Language Repertoire and Mental Health in the Elderly

This article introduces an ongoing interdisciplinary project that investigates how the language repertoire—conceived not as a set of named “languages” but as a structured inventory of linguistic signs—relates to cognitive functioning in older adults. Since the 1960s, research on bilingualism and cognition, and later on bilingualism and dementia, has yielded markedly discordant results: some studies report protective or enhancing effects, others find null or even contradictory effects. We argue that this persistent dissonance stems from two foundational errors: (1) reliance on a now-revised neuroscientific paradigm of narrowly constrained plasticity, and (2) a linguistic category mistake—treating glossonyms (named “languages”) and the construct “bilingualism” as neurocognitively valid units. We propose an alternative, sign- and neurosynapse-based framework in which the brain, at a Brain–Environment Interface (BEI), processes, organizes, and dynamically retains signals (signs) irrespective of language labels. Methodologically, we operationalize language repertoire as the structure and extent of sign systems, quantified via valence-based testing and a composite repertoire index (lr), rather than counts of “languages.” Preliminary findings from our year-long clinical survey indicate systematic relationships between repertoire metrics and cognitive performance, while also revealing limitations of conventional dementia screenings that are insensitive to repertoire structure. These results motivate a paradigm shift from binary bilingualism metrics toward neurostructurally grounded measures of linguistic experience and processing.