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Aptitude, not polyglotism, is associated with efficient activation in core language areas.
Poster Session A, Wednesday, September 30, 11:00 am - 1:00 pm, Wangari Maathai
Irene Balboni1,2, Olga Kepinska3,4,5,6, Alessandra Rampinini1, Raphael Berthele2, Narly Golestani1,3,4; 1Department of Psychology, Faculty of Psychology and Education Science, University of Geneva, Geneva, Switzerland, 2Institute of Multilingualism, University of Fribourg, Fribourg, Switzerland, 3Department of Developmental and Educational Psychology Faculty of Psychology, Faculty of Psychology, University of Vienna, Vienna, Austria, 4Department of Behavioural and Cognitive Biology, Faculty of Life Sciences, University of Vienna, Vienna, Austria, 5Laboratoire Parole et Langage (LPL), CNRS, Aix Marseille Univ, Aix-en-Provence, France, 6Institute of Language Communication and the Brain (ILCB), Aix-en-Provence, France
Individual differences in language abilities have long fascinated researchers, yet the neurobiological mechanisms underlying extraordinary multilingualism remain poorly understood. Prior work documented distinctive morphological and functional characteristics of perisylvian brain hubs in multilingual individuals whose language skills exceed environmental demands. However, conclusions from this literature are constrained by several methodological and conceptual choices. Studies relied predominantly on region-of-interest analyses confined to cortical language hubs, missing multilingual adaptations that could take place across the whole brain. Second, binary group comparisons between polyglots and controls fail to capture the graded, continuous nature of multilingualism. Third, previous studies having used a language localizer only report intact versus degraded speech contrasts, precluding examination of neural resources underlying degraded speech processing, which, although unintelligible, may engage the language network in polyglot or apt individuals. Last, research has almost exclusively been conducted in contexts where speaking five or more languages is highly unusual, and therefore characteristic of elective learners who are highly motivated and have high language aptitude. Consequently, existing studies on the neurobiology of polyglots may conflate language aptitude and multilingual experience. This is problematic, given that language aptitude can independently predict language-related neural organisation. The present study addresses these limitations by taking advantage of the highly multilingual Swiss context, where circumstantial multilingualism is common. This enables the dissociation of aptitude from experience across a heterogeneous sample (N=121, knowledge of 1 to 50 languages). Participants completed an fMRI localizer involving listening to intact and degraded speech in their first language and behavioural testing of multilingualism (measured continuously via entropy) and language aptitude (phonological perception and production, grammatical sensitivity, and rote learning). Aptitude and multilingualism were weakly correlated (r=0.2), with language aptitude skills explaining only 3.8% of the variance in multilingualism, confirming their relative independence. Whole-brain analyses revealed largely dissociable neural signatures for the two constructs. Higher multilingualism was associated with increased recruitment of regions predominantly outside perisylvian regions, including left precuneus and cerebellum during intact speech, and right angular/occipital, inferior temporal and hippocampal regions during linguistic processing (intact > degraded contrast). This reflects increased engagement of a broad, high-effort system during story listening in people with higher linguistic repertoires. However, during degraded speech processing, more multilingual individuals showed greater activity within traditional language regions (bilateral IFG), suggesting an attempt at higher-level, speech-like decoding of the ambiguous input. By contrast, higher language aptitude was primarily associated with reduced activation within core language regions (bilateral STG, left IFG, and supramarginal gyrus) during intact speech and the intact>degraded contrast, consistent with the neural efficiency hypothesis (e.g., highly skilled learners use fewer neural resources compared to moderately skilled ones). During degraded speech listening, higher language aptitude was associated with increased right STG activation, suggesting a more bottom-up, phonological approach to novel auditory input. Categorical group comparisons (polyglots vs. controls) revealed only a single significant cerebellar cluster (left Crus I), demonstrating the superior sensitivity of continuous versus binary approaches. These results suggest that the neural efficiency signature previously attributed to polyglotism may instead be associated with high language aptitude.
Topic Areas: Multilingualism, Speech Perception