The grip of grammar on meaning uncertainty: cross-linguistic evidence, neural correlates, and clinical relevance
Organizations: Grammar and Cognition Lab, Department of Translation & Language Sciences, Universitat Pompeu Fabra, Barcelona, Spain. · School of Foreign Studies, Guangzhou University, Guangzhou, China. · Department of Neurology Sant Pau Memory Unit, Hospital de la Santa Creu i Sant Pau Biomedical Research Institute Sant Pau, Barcelona, Spain. · Frontotemporal Disorders Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, USA. · Ace Alzheimer Center Barcelona, Universitat Internacional de Catalunya, C/Gran Via de Carles III, 85 bis, 08028 Barcelona, Spain. · Networking Research Center on Neurodegenerative Diseases (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain. · Department of Language Science and Technology, Saarland University, Saarbrücken, Germany. · Department of Operation and Management, Zhuhai People's Hospital (The Affiliated Hospital of Beijing Institute of Technology, Zhuhai Clinical Medical College of Jinan University), Zhuhai, China. · Department of Statistics, Zhuhai People's Hospital (The Affiliated Hospital of Beijing Institute of Technology, Zhuhai Clinical Medical College of Jinan University), Zhuhai, China. · Faculty of Medicine, Macau University of Science and Technology, Macau, China. · Guangdong Provincial Key Laboratory of Tumor Interventional Diagnosis and Treatment, Department of Radiology, Zhuhai People's Hospital (The Affiliated Hospital of Beijing Institute of Technology, Zhuhai Clinical Medical College of Jinan University), Zhuhai, China. · CIDCL, Escuela de Fonoaudiología, Universidad de Valparaíso, Valparaíso, Chile. · Department of Psychiatry and Psychotherapy, University of Marburg, Marburg, Germany · Marburg University, School of Medicine, Department of Psychiatry and Psychotherapy, Marburg, Germany · Department of Adult Psychiatry and Psychotherapy, University of Zurich, Zurich, Switzerland. · Neuroscience Center Zurich, University of Zurich and ETH Zurich, Zurich, Switzerland. · Center for Clinical Neuroscience and Cognition and Department of Psychiatry, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands. · Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, Quebec, Canada. · Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. · Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. · Institut Català de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
Abstract
Isolated word meanings are inherently uncertain. This uncertainty reduces when they are combined and anchored in context. We propose that grammar compresses meaning uncertainty cross-linguistically, which is reflected in brain and selectively disrupted in disorders. Compression was operationalized as the relative difference between non-contextual surprisal estimated from lexical frequency, and contextual surprisal from grammar-sensitive models. In narratives from 20 languages, contextual surprisal reduced frequency-based surprisal. This reduction closely tracked the surprisal cost of reversing word order, and scaled with richer, non-redundant lexis as organized by more complex but optimal dependency structure. During fMRI, surprisal and its reduction explained BOLD activity for comprehension and production in overlapping but distinct regions. Uncertainty reduction was significantly attenuated in aphasia, dementia, and schizophrenia, but remained intact where primary deficit is not language. These findings position uncertainty reduction via grammar as a foundational concept that illuminates principles, brain basis, and disruptions of language.