'The Cognitive Neuroscience of Bilingualism'  By John W. Schwieter and Julia Festman, A Book Review By Brenda Walker

31st Mar 2025

    This volume is part of the Cambridge Fundamentals of Neuroscience in Psychology Series which seeks to provide ideal primers for students and other readers interested in the various challenges of neuroscience. Those keen to explore how bilingualism affects changes in the brain will appreciate, not only how the book is set out, but also the breadth of the material Schwieter and Festman include in each of the eight chapters.   

    From the start the authors acknowledge that ongoing brain research continues to surprise as new information emerges regarding brain anatomy and neural functions of both single and network regions.  Yet despite world-wide research in different disciplines, results in the field of bilingualism have proved inconclusive. Reasons for this are explored and light shed on related problems in this fascinating, multidisciplinary study, covering, alongside neuroscience, the relevant fields of psycholinguistics, and cognitive psychology. Although there are many books on bilingualism, this volume claims to be the first to discuss the many psychological and theoretical issues ‘with respect to language processing and representation, while providing insight into the “reality” of the bilingual brain.’   

     This book certainly presents as  a primer due to every chapter beginning with a section on ‘Learning Objectives’ followed by an ‘Introduction’, numerous sections on the topic of that particular chapter, a ‘Summary’, and finally, ‘Review Questions’ with ‘Further Reading’. There are many Figures, Models, and invaluable Tables listed with the Contents, together with a two-page colour plate section. In addition, there are sixty-three pages of references, a three-page index, and in the Acknowledgements section, a web site is given for a radio interview that took place in April, 2022 with the CNN Chief Medical Correspondent, Dr. Sanjay Gupta entitled “How language lights up the brain”.  In this interview, Dr. Gupta discusses many aspects of this book with Professor Schwieter seeking answers to such questions as: ‘If learning a language is so difficult, how we did it as children? Are our adult brains cut out for learning new languages? Are there potential health benefits of being bilingual?’ Joining in the discussion, the cognitive scientist, Lera Boroditsky explains the possibility of language having the power to shape the way we think and see the world.  

    The primary aim of this volume is to examine how the neurological organization and functioning of the brain supports bilingual language acquisition, and to explore what is actually meant by the term ‘bilingualism’;  a term often used in conversation without consideration to levels of fluency, competence, or proficiency in one or more of the four linguistic skills.  In the search for a conclusive definition the reader is led through a maze of theoretical and empirical issues.  To date, research has looked at some but not all aspects of classification, thus creating an imbalance in comparative results. Omitting just one variable similar to those listed below could change the outcome: the age of acquisition; circumstances and manner of acquisition; linguistic environment; relevant proficiency; sociocultural environment; language fluency; literacy; learning environment; culture; exposure to two languages in early childhood, or many other possible areas of grouping.  

     In such specific research, the focus may be linguistic or psychological, depending on the disciplines involved and each will have their own approach with theories and models based on empirical data. Examples given are: linguists, who investigate the linguistic aspects of the ‘product’; sociologists, who focus on conditions of language in society and culture, educationalists who observe interaction in the classroom , and psychologists who are more concerned with processes in the mind that relate to language activity.  In addition there are psycholinguists, neurolinguists, neurologists and cognitive neuroscientists, all with their own specific interests working towards the same goal, yet finishing with different definitions of bilingualism.  

     As around sixty percent of the world’s population are bilingual, the authors conclude that a multilingual mind/brain is more likely to be the default rather than an irregularity. Highly qualified and experienced in the fields of language learning, linguistics, cognition and multilingualism, Schwieter and Festman describe in great detail the various aspects of language including its multiple dimensions.  Their study considers the bilingual’s mental imagery for concepts and words, while examining prominent models that explain not only how words are ‘mapped onto concepts’, but also the degree of conceptual overlap between languages. Among other dimensions discussed are categories, characteristics, and the representational aspects of subcomponents: sound; words, morphology; semantics and syntax. These areas, regarding structure and organisation, are later divided into seven more types of linguistic information: phonological, orthographic, semantic, morphological, syntactic, pragmatic, and discourse, all tabulated with referenced explanations. 

     To move research forward in this complex world of linguistics, ‘a window into the brain’ is deemed a necessity, and Chapter 1. produces many methodological considerations which take into account possible techniques to either assess brain anatomy, detect current brain activity, or record electromagnetic changes in the brain related to language processing.  By analysing the work of other theorists on areas such as word recognition, representation, production, distribution and comprehension, the authors explore an historical viewpoint of key language areas and lateralisation in the study of bilinguals since the 1880s, along with anecdotal brain functions regarding the two hemispheres and other questionable outdated theories.  Each research study’s contribution is analysed and assessed, but the authors give particular attention to a study by MacDonald, (2013) on Production, Distribution and Comprehension (PCD) when describing how language production shapes language form and comprehension:  

‘The PCD hypothesis holds that, during language production, memory and planning demands strongly affect the form of speakers’ utterances.  MacDonald analysed verb modification ambiguities and relative classes and found that production choices influenced these comprehension phenomena.  She argued that sentence comprehension phenomena may be better explained through distributional regularities in language and utterance planning processes as proposed in the PDC, rather than by the comprehension system architecture approach. Therefore, she proposes that research in language comprehension must also be studied alongside production processes. MacDonald suggests that the influence language production has on language form and comprehension may support a mechanistic account of language production that includes covert production processes.’ 

      Brain plasticity is defined as ‘the capacity of the cortex to reorganize its connections as a reaction to perceptual cognitive/or motor skill learning’. (Credit for this definition is given to Buonomano & Merzenich, 1998).The authors then elucidate brain anatomy, with diagrams. Neurons are depicted as the building units of the brain; the importance of synapses, synaptogenesis, axons and dendrites are stressed as is the efficiency of pruning / blooming, the way myelination improves conduction and the role played by white and grey matter.  The reader is also reminded of Donald Hebb’s principle ‘repeated coactivation of neurons changes the strength of connection among them, which leads to faster and easier activation’. – Often taught as:   ‘Neurons that fire together, wire together’, for it has long been suspected that ‘Lifelong learning’ rewires the brain. 

      Later in the volume, the cognitive and neurocognitive effects of bilingualism are compared thus enabling the reader to consider the consequences of learning and using two or more languages; the question being whether or not development and learning are separate concepts or exist on a continuum sharing the same neural mechanisms.   Also considered, when learning and frequently alternating two languages in one mind, is the impact on cognition, brain structure and function. Tables 7.1, 7.2 and 7.3 illustrate the above, moving from behavioural evidence on the general executive control processes to neuroscientific evidence regarding the effects on the brain.  These parameters of bilingualism and their effects are listed in three columns. Listed on the left-hand side in 7.3 is the neuroscience evidence, headed ‘Source in bilingualism:  assumptions, explanations and theories’. ‘Effects on the brain’ is in the central column, while on the right is noted: ‘Example studies and reviews’.  Such lists are an invaluable aid to the student. However, general readers may need to brush up their knowledge of current brain anatomy on a much clearer image than the small black and white version drawn on page 35.     Language learning involves a rich network of memory connections that enhance recall when the brain is accessing multiple entry points in order to retrieve the information from specific situations, images, or emotions.  The various stages and types of memory involved are discussed fully, and detailed within informative Tables depicting the brain’s multiple memory and learning systems. The lists being split into: ‘Dicotomies’, ‘Explicit / Implicit memories’, and ‘Associative areas of the brain’. 

     Bilingual Aphasiology is perhaps an unfamiliar term to many, but the authors elucidate the premorbid factors that influence language impairment together with lesion sites of Aphasia, their clinical manifestations and the process of rehabilitation.  Another area of great interest is the chapter on cross-linguistic effects of bilingualism, their domains and the various factors that can affect transfer. Apparently, there has not been much research on the language spoken by a fluent bilingual person while dreaming; although it has been reported by bilinguals that both languages are used depending on the situation and context.  Language switching and the neural and electro-physiological activity involved is yet other aspect of this well delineated, engrossing volume.  The trajectory of research on switching from one language to another since 2005 is depicted with research details. However, the authors conclude that: ‘the psycholinguistic processes that underpin code-switching appear to be more heterogeneous and complex than previously thought.’ 

     Learning another language is a slow process and Schwieter and Festman are justified in describing this comprehensive resource on bilingualism, language, the brain and behaviour, as not an ‘easy story to tell’.  Nevertheless, despite their accessible prose being woven with references, the authors are to be congratulated in culminating a wealth of research taken from specific disciplines, which have highlighted a variety of perspectives and methods on the relationship between these four important areas. 

      If any older readers find themselves suddenly immersed in a country where they need to learn and use the language, and/or become involved in the job of translating, the good news is, that having developed a new cognitive reserve they may just have distanced themselves from the scourge of dementia.  Bilingualism may be a continuum, but so is brain plasticity.   

Brenda Walker.   March 2025