This chapter aims to unravel the contribution of the neuroscience of reading to the study of literacy development across languages and writing systems. The development of early literacy can be adversely impacted by neurodevelopmental disorders and socioeconomic disparities that have lasting effects on child and adolescent cognition. The goal of this chapter is to address the continuum of literacy development in two critical stages, birth-to-six and six-to-ten years old, and their respective language and brain milestones: the hardwired brain networks for speech, and the adaptation of brain regions for reading. The discussion attempts to disambiguate neurodevelopmental disorders and socioeconomic factors that influence early literacy, and the associated effects on brain function and structure. It is concluded that there is emerging evidence for a near-universal brain system that develops with learning to read across writing systems and the chapter addresses the dynamic relations among brain networks for reading, speech and writing across the two age spans. It is also claimed that the neuroscience of reading has the potential to inform prediction of reading achievement, identification of risk for reading difficulties, and possibly, choice of intervention and of the age ranges that are more amenable to treatment.

In this introductory chapter, we examine the worldwide distribution of literacy, its development with schooling, and the sources of individual variation in literacy outcomes. Various perspectives on global variation are discussed while also aiming for a common framework to describe literacy development that recognizes demographic boundaries in the world, on the one hand, and its global variation as a function of bio-ecological markers on the other hand. In this introduction, we draw attention to the wealth of recent research on variations in literacy development that arise across regions and that reflect the multiple interrelated influences of individual, home, school, and societal factors. Furthermore, observations on the neurobiological and ecological markers related to global literacy are discussed. These include the role of writing systems, genetics, brain foundations, self-regulation, and sociocultural, contextual, teacher, and parental factors in global literacy development. An explanatory framework is also provided showing that literacy development involves gaining reading fluency and spelling to facilitate reading comprehension and writing, that it builds on language, and that child characteristics and home- and school-support factors combine to influence individual variation, within an indirectly influential sociopolitical context.

In this final chapter, a wide-angle perspective is provided on the major issues that arise when one thinks globally about literacy. Despite many important differences across the globe, literacy development suggests some general patterns that reflect nearly universal phases and shared operating principles. Although the “development” of literacy begins early through natural processes of language development and conceptual development, it is school experiences, explicitly designed to teach reading, that we expect to ensure the achievement of literacy. Each classroom within a school is its own literacy ecosystem, with one or more teachers, students, literacy curriculum materials, assesments, and regulated interactions. The classroom itself is embedded within other systems – the school, the community, the larger school administrative units, and local, regional, and national government control agents. A Global Literacy Framework is presented, showing that literacy development is embedded in language development and can be predicted by (a) system factors, referring to variations in the linguistic and writing systems, (b) child factors, associated with the neurobiological foundation of children’s learning capacity, and (c) support factors, associated with processes in the home and at school. All these influences exist within a sociopolitical context that exerts influence broadly across the system.

In the history of human evolution, reading and writing skills were developed about 5,400 years ago (Dehaene, 2009), which is fairly late in the context of the 350,000–150,000 years of history of human speech (Perreault & Mathew, 2012). In terms of ontogeny, the acquisition of reading also follows that of speech over the course of the child’s early years. Nonetheless, reading has become one of the most important cognitive functions for daily life and reading difficulties can severely limit an individual’s ability to thrive in the modern world (Calfee, 1982; Rawson, 1978). Across languages and cultures, approximately 5–20 percent of the population (depending on definitional criteria) is affected by developmental dyslexia (DD), a specific reading impairment presents in the absence of other cognitive impairments (S. E. Shaywitz & Shaywitz, 2003).

In this final chapter, we provide our view on some of the main conclusions that can be drawn from the research on developmental dyslexia across languages. The overarching questions concern how our understanding of reading disability benefits from considering a broad array of languages. If there is a universal biological basis of developmental dyslexia, there should be shared observations on reading disability across languages and writing systems. Or, so one might expect. It is possible, however, that observations of differences in the manifestations of dyslexia – whether subtyping within a language (e.g., phonological vs surface dyslexia) or comparisons across languages (e.g., alphabetic vs morphosyllabic) – reflect some unitary cause or combinations of multiple causes.

Reading involves decoding written language in order to understand it. In learning to read, children implicitly learn how their writing system encodes their spoken language and how they can decode printed words into spoken words to derive meaning (see Verhoeven & Perfetti, 2017). However, many children around the world encounter problems learning to read, fail to develop fluent decoding, and are thus diagnosed as dyslexic.

A large body of research supports the conclusion that a phonological deficit underlies most developmental dyslexia. Much of the existing evidence, however, is based on studies of children learning to read in English. It is important to note that English has an opaque orthography that creates challenges beyond those facing children who read more transparent orthographies. In recent years, the research base for developmental dyslexia has broadened across languages, allowing the question of differences and similarities across languages and writing systems to receive attention.