In this chapter, we report on the effects of language learning in adults beyond the language system. We discuss the hypothesis that knowing and practicing multiple languages has an effect on cognition, in particular on executive functions, and the hypothesis that in the bilingual brain, both languages are always active. Current hypotheses on developed cognitive control abilities in bilingual speakers is presented. The final part of the chapter is dedicated to recent research on the protective effects of bilingualism for aging and its contribution to recovery from bilingual aphasia due to brain trauma.

This chapter analyzes how languages are acquired in multilingual contexts and focuses on the development of phonological competence, morphosyntactic skills, and vocabulary. We discuss the differences and similarities that monolingual and bilingual children may show in language development, as well as possible advantages and disadvantages related to bilingualism. We explain that simultaneous exposure to two (or more) languages does not cause confusion or developmental delays, as is often feared by caregivers. We demonstrate that simultaneous bilinguals generally reach language milestones at the same age as monolinguals.

Being bilingual is a common experience for many people. In this chapter we define what is bilingualism according to the most recent research evidence in linguistics and neurolinguistics. A general overview of the different stages of bilingualism across the lifespan and the terminology are presented together with preliminary insight on the properties and capacities of the bilingual brain. Findings reported in the chapter include the role of minority languages, such as local and regional languages spoken by small communities, and their crucial role for sustaining bilingualism globally.

In the final chapter we elaborate on how families and society can support bilingualism, starting from the observation that it is not sufficient to expose a child to two languages in order to attain native-like proficiency in both. In fact, supporting individuals’ development and maintenance of two languages requires important precautions. We discuss the role of linguistic input, from both quantitative and the qualitative points of view, and the importance of formal education in both languages for complete language development, including biliteracy. Moreover, we consider the importance of family and societal attitudes towards bilingualism, emphasizing that all languages should be appraised by the community, regardless of their prestige. We conclude by emphasizing that it is paramount that social policies disseminate correct information about bilingualism and encourage the maintenance of all languages in all of their components.

In this chapter, we focus on language development in individuals suffering from language and cognitive disorders. One of the major concerns of families and caregivers of individuals with these disorders is that exposure to more than one language may cause further difficulties, slow down, or hinder linguistic and cognitive development. Scientific research, however, shows that this is an unmotivated prejudice, and that bilingualism does not provide negative effects, but rather, can offer benefits. We explore the interaction between bilingualism and language disorders, discussing in particular developmental language disorders, developmental dyslexia, autism spectrum disorders, hearing loss, Down syndrome, and aphasia.

This chapter discusses data on the effects of bilingualism for the brain and presents neurobiological models of languages in the brain. We first report on overall changes in brain structure among bilingual speakers, such as the plasticity and adaptation of specific areas of the cortex and other neuroanatomical. The second part of the chapter covers neuroimaging studies and is organized by language modules, including phonology, morphology, syntax, and semantics. The studies reported in this chapter are developing rapidly and are elaborating a better definition of the neural properties of the bilingual brain.