We have witnessed a growing number of investigations into the acquisition process in a multilingual context, which has become recognized as an independent field, quantitatively and qualitatively different from second language acquisition. Scholars have started to differentiate between learners/speakers on the basis of the complexity of their linguistic background, with the numer of known languages being an additional variable. A growing body of studies into the acquisition of third language phonology demonstrates an inherent complexity of the field reflected, among others, in multidirectional dynamic cross-linguistic influence. As shown, multilingual learners have at their disposal a broadened phonetic repertoire, a raised level of metalinguistic awareness and enhanced perceptual sensitivity, which may facilitate the learning of subsequent phonological systems. Thus, this chapter aims to compare bilingual and trilingual phonetics and phonology by providing an overview of recent research into both subdomains, identifying their common features and, importantly, their points of departure for L3 phonology, with a view to providing new insights into the acquisition of speech.

Pronunciation teaching is often based on assumptions that learners are monolingual speakers, with the sound system of their native language determining the segmental and suprasegmental difficulties that mark learners’ foreign accents. However, many, if not a majority of speakers of other languages come to pronunciation with more than one language under their command. These bilingual/multilingual speakers are the norm in a globalized world, but how we teach pronunciation rarely accounts for the knowledge and skills these speakers bring to the learning of pronunciation. This chapter describes how the characteristics of bilingual speakers suggest how pronunciation teaching can be reimagined to take into account the range and flexibility of bilingual speakers in using multiple languages. Specifically, we argue that taking a nativeness viewpoint is inconsistent with taking a bilingual viewpoint and calls for pedagogical techniques that build on the kinds of needs bilingual speakers have in pronouncing additional languages.

This chapter reviews research on the phonetic and phonological production patterns of children exposed to two or more languages in early childhood. Much of the research has examined whether bilingual children differ from monolingual children in their production patterns and, when differences have been found, whether such patterns can be explained by language-internal (e.g., the influence of the phonological properties of one language on the other), language-external (e.g., language input or dominance), or other factors (e.g., the developing lexicon). We focus on language-internal influences, also referred to as cross-linguistic interaction, and review models that have been used to account for interaction. Our findings reveal that, while systematic differences between monolingual and bilingual speech exist, the differences are not large and may be explained by multiple factors. The chapter concludes with a discussion of research limitations which include small participant numbers and a predominance of certain language pairs, factors that have hindered attempts to model cross-linguistic interaction.

This chapter examines the acquisition of vowels and consonants in perception and production during typical second language (L2) acquisition by sequential, dominant bilinguals. The acoustic and articulatory studies reviewed serve to illustrate general patterns of L2 segmental learning with a focus on four principal themes, each structured around one or two main research questions: 1) cross-linguistic influence (How does a sequential, dominant bilingual’s first language shape L2 segmental perception and production?); 2) development (Are there universal patterns to L2 segmental speech development? Are certain vocalic and consonantal phenomena acquired more easily?); 3) inter- and intralearner variability (What are the sources of differences in perception and/or production between learners and for the same learner over time and in different communicative contexts?); and 4) training effects (What are the effects of training on learning? How do variables such as task and stimuli type condition effectiveness?).

Heritage language speakers, or heritage speakers in short, are early sequential or simultaneous bilinguals whose home language, generally a diasporic or an indigenous language, differs from the majority language of the society. The goal of this chapter is to provide a comprehensive background of heritage speakers and their sound systems. It includes a literature review on the phonetics and phonology across heritage languages, particularly those of children of immigrants, in various majority language contexts. The chapter first describes heritage speakers and the general characteristics of their language learning experiences and outcomes. It then reviews studies examining heritage speakers’ global accent and factors contributing to perceived heritage accent. It also presents areas of divergence that have been found in the production and perception of heritage language segments and prosody. Lastly, the chapter synthesizes the findings, discussing common patterns observed in heritage language phonetics and phonology, and suggests areas for future research.

Evidence that listeners attend to and track subphonemic phonetic details is indicated by listeners’ ability to reliably connect subphonemic variation and, often, socio-indexical associations in ways that align with the patterns realized in production. Bilinguals are presented with the task not only of associating within-language variation (e.g., social group X is connected to a particular range of phonetic realizations within language Y) but also of attending to how ethnolects and bilingually accented speech index social categories across languages. Having access to multiple languages also gives bilingual speakers a larger repertoire with which to index language- and community-specific social meaning. This chapter outlines the linguistic structures bilinguals may connect across their languages and then presents a specific exemplar model, noting the opportunities within the model’s structure for bilingual dynamics. The heterogeneity of bilingual individuals and speech communities is necessarily addressed, as this dynamic adds to the complexity and intrigue of studying bilingual populations.

The influence of one language on the other when bilinguals speak and write monolingually is an intriguing phenomenon. The author first revisits how interference has been defined over the years by major researchers. He then argues that the definitions proposed were simply too broad, and covered not only interferences but also other contact phenomena such as code-switches and borrowings. The only way to get to the bottom of this problem is to control the language mode bilinguals and language learners are in when they are being observed. In addition, he suggests that we differentiate permanent traces of one language on the other (to be called transfers) from ephemeral intrusions of the other language (these would be interferences). The author continues by describing research conducted with his colleagues on Spanish–French bilinguals in the French-speaking part of Switzerland. The results obtained allowed them to have a better understanding of language restructuring in a first language. In addition, and as a by-product, it gave them a way to differentiate ephemeral intrusions from more permanent traces of the other language. He ends the chapter with a few words on bilinguals’ comprehension of speech containing cross-linguistic influences that comprise both transfers and interferences.

For bilinguals, the use and knowledge of one language affects how they process the other. Various cross-linguistic influences (CLI) can be observed in both language production and comprehension across all domains of linguistics. We start by broadly exploring the concept of transfer, both negative and positive, and forward and reverse. In doing so, we identify various classifications of CLI. Following this, we review key studies on phonological, lexical, morphological, and syntactic transfer along with other types such as discursive, pragmatic, and sociolinguistic. We find that there are a number of factors that can determine the degree to which transfer emerges or whether it happens at all. We then review studies investigating the ability to switch between the two language systems. In doing so, we look at theoretical models that explain what facilitates language switching and what empirical studies tell us about the neural and electrophysiological activity that arises in language switching. Finally, we discuss dreaming and bilingualism and argue that dreaming in an L2, contrary to popular belief, does not necessarily imply fluency in that language.

Chapter 3 explores cross-linguistic influence and various theories thereof in multilingual settings in which more than two languages interact with one another. It is specifically interested in the direction and strength of such influence, contingent on parameters like age of onset, proficiency, L1 and L2 status, linguistic and typological proximity, recency of use, language dominance, as well as various others. It identifies cross-linguistic influence as the more encompassing concept in comparison to the traditional notion of transfer widely used in second language acquisition studies. It also discusses the relationship between cross-linguistic influence and language interdependence, as proposed in education studies. While language interdependence builds on the proficiency-enhancing qualities of multilingualism (qua metalinguistic awareness), cross-linguistic influence can be both facilitative and inhibitory, the latter manifesting itself as interference. Crucially, non-facilitative transfer only arises within a normative system. Moreover, the mechanisms underlying cross-linguistic influence show important parallels to those identified in language contact studies with its focus on contact-induced language change.

Language contact is at its most intense within one and the same individual. This chapter discusses the dynamic and multifaceted phenomenon of individual bilingualism, which emerges when individuals learn to understand multiple language varieties. Individual bilingual language use may contribute to societal processes of language change, language maintenance, and language loss. It is as yet not fully clear how bilingual individuals affect such larger processes, but cross-linguistic influence in comprehension and production, patterns of language choice, and variable levels of proficiency across the lifespan all play a role. These in turn depend on individuals' contexts for learning and using languages throughout the lifespan. The chapter exemplifies some of these on the basis of bilinguals' language biographies (including Frederick the Great's). Language learning histories and opportunities for using each language help explain the large variability in language skills and use among bilinguals. New languages can be learned until well into adulthood. Their number is constrained only by learning opportunities and motivation. Previously learned languages, including languages learned very early in life, can be lost through lack of use and practice. Language attitudes play a large role in all of this.