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.

The vast majority of children grow up in bilingual or multilingual households, but the extent to which they develop advanced linguistic abilities and even literacy in all their languages depends on many factors. These include age of acquisition of the two languages, the amount of exposure to and use of the languages daily and in specific or diverse contexts, and the status of the languages in the society, including access to schooling. For some simultaneous and sequential bilingual children, one or more of their languages is a minority language not widely spoken outside the home and with little cultural, educational, social and political status. In some other circumstances, the language or languages can be minoritized, available beyond the home but considered lower in status in the society. In this chapter, I discuss research on the development of the minority/heritage language(s) in simultaneous and sequential bilingual and multilingual children, with specific focus on the school-age period. I focus on how bilingual balance and language shift in these children and in many cases lead to language attrition and incomplete acquisition of morphosyntactic aspects of the minority language.