Language mixing in young multilingual children and its correlates: a systematic review

• We reviewed studies on social, linguistic and cognitive factors and language mixing. • The social context plays an important role in children’s language mixing. • Children mix more in their less proficient and non-dominant language. • Studies on cognitive factors are scarce and inconclusive. • Research can benefit from a greater focus on interrelations between various factors. Globally, numerous children are raised in multilingual environments, mixing different languages in their everyday communication. This systematic review on children’s language mixing aimed to a) identify which social, linguistic, and cognitive factors have been studied in relation to language mixing, and b) examine associations and interrelations between these factors and (different types of) language mixing, focusing on typical language development, naturalistic settings and early childhood (2–6 years). Synthesis of 80 relevant articles from the initially identified 4,239 records showed that most studies focused on social factors ( n = 69), followed by linguistic ( n = 46), and cognitive factors ( n = 6). Key findings include that children are more likely to mix in their minority language, in the language they receive lower input in, in informal settings, and in multilingual contexts. They may also mix more in the language in which they are less proficient, and in their non-dominant language. Results on other factors remain inconclusive (e.g., interlocutor mixing, discourse strategies) or scarce (e.g., language attitudes, language distance, cognitive factors). Moreover, results for some factors (e.g., language proficiency) varied for the different mixing types. Future research should place greater emphasis on the interrelations between different factors, as several theories on child development and language mixing highlight that the social environment and child-internal factors likely interact. Moreover, there is a need for more diverse samples, especially regarding multilingual communities in the Global South, along with research on the role of executive functions in early childhood language mixing using comparable measures.