Titone and Tiv's Systems Theory of Bilingualism aims to “urge cognitive scientists and neuroscientists to better embrace sociolinguistic and sociocultural experiences as part of their theoretical and empirical purview”. No stronger case for such a framework can be found than in studies of developmental aspects of bilingualism. In fact, inclusion of sociocultural variation has been a common feature of many studies of dual language learning for some time, especially in studies of pre-school and early-school-age learners (see Genesee, 2019, for a review). Young dual language learners – neonates, infants and toddlers, exposed to more than one language – begin life as virtual tabula rasa and are capable of learning any language with facility. As a result, their language acquisition is necessarily tied to the sociocultural parameters of the learning environments they are exposed to. Moreover, as Titone and Tiv emphasize, the immediate and ultimate purpose of language learning is communication. Thus, young dual language learners must be attuned to and acquire the sociocultural constraints and norms for communicating effectively in more than one language. While sociocultural variation is important for understanding language acquisition even among monolingual children living in relatively homogeneous monocultural environments, sociocultural variation is inherent and, indeed, enhanced in the learning environments of children acquiring more than one language insofar as each language is intimately linked with different socio-cultural parameters. Sociocultural variation can be important for understanding bilingualism in yet another way. In studies of the neuro-cognitive consequences of bilingualism, it has been reported that there is a more pronounced association between dual language exposure and activation of certain brain areas among adolescent bilinguals from relatively low SES backgrounds than bilinguals from relatively high SES backgrounds (Brito & Noble, 2018). Inclusion of sociocultural variation in research on the effects of bilingualism can reveal a more nuanced view than emerges if such variation is not considered.

This study investigates the development of wh-questions in French in a group of bilingual French-Dutch children. Fifteen children (aged 4 to 8, mean age 6;03, first exposure to French under age 4 for most of the children) participated in an elicited production task. Their results were compared to those of 4-year-old and 6-year-old monolingual children from a previous study. In order to examine possible influence from Dutch, two main hypotheses with contrasting predictions are proposed: structural overlap and derivational complexity. The results show that the bilingual children exhibited the same developmental course for wh-questions as their monolingual peers. The majority of responses involved wh-fronting without inversion, whereas wh-fronting with inversion, the only possible structure in Dutch, was not frequent. Therefore, the results do not provide clear evidence for influence from Dutch. Instead, they confirm that derivational complexity constrains the development of wh-questions in French.

This study investigated the role of age-of-acquisition in determining whether young bilingual children show a pattern of L2/nonnative English, precocious BE acquisition, or whether they show the L1/native English pattern of synchronous acquisition of BE and inflectional morphology. Two groups of children with age-of-acquisition before or after 4;0 and equivalent exposure to L2 English were given production and grammaticality-judgement tasks. The children in both age-of-acquisition groups showed the precocious BE pattern, regardless of L1 background and on both tasks. We conclude that, for this aspect of morphosyntax, bilingual children who begin to learn English after age 3;0 are best characterized as child L2 rather than bilingual L1 learners.

This paper contributes to current investigations of the nature of babbling in infants raised bilingually by analyzing the babbling of a child raised in a Spanish–English environment. Examination of syllable structure shows the expected preponderance of open syllables in both language contexts while other phenomena point to important differences dependent on language context. While some of the differences relate to general features of the input languages, others coincide with individual features of the parents’ input. These results offer some evidence of distinct babbling according to language context and suggest a possible influence of the type of input.

Previous studies have showed that at age 3;0, monolingual children acquiring rhythmically different languages display distinct rhythmic patterns while the speech rhythm patterns of the languages of bilingual children are more similar. It is unclear whether the same observations can be found for younger children, at 2;6. This study compared five Cantonese–English simultaneous bilingual children with five monolingual children in each language using both rhythmic metrics and qualitative data on syllable structure complexity and lexical stress. Results show that while the speech rhythms of monolingual children are different at 2;6, the rhythmic patterns of bilingual children are less distinct.

This study investigates the acquisition of speech rhythm by Cantonese–English bilingual children and their age-matched monolingual peers. Languages can be classified in terms of rhythmic characteristics that define English as stress-timed and Cantonese as syllable-timed. Few studies have examined the concurrent acquisition of rhythmically different languages in bilingual children. This study uses data of six Cantonese–English bilingual children around age 3;0 and compares them with six monolingual children in each language using recently developed acoustic rhythmic metrics on consonantal, vocalic and syllabic intervals. Qualitative data on syllable structure complexity and vowel quality are also included. Results on syllable duration show that monolingual children display distinct rhythmic patterns while the differences between the two languages of the bilingual children are less distinct. Bilingual English has less durational variability than monolingual English. Bilingual children have a distinct phonological developmental trajectory from monolingual children, which is manifested in acquisition delay and is influenced by language dominance. This shows that the two phonologies interact at the prosodic level.

Chinese noun classifiers are an obligatory category associated with nouns. Studies have shown that achieving a full understanding and good mastery of Chinese noun classifiers is difficult for both young and adult L2 learners. This study examines the learning strategies used by 30 Swedish adults for a period of two months. Their learning results are compared to 30 bilingual children's production of Chinese noun classifiers. The adult learners exhibit a normal top–down learning fashion, in which they fail to acquire the complex semantic and cognitive meanings embedded in the classifiers. The children, on the other hand, apply cognitive strategies with a bottom–up approach. The adults’ learning of classifiers lags surprisingly far behind their general level of Chinese proficiency. This study can be used as a reference for future studies on the conceptual and cognitive aspects of Chinese language acquisition by speakers whose native languages are not classifier languages.