How to juggle languages: Verbal short-term memory as a key predictor of code-switching in dual language learning 3- to 6-year-olds

This study investigates how dual language learning preschooler’s code-switching relates to their linguistic and cognitive strengths and challenges. Utilizing a cross-sectional approach, we examined preschool-aged children in Switzerland and Germany acquiring a societal language (German or French) together with a heritage language (Italian or Turkish). We hypothesized that age-related maturation in verbal short-term memory, alongside language abilities and inhibitory control, shapes children’s code-switching both within (intrasententially) and between sentences (intersententially). Parent-based code-switching reports of 106 children aged three to six years were incorporated into a generalized mixed model analysis, which also included data from linguistically parallelized tests administering societal and heritage language skills together with linguistically unbiased cognitive assessments. Findings indicate that as children age, their intrasentential switches to the heritage language decrease, while their intrasentential switches to the societal language slightly increase. Verbal short-term memory, improving with age, seems to facilitate intrasentential switching to the societal language. Moreover, strong inhibitory control helps avoid unintended intrasentential switches to the societal language. Switching intersententially is not affected by age or cognition. Irrespective of intra- or intersentential switches, switching towards the societal and heritage language reflects children’s linguistic strengths and difficulties, with a noticeable preference for switching into the societal majority language, even when language proficiencies are controlled. Using a comprehensive research design, this study offers valuable insights into children’s dual language development. Code-switching is portrayed as a complex behavior significantly shaped by the development of verbal short-term memory, alongside strengths and challenges in linguistic skills and inhibitory control, as well as further influenced by the broader language environment within the society.