This study focuses on the relationship between the amount of exposure to Basque and Spanish languages, and the expressive vocabulary of a group of 88 children (aged 16-30 months) living in the Basque Autonomous Community in Spain. The expressive vocabulary of these children in both languages and their relative amount of exposure were estimated using parental reports obtained with the standardised Basque and Iberian Spanish versions of the Communicative Development Inventory II (CDI II). A high degree of individual variability was found in the amount of exposure (more/less balanced relative input), as well as in vocabulary size (in one or both languages) of these early simultaneous bilingual children, even among those within the same age category (measured in months). Statistical analyses were performed after introducing age of participants as a covariate, and the results revealed a) a strong effect of the relative amount of exposure on the expressive vocabulary size in Basque, but no effect on the Spanish vocabulary size, and b) no effect on the conceptual vocabulary of the children. These findings are consistent with the claim that the amount of exposure affects language specific vocabulary size, more than conceptual vocabulary. The divergent results in the two languages indicate that the majority versus minority status of the language can influence lexical development in toddlers.
Ezeizabarrena et al. (Wed,) studied this question.