Comparing apples to manzanas and oranges to naranjas: A new measure of English‐Spanish vocabulary for dual language learners.

The valid assessment of vocabulary development in dual‐language‐learning infants is critical to developmental science. We developed the Dual Language Learners English‐Spanish (DLL‐ES) Inventories to measure vocabularies of U.S. English‐Spanish DLLs. The inventories provide translation equivalents for all Spanish and English items on Communicative Development Inventory (CDI) short forms; extended inventories based on CDI long forms; and Spanish language‐variety options. Item‐Response Theory analyses applied to Wordbank and Web‐CDI data (n = 2603, 12–18 months; n = 6722, 16–36 months; half female; 1% Asian, 3% Black, 2% Hispanic, 30% White, 64% unknown) showed near‐perfect associations between DLL‐ES and CDI long‐form scores. Interviews with 10 Hispanic mothers of 18‐ to 24‐month‐olds (2 White, 1 Black, 7 multi‐racial; 6 female) provide a proof of concept for the value of the DLL‐ES for assessing the vocabularies of DLLs. [ABSTRACT FROM AUTHOR]