From a socio-cultural perspective, language offers a means for children to communicate with and learn from others through interaction: language is the medium through which young children are provided cognitive, social, and emotional support in interactions with caregivers, siblings, and peers; and children characterized as dual language learners (DLLs) have in common that they receive this developmental support in two different languages. However, due to variations in socioeconomic factors, ethnic/immigration background, and language socialization practices, DLLs display considerable variability in their first- and second-language proficiency (McCabe, Tamis-LeMonda, Bornstein, Cates, Golinkoff, Guerra, Hirsh-Pasek, Hoff, Kuchirko, Melzi, Mendelsohn, Páez & Song, 2013).