Talking to children matters: Early language experience strengthens processing and builds vocabulary

Abstract

Infants differ substantially in their rates of language growth, and slower growth predicts later academic difficulties. This study explored how the amount of speech to infants in Spanish-speaking families low in socioeconomic status (SES) influenced the development of children's skill in real-time language processing and vocabulary learning. All-day recordings of parent-infant interactions at home revealed striking variability among families in how much speech caregivers addressed to their child. Infants who experienced more child-directed speech became more efficient in processing familiar words in real time and had larger expressive vocabularies by 24 months, although speech simply overheard by the child was unrelated to vocabulary outcomes. Mediation analyses showed that the effect of child-directed speech on expressive vocabulary was explained by infants’ language-processing efficiency, suggesting that richer language experience strengthens processing skills that facilitate language growth.