A Longitudinal Investigation of the Role of Quantity and Quality of Child-Directed Speech in Vocabulary Development

Quantity and quality of caregiver input was examined longitudinally in a sample of 50 parentchild dyads to determine which aspects of input contribute most to childrens vocabulary skill across early development. Measures of input gleaned from parentchild interactions at child ages 18, 30, and 42 months were examined in relation to childrens vocabulary skill on a standardized measure 1 year later (e.g., 30, 42, and 54 months). Results show that controlling for socioeconomic status, input quantity, and childrens previous vocabulary skill; using a diverse and sophisticated vocabulary with toddlers; and using decontextualized language (e.g., narrative) with preschoolers explains additional variation in later vocabulary ability. The differential effects of various aspects of the communicative environment at several points in early vocabulary development are discussed.