ABSTRACT
Children vary widely in the rate and breadth of vocabulary acquisition across early childhood. This chapter reviews relevant literature on the nature of individual differences in children's early word learning, including issues relevant to measuring that learning. It proves several child-factors and other proximal environmental factors that account for some of this variation. More recent advances in methodology and technology have allowed researchers to sensitively measure very early language comprehension and production. Word learning is an area of language that shows large variability in both size and rate of acquisition. The speech that children are exposed to during the early childhood period is consistently strongly related to the rate and breadth of vocabulary acquisition. The chapter summarizes the research to date on the predictors and consequences of the quantity and quality of parents' child-directed speech for children's word learning. The communicative environments that children are immersed in during early childhood help shape their vocabulary development.
