Size matters: Early vocabulary as a predictor of language and literacy competence

ABSTRACT This paper investigated the predictive ability of expressive vocabulary size and lexical composition at age 2 on later language and literacy skills from ages 3 through 11. Multivariate analysis of covariance was performed to compare 16 language and literacy outcomes between children with large expressive vocabulary size at 24 months ( N = 1,073) and those with smaller expressive vocabulary size. Comparisons between large and small verb size groups as a measure of lexical composition were also conducted. Our findings indicate that, after controlling for gender, birth order, ethnicity and socioeconomic status, total vocabulary size at age 2 can significantly predict subsequent language and literacy achievement up to fifth grade. Moreover, vocabulary size is a better predictor of later language ability than lexical composition.