The pace of vocabulary growth helps predict later vocabulary skill

Abstract

Children vary widely in the rate at which they acquire words--some start slow and speed up, others start fast and continue at a steady pace. Do early developmental variations of this sort help predict vocabulary skill just prior to kindergarten entry? This longitudinal study starts by examining important predictors (socioeconomic status [SES], parent input, child gesture) of vocabulary growth between 14 and 46 months (n = 62) and then uses growth estimates to predict children's vocabulary at 54 months. Velocity and acceleration in vocabulary development at 30 months predicted later vocabulary, particularly for children from low-SES backgrounds. Understanding the pace of early vocabulary growth thus improves our ability to predict school readiness and may help identify children at risk for starting behind.

Figure 1

Plots of empirical growth trajectories (a), predicted growth trajectories from cubic model (b), and average vocabulary growth from cubic model (c) (n=62). Figure 1: Empirical growth (b) Predicted cubic growth (c) Average growth (predicted)

Figure 2

Effect of SES and child gesture on cumulative vocabulary growth, holding parent input constant (at its mean). High SES and High Gesture are plotted at the 75^th percentile Low SES and Low Gesture are plotted at the 25^th percentile