Early child measures outpredict input measures of preschool language skills in U.S. English learners

Prior work finds that some elements of language input or skills during infancy and toddlerhood predict later language skills. Here we ask if combining these two sources of information about early language development improves predictions of language outcomes, using a longitudinal dataset that captures early language input and abilities over the first five years in a sample of 44 American English-learning children. While several early language skills significantly predicted later language skills (Spearman’s rho=0.44-0.63, p<.05), most infant input measures did not. Notably, the most robust predictor of preschool language was parent-reported productive vocabulary at 1.5 years. This suggests that early language assessments (e.g., parental-reported vocabulary) can be reliable measures of language skills with high predictive value for longer-term language outcomes.