Individual Differences in Lexical Processing at 18 Months Predict Vocabulary Growth in Typically Developing and Late-Talking Toddlers


  • This research was supported by grants from the National Institutes of Health (HD42235 and DC008838). We are grateful to the children and parents who participated in this study. Special thanks to Nereyda Hurtado, Ana Luz Portillo, Poornima Bhat, Christine Potter, Amber MacMillan, Adriana Weisleder, Christina Branom, Rebecca Wedel, Renate Zangl, and the staff of the Center for Infant Studies at Stanford University.

concerning this article should be addressed to Anne Fernald, Department of Psychology, Stanford University, Stanford, CA 94305. Electronic mail may be sent to


Using online measures of familiar word recognition in the looking-while-listening procedure, this prospective longitudinal study revealed robust links between processing efficiency and vocabulary growth from 18 to 30 months in children classified as typically developing (= 46) and as “late talkers” (= 36) at 18 months. Those late talkers who were more efficient in word recognition at 18 months were also more likely to “bloom,” showing more accelerated vocabulary growth over the following year, compared with late talkers less efficient in early speech processing. Such findings support the emerging view that early differences in processing efficiency evident in infancy have cascading consequences for later learning and may be continuous with individual differences in language proficiency observed in older children and adults.