Weighing up predictors of early vocabulary development: The role of babble, pointing and maternal education

McGillion, M. 1 , Herbert, J. 1 , Pine, J. 2 , Keren-Portnoy, T. 3 , Vihman, M. 3 & Matthews, D. 1

1 University of Sheffield
2 University of Liverpool
3 University of York

The transition to conventional language in the second year of life forms a cornerstone of development that social interactions and future academic achievements can build on. Understandably, therefore, researchers have attempted to establish which factors can predict the substantial and persistent individual differences that are observed in early vocabulary development. However, until now, different strands of developmental research have tended to focus on one type of factor or another in isolation, despite calls for a more integrated approach to the study of early word learning (Hall & Waxman, 2004). The present study considered three key predictors of conventional word learning simultaneously: onset of canonical babble, onset of pointing and parental education. We aimed to measure and weigh up these predictors to explore for the first time how they related to one another and to determine which best predicted subsequent word learning. Drawing on an existing longitudinal dataset of naturalistic video-recorded dyadic interaction, we coded for the mother?s level of education, the onset of babble (two stable consonants) and the onset of index finger pointing on a single sample of 46 infants. A parental report, the MacArthur Bates Communicative Development Inventory, was used to measure the infant?s expressive and receptive vocabulary knowledge at 18 months. Babble onset was not related to pointing onset or maternal education. However, infant pointing was moderately correlated with maternal education (r=0.35, p<0.05). Furthermore regression analyses revealed that pointing onset was a significant predictor of receptive vocabulary whereas babble onset was a significant predictor of expressive vocabulary at 18 months. Maternal education was a significant predictor of both vocabulary outcome measures. These findings highlight how pre-linguistic vocal and gestural abilities, while often produced in an integrated fashion early on, are not synchronised and moreover make independent but equal contributions to word learning.