Medinaa, TN, Snedekerc, J, Trueswella, J, & Gleitmana, G. (2011). How words can and cannot be learned by observation. Proceedings of the National Academy of Sciences, 108(22), 9014-9019.
"If language experiences are not rich, then where is your interest to retain them?" says Janice H. Im of Zero to Three: the National Center for Infants, Toddlers and Families. A new study from University of Pennsylvania and Harvard University suggests that understanding basic words may come from a flash of initial insight more than repetition. The study's findings suggest that children build concrete vocabulary by interacting with a complex, rich learning environment, not just repeated exposure to words in isolation.