The landmark 1988 study by Hayes and Ahrens is frequently cited by literacy organizations. The point is that reading books aloud to children provides exposure to a wider range of words than simply talking to children.  Even adult level prime-time television shows do not use as wide a variety of rare words as children’s books. Other studies have found that the vocabulary of college student conversations do not contain the breadth of words in children’s books.

The Hillsdale Library encourages parents to read to their young children. You make the time. We have the books. And the books are free!

Hayes, D. P. and Ahrens, M. G. 1988. “Vocabulary Simplification for Children: A Case of ‘Motherese.'” Journal of Child Language 15: 395-410.

http://www.reachoutandread.org/impact/importance.aspx

http://www.education.com/reference/article/fact-file-language-development/