# Meaningful Differences identifies the word gap

By [Bryce Edwards](/content/author/bryceedwards/index.html)• May 3, 2018

In the landmark study published in their book [**Meaningful Differences in the Everyday Experience of Young American Children**](http://products.brookespublishing.com/Meaningful-Differences-in-the-Everyday-Experience-of-Young-American-Children-P14.aspx), Betty Hart & Todd Risley recorded parent-child spoken interactions in 42 families. They discovered that some children heard 30 million fewer words by their fourth birthdays than others—and that this “word gap” has long-term effects on later child outcomes. Meaningful Differences has had a huge impact in the twenty years since Brookes published it, prompting followup studies on the word gap and major projects like the _Thirty Million Words®_ Initiative.