"Meaningful Differences in the Everyday Experience of Young American Children" is the story of the landmark research study that uncovered the widely cited "word gap" between children from low-income homes and their more economically advantaged peers. This groundbreaking research has spurred hundreds of studies and programs, including the White Housea s "Bridging the Word Gap" campaign and "Too Small to Fail," a joint initiative of the Bill, Hillary, and Chelsea Clinton foundation.

Betty Hart and Todd Risley wanted to know why, despite best efforts in preschool programs to equalize...