Meaningful Differences in the

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 House’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 opportunity, children from low-income homes remain well behind their more economically advantaged peers years later in school. Each month, they recorded one full hour of every word spoken at home between parent and child in 42 families, categorized as professional, working class, or welfare families. Two and a half years of coding and analyzing every utterance in 1,318 transcripts followed. By age 3, the recorded spoken vocabularies of the children from the professional families were larger than those of the parents in the welfare families. Between professional and welfare parents, there was a difference of almost 300 words spoken per hour. Extrapolating this verbal interaction to four years, a child in a professional family would accumulate experience with almost 45 million words, while an average child in a welfare family would hear just 13 million—coining the phrase the 30 million word gap.

The implications of this painstaking study are staggering: Hart and Risley's follow-up studies at age 9 show that the large differences in children's language experience were tightly linked to large differences in child outcomes. As the authors note in their preface to the 2002 printing of Meaningful Differences, "the most important aspect to evaluate in child care settings for very young children is the amount of talk actually going on, moment by moment, between children and their caregivers." By giving children positive interactions and experiences with adults who take the time to teach vocabulary, oral language concepts, and emergent literacy concepts, children should have a better chance to succeed at school and in the workplace.

Learn more about how parent and children's language interactions affect learning to talk in Hart & Risley's companion book The Social World of Children Learning to Talk.

Betty Hart, Ph.D., began her career in the early 1960s at the Institute for Child Development at the University of Washington, where she participated in the original demonstrations of the power of learning principles in influencing young children. With Montrose Wolf and Todd Risley, she introduced the basic procedures of adult attention and time-out now routinely taught and used in teaching and parenting. She also helped introduce the procedures for shaping speech and language widely used in special education. In 1965, she and Todd Risley began more than 35 years of collaborative work at the University of Kansas, when they established preschool intervention programs in poverty neighborhoods in Kansas City. Their study of what children actually do and say in day care and preschool and their publications on incidental teaching from the empirical base for contemporary child-centered teaching practices in preschool and special education. Dr. Hart was Professor Emeritus of Human Development at The University of Kansas, and Senior Scientist at the Schiefelbusch Institute for Life Span Studies at The University of Kansas. She remained focused on the language development of preschool children.

Todd R. Risley, Ph.D., began his career in the early 1960s at the Institute for Child Development at the University of Washington, where he participated in the original demonstrations of the power of learning principles in influencing young children. With Montrose Wolf and Betty Hart, he introduced the basic procedures of adult attention and time-out now routinely taught and used in teaching and parenting. He also helped introduce the procedures for shaping speech and language widely used in special education. In 1965, Hart and Risley began more than 35 years of collaborative work at the University of Kansas, when they established preschool intervention programs in poverty neighborhoods in Kansas City. Their study of what children actually do and say in day care and preschool and their publications on incidental teaching from the empirical base for contemporary child-centered teaching practices in preschool and special education. Before his death in 2007, Dr. Risley was Professor Emeritus of Psychology at the University of Alaska and Senior Scientist at the Schiefelbusch Institute for Life Span Studies at The University of Kansas. He served on many national boards and commissions, as Editor of the Journal of Applied Behavior Analysis, as President of the Association for Advancement of Behavior Therapy and of the behavioral division of the American Psychological Association, and as Alaska's Director of Mental Health and Developmental Disabilities.