Meaningful Differences establishes a scientifically substantiated link between children's early family experience and their later intellectual growth - a link that exists regardless of a child's race. This compelling story describes the authors' years of research as they search for the roots of intellectual disparity. Hart and Risley examined the daily lives of 1- and 2-year-old children in typical American families. They found staggering contrasts at the extremes of advantage - and within the middle class - in the amount of interaction between parents and children. These differences in the amount of early family experience translate into striking disparities in the children's later vocabulary growth rate, vocabulary use, and IQ test scores - critical measures of an individual's ability to succeed at school and in the workplace. Meaningful Differences, the culmination of Hart and Risley's decades of collaboration, reveals profound effects of environment on development.