Early intervention: why, for whom, how, and at what cost?

When the concept of intervention is applied to human development, the goal is usually to enhance functioning or to prevent some unwanted condition. During the past 20 years, the United States has committed itself to an early intervention position for young children who are socio-economically, educationally, or physically disadvantaged. This article summarizes the knowledge base concerning early educational interventions and to recommend actions concerning public policy and associated research.