The next decade of research on the effectiveness of early intervention.

The effectiveness of early intervention programs for children with developmental disabilities and for children at biologic risk was reviewed and analyzed. A general pattern indicating important effects of early intervention programs was noted, with effect sizes averaging between one-half and three-quarters of a standard deviation. The ability of early intervention programs to minimize declines in development was identified as a significant outcome. The effects of specific program features--age of start and family involvement--were selected for more detailed examination, and the moderating influence of the levels of severity of children's disabilities was also analyzed. Future directions for improving the effectiveness of early intervention include using the emerging knowledge of biobehavioral and child development research, as well as enhancing children's social competence.