The federal Early Head Start (EHS) program began in 1995, and a randomized trial was conducted to evaluate the efficacy of 17 EHS programs. In all, 3,001 low-income families (35% African American, 24% Hispanic, and 37% White) with a pregnant women or an infant under the age of 12 months were randomly assigned to a treatment or control group (with…

Preschoolers' questions may play an important role in cognitive development. When children encounter a problem with their current knowledge state (a gap in their knowledge, some ambiguity they do not know how to resolve, some inconsistency they have detected), asking a question allows them to get targeted information exactly when they need it.…

This commentary on the study reported in this monograph focuses on three topics raised by the study: (1) social systems, or individuals in the context of institutions; (2) the study of development through the use of disabled populations as experiments in human growth; and (3) the ability of intervention programs to manipulate development. (BC)