There is a need for robust evidence about which educational interventions work in preschool to foster children's cognitive and socio-emotional learning (SEL) outcomes. Lab-based individually randomized experiments can develop and refine such interventions, and field-based randomized experiments (e.g., cluster randomized trials) evaluate their…

Points out how the theories advanced during the 1930s by Russian psychologist L. S. Vygotsky can provide insights to western educational psychologists as they seek to understand child development and, particularly, as they devise ways of working with socially disadvantaged and mentally retarded children. (DB)