During 1978–1985, the field increasingly treated play as the central conduit for early learning, with a strong emphasis on social and cognitive development through play. Research highlighted transitions from solitary to more group and dramatic play, and connected classroom processes—such as fostering prosocial behavior—to shifts in curricula that prioritize social-emotional skills. Longitudinal evaluations and program-structure studies suggested preschool experiences yield lasting, though context-dependent, effects on achievement and behavior, underscoring the importance of program quality and environmental design.