Lev Vygotsky 1896-1934
"Zone of proximal development" (ZPD)
Low level of ZPD is the skill available to a child working without guidance (independently). The higher level is the potential of the child. The potential usually requires the assistance of an instructor. Vygotsky believed that learning precedes development. The child needs to be stretched beyond their limit. Comprehension and full integration will come later.
See "Activity theory".