The Zone of Proximal Development

The Zone of Proximal Development (ZPD) is the cognitive space between what a learner can do independently and what is still beyond their reach — the middle zone where a task cannot be completed alone but can be completed with appropriate support. Introduced by Lev Vygotsky in *Mind in Society*, the ZPD is the region where new capability is actually built; tasks below it produce no encoding gain, and tasks above it can't be completed even with support. Session design that places its target outcome inside the ZPD is what converts effort into skill transfer.