Lev Vygotsky
The zone of proximal development
Look at the second line
Thought and Language
Two people at the same level today may end up far apart. Which measure the difference shows up in.
What actually happened?
Vygotsky pointed out that ability has two lines: what a person can do alone, and what they can do with help; between them lies the zone of proximal development. His example is two children who stop at the same point solving a problem alone, and then, given a small hint, one goes a long way further and the other doesn't. Identical actual level, completely different zone — and it's the zone that decides what they can learn next. Against the orthodoxy of his day he argued that teaching should run ahead of development, not wait for it.
Assess by the response to a hint
Independent performance alone underestimates the difference. What actually predicts is how far someone moves once given a little help — that shows where they can grow next. For managing people and for teaching children this is the same measure.
Two reports produce about the same today. Give the same pointer: one advances at once, one doesn't. Invest in the first.
Pitch it just above where they are
Hard enough to need help, not so hard that help doesn't get it done. Below that is repetition; above it is discouragement. It's the same location that deliberate practice calls the edge of the comfort zone, named differently.
Teaching equations to a child who has just learned addition is wasted. So is only ever doing addition.
First between people, then inside one
He held that higher thinking happens in interaction first and is internalised after — a child is questioned by adults before learning to question themselves. That is why discussing, retelling and teaching someone else beat reading silently.
Explain the thing you can't grasp to another person. You're borrowing the structure you haven't internalised.
How do I use it today?
Where you are: teaching someone or teaching yourself, and unsure where to set the difficulty.
Ask first: can they do this alone? Can they do it with one hint? The stretch between is what to practise.
Where it goes wrong: reading 'run ahead of development' as the further ahead the better. Too far ahead only discourages.
Lines to keep
Between what you can do alone and with help lies the zone.
Teaching should run ahead of development.
Higher thinking happens between people before it happens inside one.