Piaget was an 'individual constructivist,' that is, for Piaget the mental development of a child was internal, self directed and individualist. Piaget remarked,
"in order for a child to understand something, he must construct it himself, he must re-invent it. Every time we teach a child something, we keep him from inventing it himself."
Vygotski on the other hand was a 'social constructivist' that is. for Vygotski a child learns by interacting socially by means of speech and other means with the people around him. This process is known as 'scaffolding' and the adults with whom the child comes into contact play a very important role in mediating its acquisition of knowledge.