 Because different cultures stress different social interactions, this challenged Piaget's theory that the hierarchy of learning development had to develop in succession.Vygotsky introduced the term Zone of proximal development as an overall task a child would have to develop that would be too difficult to develop alone.Also, the so-called neo-Piagetian theories of cognitive development maintained that Piaget's theory does not do justice either to the underlying mechanisms of information processing that explain transition from stage to stage or individual differences in cognitive development.