Lev Vygotski's scaffolding and his Zone of Proximal development

His theory of the "Zone of Proximal Development" (ZPD), "Proximal" simply means "next". He observed that when children were tested on tasks on their own, they rarely did as well as when they were working in collaboration with an adult. It was by no means always the case that the adult was teaching them how to perform the task, but that the process of engagement with the adult enabled them to refine their thinking or their performance to make it more effective. For him, the development of language and articulation of ideas was central to learning and development. The common-sense idea which fits most closely with this model is that of "stretching" learners.
Full development of the ZPD depends upon full social interaction. The range of skill that can be developed with adult guidance or peer collaboration exceeds what can be attained alone. Vygotsky's theory was an attempt to explain consciousness as the end product of socialization. For example, in the learning of language, our first utterances with peers or adults are for the purpose of communication but once mastered they become internalized and allow "inner speech".

Principles:

1. Cognitive development is limited to a certain range at any given age.
2. Full cognitive development requires social interaction.

Bibliography:
http://www.instructionaldesign.org/theories/social-development.html
http://www.learningandteaching.info/learning/constructivism.htm#Vygotsky