Vygotsky!

Using language is a SOCIAL activity. This makes a lot of sense. People want, need and seek out social interaction at all ages. We need to connect with others and language is probably the best way to do this.
One could argue that these concepts are common sense analyzed and labeled with what seem like rather big words. I have been taught by and have observed seasoned teachers who don't know what any of these words mean and who have never read Vygotsky yet use these principles every day in their teaching.
Working with students in the Zone of Proximal Development seems like a constructionist approach.
Overall good ideas and I think Vygotsky trumps Piaget.