Understanding ZPD
Internalization is the internal reconstruction of an external operation (Mayer, 2008). "The process of moving from the intermental to the intramental domain takes place through internalization, or, as some translate the Russian original, interiorization (Kozulin, 1990 p. 116). According to Kozulin (1990, p.116), "the essential element in the formation of higher mental functions is the process of internalization." After children have gone through the ZPD and has learned to use their language as tools. They use these tools, their internal speech, to navigate through their culture and environment. In the Wells text he gives the example of dancing. A person learning how to dance looks to others around him on the dance floor and imitates their dancing moves. A person doesn't copy the dance moves exactly per se but takes what he can and adds his/her own twist.
Read more about this topic: Zpd