Yes, knowledge base is essential, and strongly related to the ideas
of apprenticeship, expertise, etc. and the process of change.
There seem to me to be some general features to look at that intersect,
but are not reduced to, knowledge base. Working memory capacity increases,
allowing (but not requiring!) mental juxtaposition of more complex
aspects/dimensions of a problem. There also appears to be, in some societies
at least, a "turning on thinking" that people call metacognition, which
is sort of a higher order way of theorizing about experience. And all is
wrapped in/constituted in activities of some sort or another; we have some
idea of some classes of those activities (schooling being one).
mike