Here are the constituents of we might call modern multimedia theory, and their founders (... and for which we can thank Richard E. Meyer for lacing together in his wonderful book, Multimedia Theory)
Dual Coding Theory, Pavio
Working Memory, Baddeley
Cogntive Load, Sweller
Generative Theory, Wittrock
For all of these, perhaps the overriding component is this last, the generative notion of the mind (mind defined, for now, as simply as "what the brain does") as an actor, building meanings, testing them against evidence and knitting them into what has already been stored away in long-term memory.
The old model of the brain was a passive one. It fit well into the industrial model of schooling, with boxes and bells and students sorted by age. Sitting in those classrooms, we took in knowledge when it was placed in front of us, and our labor was that of mere retention for regurgitation at testing time. The emphasis was on all the social and spatial arrangements around the student, about teaching and not about learning.
This is important, I think, because we still see that old passive brain model reflected in schooling and in much of "adult education" and industrial training today. "Sit 'n git" still rules in too many places when we really should know better.
An active brain model is better suited to these times when machines are taking over for teachers in much of the non-school teaching establishment (....oh, the machines are coming to the schools alright, but we will probably hold out there for decades.) The question for MM designers and educational technologists is what ought we be doing with these machines to make the best use of what we now know about human learning?
If the active brain is the foundation, dual coding theory is the first story of the emergent model. There are two channels for us humans; one for processing visual information, the other, auditory. Scholars have gathered a considerable body of knowledge about the interactions of these two channels and the media objects they encounter.
Oddly, a third channel, the haptic/kinesthetic, does not seem to have made much of a stir in mainstream, academic discourse yet, even though a century of experience with Montessori's constructivist ideas seems to be well-supported by findings on the value of movement, physical media, collaboration and discovery, not just for children but life-long learners. The interface and game designers are way ahead of the academicians, though, at least on the haptic dimension. (A good topic for a later inquiry.)
Working memory and cognitive load are closely interlinked. More on that next time.