I don't understand this theory that states there are only three kinds of mental loads:The theory is that there are basically three different kinds of  demands or loads that you can make on a person: Cognitive (thinking  and remembering), Visual, and Motor.Source, Posted on February 17, 2011 by Susan Weinschenk.What about things like listening to someone speak? Or if someone's learning to play a musical instrument and is trying to hit the right note. Is this only in the context of interaction design. 
What is meant by this theory that there are only 3 possible kinds of cognitive loads?
cognitive psychology;cognitive neuroscience