# Instructional design/Reducing cognitive load in multimedia instruction/Cognitive Theory of MML Continued

Remember the 5 cognitive processes -- selecting words, selecting images, organizing words, organizing images, and integrating? That is known as Essential Processing and is one part of the total cognitive demand of the learner. The arrows in the model represent this cognitive processing. The arrow from words to eyes represent printed words being seen by the eyes; the arrow from words to ears represent spoken words being heard by the ears; and the arrow from pictures to eyes represent pictures or images being seen by the eyes. The selecting arrows represent the learner’s attention to some of the auditory or visual sensations coming in from the ears or eyes. Arrows labeled organizing represent the learner's construction of a coherent verbal or a pictorial representation based, in part, from the incoming words and images. This is known as Representational Holding.
Finally, the arrow labeled integrating represents the merging of the verbal model, the pictorial model, and relevant prior knowledge. The selecting and organizing processes may be guided partially by prior knowledge activated by the learner. Another type of cognitive demand is Incidental Processing. Incidental processing are elements of the instruction that while interesting, are not essential to meaningful learning. Although not essential, their presence also requires processing and thus contributes to total cognitive demand. Cognitive Demand is a combination of all three demands. We can think of it as an equation:
As depicted in the model, all of those arrows can add up to a lot of processing demand. For the learner, this only becomes a problem if the demand exceeds the learner cognitive capacity. Let's take a look at some principals of capacity.
       1. The capacity for physically presenting words and pictures is virtually unlimited
       2. The capacity for storing knowledge in long-term memory is virtually unlimited.
       3. The capacity for mentally holding and manipulating words and images in working memory is limited.
Given principal number 3, we now know that the working memory columns (shaded blue) in the model, are subject to the limited-capacity assumption. These demands can create drags on learner's processing capacity and can easily turn into Cognitive Overload. Now comes the dilemma. How do we as instructional designers create an opportunity for “meaningful learning” which requires copious amounts of cognition, when the learner capacity is so limited? This means we have to be attentive to learner cognitive load while still creating space for meaningful learning to take place. We can also think of “Cognitive Overload” as an equation.
In short, introduce too many concepts in too many ways and overload is almost guaranteed. So what do we do about it? We can try to reduce cognitive load by redistributing essential processing, reducing incidental processing, and/or reducing representational holding. Sounds like a neat trick you say, but how?
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