Too much multimedia in learning content is analogous to too much Flash on websites. Not in terms of what purpose the multimedia serves, but in the sense of visual/auditory overload.
This Dutch site is my current favourite example of too much Flash, if it’s a real shopping site. Perhaps it’s a parody of one; there’s nothing clickable on the page. As you scroll, images fall and rise; sometimes you scroll up and the page goes down by itself; animations begin at random; and so on.
It reminds me of the Overload issue. Let’s be concise and look at... not best practices in multimedia, but examples of multimedia overload in learning material.
1. It’s relevant but distracting
Every designer tries to use only relevant audio-visual material, but ask yourself: This graphic is relevant, but maybe it’s distracting? Overly colourful images can be distracting. “Cute” animations can be distracting.
2. It augments but it overloads
A universal guiding principle is that a multimedia element should add value to the rest of the material. Even so, it can overwhelm.
An example I can think of is text that explains, in simple terms, how something works... with a process diagram on the same page. This is overload because it confuses: “Should I follow the words, or should I look at the diagram and figure it out? Should I match the words with the diagram?”
It’s a similar case if the explanation is a process animation were accompanied by narration.
3. It’s balanced but it steals focus
Sometimes, the mere placement of an element can cause distraction. Imagine a three-minute video snippet of a lecture, with a well-designed text box appearing on the other side of the screen. The learner would shift his eyes to the text box. Distraction.
Even using the same elements, it would be better if the text box were to appear at a place on the screen near the speaker.
4. It serves the purpose but steals attention
I’m reminded of audio-visual course/chapter transitions. They make for a quick mental break while indicating there’s something new ahead. But if it lasts too long, your learner might think a lot of things? “Is it stuck there?” “Is the program over?” Problem is, he might still be thinking about that when the new topic begins.
5. It adds visual relief but too much of it
Visual relief is often a good thing—perhaps almost always; opinions will differ. Suppose you have only text and images to work with. Each text screen with a different image might be distracting, as opposed to a group of screens with the same image, followed by another group with a different image.