A commonly cited number that visual presentation and PowerPoint trainers use is the 5-Second Rule (if you have A.D.D. it may be the 3-Second Rule). It simply states that your audience should “get” your slide in that short amount of time. You can liken this to the experience of trying to read a billboard as you zoom by at highway speeds — you need to get it quickly and then return to the task of driving or risk disaster.
Why so urgent a need to absorb a visual? It is simply this: there are countless ways for your audience to be distracted from you, the presenter; having overly complex slides is just adding fuel to that fire. I see the 5-Second Rule as more of a guidepost. Of course there is just cause for more complex slides that will hold the viewer’s attention. But the longer they are engaged in the task of deciphering your slide the greater the chance they will not completely return their focus to you.
There is also a point of over-saturation as well, only so much material can be absorbed from a slide. Adding more detail does not guarantee it will be understood.
Keep it simple, please — add complexity at your own peril.
