The simple answer is that presentations are intrinsically a sensory experience, primarily seeing and hearing. And a clever presenter can also incorporate the other senses as well.
But do you really need to understand how the brain processes the information the eye sees or the ear hears? After all, you don’t need to understand how a computer processes the information from a keyboard to use it effectively. While this may be true, you do have to have some understanding of how the keyboard works otherwise you’d end of with a mess of letters that made no sense.
The same is true of understanding how our senses work. You don’t really need to know that the neural circuitry of the retina transforms a fluctuating pattern of light into a pattern of neural activity in retinal ganglion cells, which is then transmitted along the optic nerve to the brain . But it’s extremely helpful to know that we don’t “see” images that move very fast or very slow.
If you read the report from my previous post, Seeing, Hearing and Smelling the World, you would know that we are attracted to nothing as much as change. And that applies to all the senses. We organize our world into patterns in order to easily filter out unnecessary information and quickly recognize when something changes. In our primal minds, change represents both danger and opportunity. These were the tools necessary in an eat or be eaten environment. Even today these are still the tools that allow us to avoid car crashes or identify food that’s safe to eat. Whether we want to admit it or not, from a sensory perspective, we all have attention deficit disorder (ADD.) Anything that doesn’t change every 5 seconds is largely ignored.
I recently attended The Presentation Summit and overheard some patrons who had attended a session on presenting webinars. They were complaining that the session presenter had said they needed to make a change every XX seconds. They interpreted this as needing multiple slides for every minute of the presentation/webinar. I think they missed the point. Webinars are the ultimate ADD environment. Your attendees will be checking their email, typing documents or working on a plethora of other activities while you are presenting and you’ll never know it. You are competing for their attention. If you do not provide rapid stimulation (change) in your presentation, you will lose your audience pretty quickly. This doesn’t mean a different slide, the change can be as simple as raising the volume of your voice or a simple highlight on a slide. You just need some small change that tells their senses “Pay Attention! Something has changed.” But beware of repetition which by definition is a sort of unchange. While a repeating animation might hold our attention for longer than 5 seconds, we’ll quickly learn to ignore it.
By knowing and understanding these concepts you can take advantage of opportunities that most magicians have known about for centuries. There is truth in the old adage, “the hand is quicker than the eye.” It isn’t actually, but our brains don’t process everything the eye sees.
Most people have difficulty registering identifying details about an object that moves faster than 36 degrees per second. Since your visual field is around 180 degrees, anything that crosses in and out of your visual field in less than five seconds starts to blur. And because the cells in your eyes get tired of stimulation after more than two or three seconds, anything that doesn’t move significantly in that amount of time will be perceived as stationary. 
This is what allows us to make films. They are simply a series of still images strung together and presented rapidly enough that our brains perceive motion. You can use this knowledge to add interest as well as dynamic and subtle changes to your presentations.
In my quirky presentation called the Mouseover Magic Show, I used these concepts to do something that the software (Microsoft PowerPoint) is very limited in supporting. If you download the presentation and run it, you can move your pointer over any mouse and they will appear to change. In actuality, it’s jumping to a whole new slide, but because the background doesn’t change, we only recognize the change of the mouse. We aren’t aware the entire slide has changed. I’ve created this simple slideshow specifically to illustrate this technique for creating mouseovers.
If I’m the PowerPoint Magician, my friend Julie Terberg is the PowerPoint Illusionist. She applies the concepts of visual motion in an elegant and sometimes surprising way that’s sure to hold an audience’s interest.
PowerPoint 2010 has some new transitions that are specifically designed to exploit this quirk in our visual sense. They’re called Dynamic Content Transitions. They provide movement of the content on the slide without moving the background. You can achieve pretty spectacular effects using just the transitions. I discussed these transitions on the Indezine Blog and posted a downloadable timeline template that uses these transitions. You must run the template in the desktop version of PowerPoint to see the transitions properly.
Every presentation should have an element of magic to it. Every presentation should have its prestige (a mysterious quality of enchantment) moment. Nancy Duarte calls this the STAR moment in her new book, Resonate. It’s the moment where you’ve connected with the audience on such a primal, emotional or spiritual level that they feel compelled to pay your message forward again and again. Understanding the psychology of the senses will help you create this moment.
Finally, if you downloaded and ran the Mouseover Magic Show you might have noticed the card trick. The how and why that works is a discussion for another day.
 Visual Perception: physiology, psychology, & ecology By Vicki Bruce, Patrick R. Green, Mark A. Georgeson
 How Fast Can the Eye See? | eHow.com