Your main job as a presenter is to ensure that throughout your presentation, you and everyone in the audience remain on the same page, even the same wavelength, every step of the way. If your slides contain more information that it takes the average listener more than 10 seconds to comprehend, you can't possibly make this happen. People process information at different rates; faster processors will take a shorter time and the slower processors will take longer. Before you know it, you've got an audience working at three to five different wavelengths at the same time.

Then to make things worse, most presenters start talking, explaining the slide, at usually about the 5 second mark, and thus add one more thought-path, one more wavelength, to the whole process.

The Bell Curve

Think about it. If the amount of time it takes the average reader to ingest the info on the screen is 30 seconds, then a classic bell curve will tell you that 20% of the audience is going to read it all in 20 seconds, and 20% will take 40 seconds. Another aggregate 20 will fall into the 10 to 60 second range, and before we calculate it all, we know that we have the group broken down into at least five groups of perception time-lines. Now, let's screw it all up and throw you into the soup, and you begin talking at some new, arbitrary point. To whom are you speaking?

Chance tells us you're speaking to the largest group; let's say the 40% who read at an average pace. That leaves 60%, a landslide in political terms, either way ahead or way behind the bullet point upon which he begins to expound.

Actually, it gets worse! You see, as much as a you might be totally in love with the design of a slide you may have spent hours composing, audiences rarely find your stuff as captivating. Because the presentation is important to you, it's easy to believe that everyone will be engrossed in the action on the screen and thus giving the event their entire attention.

But tell us: have you ever sat through a colleague's presentation and found yourself thinking about something other than the material he was sweating blood to deliver? Perhaps your plans for the upcoming weekend? The safety of your children? Whether you can let that bill slide this month?

No audience member, no matter how captivating you might believe you are, ever, ever, ever gives a presenter 100% of her attention. Human minds don't work that way. Long before Windows, we were multi-taskers.

As lives become more complicated, and work cuts into personal time, the line between work and personal become blurred, and we compartmentalize less. Although it's difficult to attach hard numbers here, it's reasonable to assume that at best our audiences are tuning in to us -and us alone- more than 75% of the time.

So even if we're directly communicating with 40% of the group, given our (at best) 75% maximum attention factor, we have no more than 30% of the audience in our camp. The rest are either struggling to catch up, or consider themselves so advanced that their minds begin to wander to unrelated topics, such as their children, the weekend, their bills; they become non-participants in the process.

Taking it to the Limit

So what does this tell us? Of course, there is only one truly viable solution, and that is to limit, by all means possible, the amount of information that is released with each click of your mouse.

First of all, the less time it takes the audience to discern the new information, the sooner they'll get back to you and start to listen to what you really mean to ?say? on the slide.

Secondly, the less time it takes the average people to figure out for themselves what's going on, the less the width of the bell curve.

Third, and most important, is this: if your slides are designed correctly and consists of nothing but graphics and talking points, or headline-style phrases, the audience will soon realize that they are not being shown enough information to figure things out for themselves. They will conclude that the only way they can hope to be the first to know is to turn their attention quickly to you, and have it spoon fed to them. And this is exactly where you want them to be!

If you put everything you want them to know up on the screen, and if you spell it out longhand, you are training them to look to the screen for their information. Humans recognize patterns quickly, and as soon as the screen becomes the pattern, that's where they'll go. Problem is, they'll be reading one thing while you're speaking about something else!

The rule of thumb from all this? Make sure that with each passing image, it never takes longer than 10 seconds for the audience to ?clear the slide?. By clearing the slide we mean removing the curiosity. Have no more than 10 seconds of material - bullet point, graphic, chart, etc. - appear at one time.