Readers of this blog will know I’m not a big fan of slideware for speakers. This position is so heretical for most of the business world that I often end up working with executives to simplify and otherwise improve their slides because they can’t live without at least something on the screen behind them.

You can’t win ‘em all. Now, honesty demands that I confess that I’ve run across a new study that suggests one very good reason and use for slideware. I’ll get to that in a minute. But first, a few words on the proper use of PowerPoint-like slide programs, whether Keynote or Prezi, or something else.

Here is the low-down on slideware. The usual business slide is covered with words, and what most people connect to is pictures – preferably pictures of people or perhaps kittens. What’s more, they learn best from simple pictures. So move them emotionally with pictures of faces (or kittens or puppies), and connect your key concepts visually to triangles, circles, squares, and the like.

Don’t get fancy. It’s simply not necessary, and it doesn’t promote learning. In addition to pictures, you can use graphic illustrations, tables and charts, and the like, for help with numbers, but keep in mind that simpler is usually better. For example, pie charts are good slide material; tables that have the same information expressed as raw numbers are most definitely not. You want to find a visual image to represent the number. Especially if it’s a big number you’re trying to talk about – we humans have trouble with numbers over 3 digits in length.

You should only be attempting to express one idea in each slide.  (My old friend Ed Tufte argues otherwise, and I have huge respect for his take on illustrative maps and diagrams, but I do believe they’re best suited to books and other places where you have a longer, closer interaction with them, rather than slides.)

Here’s the best way to think about visuals, especially PowerPoint. It’s the way that writers of Broadway musicals think about the songs. They put in a song when the emotion of the moment demands something more than words. That’s why the stars are always breaking into song when they realize that they love each other, for example. You should use PowerPoint just as sparingly. Don’t think of it as wallpaper that’s always there behind you, but a discrete moment in your talk when you turn to an illustration because it’s too difficult to put the idea into mere words.

If you apply this stringent test to your use of PowerPoint, you’ll find that you use it much more sparingly and effectively. You can go to black in between these song-worthy moments.

When you do use PowerPoint or one of its rivals, a few simple further rules can help avoid the usual mistakes. I actually like title slides that go up before you speak—at conferences where there will be a series of speakers, for example. It helps the audience keep track of what’s coming up. But I don’t like PowerPoint wallpaper while you’re speaking. It’s distracting for the audience and raises the awful risk that the audience will find it more interesting than you. Why test the ice?

So use PowerPoint for illustrations. Pictures. Graphs. Pie charts. That sort of thing. If you must use it for words, keep the words to three lines or fewer. Yes, that means no more than three bullets, and the bullets should never exceed a line. Otherwise they’re not bullets, they’re poorly worded sentences, and a tip-off that you’re indulging in a speaker outline — the real sin in public speaking slide use.

Make your headline, if you need one, a complete sentence. Here’s why. Rather than saying, “Implications of Cost-Cutting on the Department,” or some such, a full sentence will force you to say something like “Cost-cutting will mean the elimination of needed services.” Do you see how the second statement is more interesting than the first? It tells you the thought, whereas the first headline just tells you that a thought is coming.

PowerPoint users have at their disposal a plethora of fonts, clip art, and bells and whistles that let items zoom in from the left or right, or other such glittery effects. Eschew them. They are merely an apology for real thought. Stick to a full sentence headline, or a key number, and an image, if you must use words. Better: just a picture. Best: no slides at all.

Remember, a presentation is an act of persuasion. You’re most persuasive when it’s just you. If you ask someone to marry you, will you use slides?

Now, what was that new study on how to boost comprehension? Oh, yeah. It found that having people stare at a natural scene – or a picture of one – for 40 seconds boosts concentration and reduces mental errors. And that is in fact the first bona fide study of slideware improving retention I’ve actually seen. So perhaps your title slide should have your name over a background of a natural scene, and you should show it for at least 40 seconds before you begin.

That’s a use of slideware I could get behind.