With Labour Day past, we back in the season of slide shows -- million of them daily in both academia and business. For over a decade now, slide shows have become an accepted prop for public speaking, regardless of whether they are useful or well-designed, and the trend shows no sign of slowing. You can, of course, just acquiesce and accept that as soon as you click to the first slide, most of your audience will sigh deeply and sit back low in their chairs. But, if you really want to make slide shows work for you, you'll think before opening up the Impress wizard.

The most famous criticism of slide shows is Edward Tufte's essay, "The Cognitive Style of PowerPoint." His viewpoint is brutally (and comically) succinct: Slide shows are a one-way form of communication, and "usually weaken verbal and spatial reasoning, and almost always corrupt statistical analysis." In his equally famous poster, he likens a slide show to an old Soviet May Day rally, with a dictator haranguing squares of troops. Almost equally well known is the Gettysburg PowerPoint Presentation, which strips Lincoln's famous speech of its rhetorical power and replaces it with a set of banal bullet points.

There are, of course, situations where the natural tendencies of slide shows are useful. For instance, if you are assembling a trade fair demo that is going to loop continuously, you're in a situation where one way communication is inevitable.

Similarly, if you're an assistant professor teaching an introductory course to 600 students, you're not going to get much interaction no matter what you do. Probably, too, you have to convey a lot of information in a short time, so you don't especially want interruptions. Nor are you likely to be doing more than introducing concepts, so the risk of over-simplifying them will usually be small.

In other situations, though, whether a slide show is useful is less easy to decide. The trick in making the decision is to observe when the natural tendencies of slide shows are suitable for what you are presenting, and when they are not. That in itself is a radical idea in an era when slide shows are given as a matter of course. But, if a slide show doesn't suit your need, you are far more likely to communicate successfully by not using one than by building one just to meet expectations.

Deciding when to use Impress by purpose

One of the simplest ways to decide whether you should be using a slide show is to ask

yourself if any of the following situations will apply:

• You are lecturing and don't expect much interaction with your audience for whatever reason.
• You are giving brief, general instructions before moving on to other ways of interacting with your audience.
• You have illustrations -- pictures, charts, or diagrams -- that will help your audience understand what you are talking about.
• Your information falls naturally into small, fixed categories without over-simplification.
• Your slide show is only one way in which you will interact with your audience -- and, preferably, will be relatively brief.
• Your audience is older, deeply interested in the subject, or already expert in the subject -- that is, if it is likely to have a longer attention span.
• Your presentation is 15 minutes or less.

Conversely, if any of the following situations apply, you should probably reconsider the whole idea of a slide show:

• Interaction with your audience is an important part of your presentation.
• You need to interact with members of your audience individually.
• Language -- either rhetoric, as in a poem, or deep analysis of meaning, such as in a legal document -- is important to your presentation.
• Your information is complex or abstract, so that it doesn't fit naturally onto slides with 5-8 short bullet points on them.
• The slide show is your only presentation method.
• Your audience is younger, mildly interested, or being introduced to the subject -- that is, more likely to become restless during a presentation.
• Your presentation is longer than 15 minutes.

In both lists, you should probably not base your decision on a single factor. However, if you think about each of the points on the list, you shouldn't take long to realize whether a slide show will help your presentation or drag it down.

Guarding against one-way communication

Once you have decided to prepare a slide show, your challenges are just beginning. Except in cases in which you actually want one-way communication of simple ideas, you need to struggle against the limitations of slide show as a medium all through your preparation.

The simplest way to avoid these limitations is to avoid developing a presentation that is a summary of everything you have to say. Not only will your audience pay more attention to the slide shows than to you, but, unless you are very careful, you are likely to start reading the slides -- in other words, to stop reacting to your audience and breaking your ideas up into the bullet points on the slides.

When that happens, you might as well just send your presentation along and not bother to appear in person. You certainly won't be adding anything to the slide show by being its animated mouthpiece.

Instead of making your slide show a summary of your talk, use Impress at what it's good for: that is, presenting graphics for your audience. Write the notes for your presentation, then mark the places where a graphic might help your audience's understanding (it might help to ask yourself where you might put a graphic if you were writing an essay rather than a slide show). Do the same for any keywords or citations that your audience might want to know how to spell or to look up later for themselves. Add a title page, and possibly a summary of key points at the end, and that is all your slide show is likely to need.

Admittedly, preparing a slide show of this kind will feel awkward -- even wrong -- if you are used to presentations that are basically your notes. What everyone else is doing has a way of quickly seeming the only correct way to do things, regardless of whether it is effective or not. But if you persevere, you will find that this style of slide show dramatically changes your relation with your audience during the presentation.

Without a summary of your notes on the screen, both you and your audience will spend less time staring at the screen and more time looking at each other. As a result, the audience is more likely to stay attentive, and will probably ask more questions. Chances are, too, that you will notice the audience reaction and know when to depart from your notes to explain or emphasize more, or to invite more questions.

Of course, for inexperienced users, the kind of slide show I am suggesting is not as safe as the stereotypical summary. It forces you to focus more on your audience, and denies you the comfort of clinging to your slides. But it is far more likely to succeed in conveying information -- which is, after all, what you are supposed to be doing. If you try it, I think you'll be surprised at how much more effective your presentations will become.