While at the BUCLD conference this last weekend, I found myself thinking about the cognitive effects of using PowerPoint presentations. If you haven't read Edward Tufte's Cognitive Style of PowerPoint, I highly recommend it. His thesis is that powerpoint is "costly to both content and audience", basically because of the cognitive style that standard default PPT presentations embody: hierarchical path structure for organizing ideas, emphasis on format over content, and low information resolution chief among them.
Many of these negative results -- though not all -- occur because of a "dumb" use of the default templates. What about good powerpoint, that is, powerpoint that isn't forced into the hierarchical path-structure of organization, that doesn't use hideous, low-detail graphs? [Of course, this definition includes other forms of slide presentation, like LaTeX; I'll use the word "slideware" to mean all of these]. What are the cognitive implications of using slideware, as opposed to other types of presentation (transparencies, blackboard, speech)?
Here are my musings, unsubstantiated by any actual research:
I'd bet that the reliance on slideware actually improves the worst talks: whatever its faults, it at least imposes organization of a sort. And it at least gives a hapless audience something to write down and later try to puzzle over, which is harder to do if the talk is a rambling monologue or involves scribbled, messy handwriting on a blackboard.
Perhaps more controversially, I also would guess that slideware improves the best talks - or, at least, that the best talks with slideware can be as good as the best talks using other media. The PowerPoint Gettysburg Address is a funny spoof, but seriously, can you imagine a two-hour long, $23-million-gross movie of someone speaking in front of a blackboard or making a speech? An Inconvenient Truth was a great example of a presentation that was enhanced immeasurably by the well-organized and well-displayed visual content (and, notably, it did not use any templates that I could tell!). In general, because people are such visual learners, it makes sense that a presentation that can incorporate that information in the "right" way will be improved by doing so.
However, I think that for mid-range quality presenters (which most people are) slideware is still problematic. Here are some things I've noticed:
1. Adding slides is so simple and tempting that it's easy to mismanage your time. I've seen too many presentations where the last 10 minutes are spent hastily running through slide after slide, so the audience loses all the content in the disorganized mess the talk has become.
2. Relatedly, slideware creates the tendency to present information faster than it can be absorbed. This is most obvious when the talk involves math -- which I might discuss in a post of its own -- but the problem occurs with graphs, charts, diagrams, or any other high-content slides (which are otherwise great to have). Some try to solve the problem by creating handouts, but the problem isn't just that the audience doesn't have time to copy down the content -- they don't have the time to process it. Talks without slideware, by forcing you to present content at about the pace of writing, give the audience more time to think about the details and implications of what you're saying. Besides, the act of copying it down itself can do wonders for one's understanding and retention.
3. Most critically, slideware makes it easier to give a talk without really understanding the content or having thought through all the implications. If you can talk about something on an ad hoc basis, without the crutch of having written everything written out for you, then you really understand it. This isn't to say that giving a slideware presentation means you don't really understand your content; just that it's easier to get away with not knowing it.
4. Also, Tufte mentioned that slideware forces you to package your ideas into bullet-point size units. This is less of a problem if you don't slavishly follow templates, but even if you don't, you're limited by the size of the slide and font. So, yeah, what he said.
That all said, I think slideware is here to say; plus, it has many advantages over other types of presentation. So my advice isn't to not use slideware (except, perhaps, for math-intensive talks). Just keep these problems in mind when making your talks.
Posted by Amy Perfors at November 9, 2006 11:53 AM