Since the mid-'90's I've been doing workshops training people to use Powerpoint and do it effectively and have had a web page with my workshop handouts and presentations. In the presentation I use to introduce the workshops, one of the things I recommend is the use of custom animation to introduce concepts on a slide as you get to them in your spoken presentation. Recently on a Physics Blog of all places, I saw a link to report of a study which found that using custom animation has a detrimental effect on learning!
Coincidentally, I was looking at my web site's Google Analytics today and noticed my Powerpoint page has been getting a few more hits than usual lately, so out of curiosity, I googled "Powerpoint instruction" to see where I landed. The last time I did this a couple years ago, I quit looking after 50 pages. Today, it was number four on the first page! I'm going to have to be more careful about what I'm shooting my mouth off about–and the first thing I thought about was this study about custom animation.
In an article titled "The Dark Side of Custom Animation" published in The International Journal of Innovation and Learning, Stephen Mahar, Ulku Yaylacicegi, and Thomas Janicki of the University of North Carolina Wilmington compared two classes who used the same recorded lecture with a synchronized Powerpoint presentation. One was set to present each element on a slide as it was presented, and the other to present the the whole slide at once. They found that students could recall more details of the slide presented all at once, than with the one progressively disclosed. (I've only seen the abstract and blog summaries of the article, but I've got an interlibrary loan request in for the whole thing).
My fondness for what I've always called progressive disclosure, long before Powerpoint existed, is based on several ideas.
Back in the stone age, probably the biggest abuse of overhead transparencies was to put practically your entire presentation on one transparency. They were relatively expensive, kind of bulky to drag around, and a bit of a distraction to change during your presentation (Although they were kind of fun to throw like a frisbee into the audience if you had a good stiff mount). The bad things about this were that regular typewriter type (12 pitch for you oldsters) was a little small to be read from even the middle of the room, not to mention the back row and it also gave the audience something to read while you were speaking. I'm pretty skeptical of the idea of multi-tasking, especially when the tasks are reading and listening. If I'm reading something, I lose track of what's being said.
I said earlier that people put their whole presentation on one transparency. Well it was more like an outline of their whole presentation, so when reading the outline, the audience was probably missing the full detailed story the speaker was saying. The same thing is true of Powerpoint. (If the text on the slide is exactly what you're saying, you're already doing badly enough that no technique is going to save your presentation).
You (again those of you old enough) may remember presenters attempting to do "progressive disclosure" by sliding a paper down the transparency revealing only what had been covered by the presenter. With illustrations we used to have multiple overlays which could build up to the complete visual. (I had an instructor in AV grad school who referred to this as selective revelation, which has a spooky religious sound to it). This is exactly the idea behind custom animation in Powerpoint.
In addition to missing out on what's being said while reading, the audience may skip ahead to the end, and start wondering about how you reached the conclusions, instead of listening to you explain how you did. Revealing on your slide the parts of an argument or process as you talk about them seemed to me to allow you to concentrate the audience's attention on what you were saying rather than having them get ahead of you.
In the age of Powerpoint, in many presentations I've found myself listening to a presenter expounding on a list of points on a slide, and realized I'm not sure which point they're talking about. Looking at the slide doesn't help me clarify anything, and I lose more of the spoken presentation reading the list on the slide. It seemed to me that presenting the slide one point at a time would keep me focused on the subject being dealt with right now.
My basic point is that I thought progressive disclosure, on an overhead transparency or with Powerpoint, concentrated the power of the projected visual to focus the attention of the audience, allowing you to develop a concept point by point. The Mahar et al study seems to contradict this.
I'm curious to see the slides used in this study. Were they just lists of bullet points, labeled illustrations or diagrams of processes?
Did the students have access to the slides after the lecture? Could it be a matter of better note taking from the static slide? Would they do better if given access to the slides after the lecture so they could concentrate on the presentation and have the illustrations to review later?
There is an alternative in Powerpoint that would preserve my need to know which part of a slide was currently being talked about, and to also have the entire slide available. One of the classes of effect in Powerpoint is Emphasis, whereby the element being acted upon is made to look different–one assumes more noticable–when it's place in the order is reached. Using this instead of the Entrance effect would help the audience stay synced between the spoken presentation and the visual on the screen, and preserve the enhanced retention effect the Mahar et al study seems to have identified. It wouldn't keep the audience from reading ahead, but maybe that's not such a detriment to understanding I thought it was.
When I get the whole article maybe I'll send some of these questions to the authors. Maybe they'll google themselves and find this blog and submit a comment!