Why You Need Concise Powerpoint Slides
February 18, 2012 3 Comments
There are hundreds of books that will tell you how to give a Powerpoint presentation, but “be concise” tends to be a widely agreed upon starting point. The question remains, is it actually good to have brief slides, and if so, why? For example, do text-heavy slides create cognitive overload when they overlap with oral information, or are we simply bad at efficiently allocating attention between oral and written information?
Some new research by Christof Wecker gets at the answer to these questions. Wecker compared the amount of information retained from a variety of different presentations and found that 1) the retention of oral information is lower with regular (i.e. not concise) slides than with no slides, 2) in presentations with regular slides, the retention of oral information was lower than the retention of information on the slides, and 3) the suppression of oral information disappears when concise slides are used instead of regular slides. The lesson is that if your slides aren’t brief, you better not forget to put everything important on them.
The more intriguing part of Wecker’s study is what he found about the reason that slides can interfere with oral information. Wecker examined the cognitive load of subjects to determine whether or not there was a “redundancy effect” — i.e. a tendency for less learning to occur when the same information is given orally and in writing. He found no such effect existed. Instead, Wecker found that the suppression of oral information was correlated with the subjective importance a person placed on slides. In other words, slides interfere with the retention of oral information because people often judge information on slides to be more important. The generalizability of this finding is debatable because all the participants were university students, but I think it’s fair to say that college kids are a good stand-in for your average Powerpoint consumer.
The interesting question is why people are biased toward the written information. One explanation is that it’s some combination of laziness and an affinity for what’s known and controllable. The words on a slide are there, we can see them, and so why not take the easy way out and tell ourselves the slides are the most important thing. A more charitable explanation is that we learn better from slides because we can proceed through the information at our own pace. Perhaps we have unconsciously learned this lesson, and therefore we place more importance on slides because it’s a more efficient way of learning.
Wecker, C. (2012). Slide presentations as speech suppressors: When and why learners miss oral information Computers & Education DOI: 10.1016/j.compedu.2012.01.013