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Education research

Powerpoint can reduce learning success

München, 05/27/2014

Nowadays, it is almost impossible to attend a lecture that doesn’t use Powerpoint slides. But do they make it easier to retain the substance of the talk? In the following interview, LMU educational researcher Christof Wecker discusses their impact on learning.

Nowadays, it is almost impossible to attend a lecture that doesn’t use Powerpoint slides. But do they make it easier to retain the substance of the talk? In the following interview, LMU educational researcher Christof Wecker discusses their impact on learning.

Foto: Jan Greune
Source: Jan Greune

What use are Powerpoint presentations?
Christof Wecker:
In terms of knowledge acquisition, it doesn’t make a great deal of difference whether Powerpoint slides are used or not. Some 40 studies, of varying quality, have been published since the mid-1990s, which have measured learning outcomes following exposure to lectures with and without digital slides. I have subjected these papers to a so-called meta-analysis, which revealed that there is only a negligible effect. Listeners learn a little bit more when the lecturer uses such slides. But strikingly, even this holds only for cases in which the slides projected displayed nothing but text. As soon as you put in tables or graphics, or even sounds, videos or animated transitions between slides, the effect vanishes.

Have your own experiments yielded similar results? And how does one measure the effect of Powerpoint?
My own studies have been carried out partly in live lectures and partly under laboratory conditions. In the latter case, the subjects watch a video of a real lecture which is shown in life-size on a big screen. This enables us to implement identical conditions, except that slides are either included or not. We can interrupt the lecture at certain points to ask questions about a topic that was mentioned shortly before. We use eye-tracking devices to ascertain whether our subjects are engaged in reading at various points, and we analyze the notes they take during the lecture. The results show that, after lectures with slides, students often retain less of the spoken information than they do when no slides are shown, although this deficit apparently does not arise from failure to register what was said.

What aspect of Powerpoint then accounts for the difference? Is it just a matter of the demands of multitasking, listening and reading at the same time?
The data actually point in a different direction. They suggest that the spoken word is regarded as secondary – as supplementary explanation for example – while the slides are judged to be the bearers of the real message. We find that students more often note down the text displayed on the slides, while the information conveyed orally by the lecturer is not recorded. In the first study I did on this topic, I found that those who were most convinced that the slides were the important thing retained comparatively little of the information communicated orally by the lecturer.

In light of these results, how should lecturers proceed?
One conclusion one might draw is: “Then I must put everything on the slides.” But that leads to lectures that nobody wants to listen to, and it poses new problems. If I’m giving a 90-minute lecture, I must be able to react to questions, and I must assume that the audience is listening to what I am saying.

What about dispensing with slides altogether?
Actually, this is an option that people seldom consider. Nowadays, anyone who gives a talk at a conference and doesn’t use slides at all is likely to be regarded as somewhat eccentric. The middle way is not to project slides all the time. In one study, I looked at the effects of minimal use of slides, and I inserted black slides so that the screen was dark between times.

And did it work?
Yes, that’s what the results indicated. I often use this approach in my own lectures and the effect is unmistakable. When the screen goes black for the first time, the “shock” among the audience is palpable, and the listeners suddenly begin to pay attention to the actual presentation. That’s not the file with the “ppt” suffix on the computer, it is the whole live situation, someone standing out in front and speaking to an audience. We have unfortunately become accustomed to taking the slides on the screen for the heart of the matter.

Has Powerpoint actually changed how lectures are given?
Definitely – and not always for the better. Many lecturers treat their slides as a substitute manuscript, and project their aide-memoires onto the screen for all to see. And very often the lecturer is the only person who needs to have all this information written down. This habit also has the effect of inhibiting any didactic consideration of what the listeners need to see and should be shown. Instead, everyone gets to look over the lecturer’s shoulder. Why should a text that was written for an entirely different purpose be of any great help for learning?

What should the audience be shown then?
Graphics that convey a particular message more effectively than can be done by the spoken word are very useful – a diagram which makes it possible rapidly to grasp certain relationships between different factors, for instance.

Does it help if the slides are made available to the audience beforehand?
Students adore slide sets! There‘s plenty of evidence for that in the literature, and my own experience confirms it. If one distributes slides in advance, the question is what the students do with them, and what learning strategies they apply. If one uses the slides to prepare for the lecture, maybe even consults a textbook or reads up on the background, then one can take helpful notes on the printouts. But if one comes unprepared and just brings the slides along to the lecture, then one is less likely to benefit from the oral explanations supplied by the lecturer.

It might be a good idea to coach people in how best to combine listening and note-taking during Powerpoint presentations. Simply being aware of the fact that concentrating on the slides may cause one to miss what is being said might even be sufficient. But these are issues on which research is still lacking.

Newer forms of presentation, such as the online tool Prezi, are now available. Is Prezi any better?
In most cases, whether the information is presented on a wooden blackboard or in high-tech form with the aid of Prezi will be entirely irrelevant. Prezi allows one to create visualizations in the style of a Mind-Map, where one can zoom in and out during a presentation. But it would be naive to think that the medium alone makes much of a difference. Media open up possibilities, but one must know how to use them appropriately. And to do that one has to look beyond the current conventions. Unfortunately, researchers have so far concentrated almost entirely on comparing lectures with slides to lectures without slides. Now we need to find out which design features of slides in combination with situational factors produce the best results. For example, it would be important to investigate whether, and under what circumstances, diagrams and images alone, without any text, or stepwise presentation of slides, section by section, can promote learning – even though the studies published so far suggest that they do not.

Interviewer: Nicola Holzapfel

Christof Wecker

PD Dr. Christof Wecker is a Lecturer at the Chair of Education and Educational Psychology at LMU. His current research project on “Hazards for Knowledge Acquisition in Presentations” is funded by the Deutsche Forschungsgemeinschaft.