However, there is some evidence informal which tells us that the use of slides makes the oral information that is transmitted is not retained by the listeners. But, why?
The explanation most widespread is related to the concept of cognitive load: simply, we would be unable to process both types of information (oral and contained in the slides). However, it seems that the cognitive load has not been demonstrated conclusively in this type of presentations. What is what happens then?
The psychologist Christof Wecker, in a recent article, has another theory: the oral information is lost because listeners pay more importance to the information offered by the slides.
Wecker is part of a cultural observation: in most contexts today, a presentation without a set of slides is not an option. And this fact implies another deeper: the oral presentation has gone on to be a comment on the slides, so the slides become the message itself, instead of a means for supplementing.
This change in the dynamics of the presentations is accompanied by a change in the expectations of the listeners regarding the content and aspects of the situation: a information on a slide is likely to be perceived as a signal which shows its importance. Attention so is redistributed: it reduces the attention to the speech that accompanies the presentation, and increases the attention to the content of the slides.
Of course, the attendees of the presentation may differ in terms of their expectations and beliefs about the content of the same, so it is expected that those individuals that provide a greater subjective importance to the slides show a lower retention of oral information.
If this mechanism were true, according to Wecker, this redistribution of attention would be glossed over with the use of slides concise that, on the one hand, contain a limited amount of information, and on the other hand, they leave areas of the presentation without visual support.
Thus, Wecker started with two hypotheses that show:
In the first place, that the lack of retention of oral information is due not to the cognitive load, but to the redistribution of the attention due to a greater subjective importance attributed to the slides.
In the second place, that the lack of retention of information is more pronounced when using slide show detailed, so that it can be glossed over with the use of slides concise.
Wecker used to 209 students of a bachelor’s degree in Education. The study took place in the context of a course on the search for information in libraries and electronic resources. The course was divided into three presentations of 30 minutes each (dedicated to the system of scientific publication, methods for the search of scientific literature, and the ways of access to the information found). During the presentations, not allowed students to take notes (even though they said that at the end of the course would receive a script of course).
The presentations responded to three conditions experimental:
- A presentation without slides
- A slide show with detailed information: all the topics of the presentation they had a slide; the slides include definitions, examples, and key principles
- A presentation with slides concise: not all the topics of the presentation they had a slide; in addition, they only consisted of a list of key points, without definitions or examples
After the presentations, the students had to answer a test of 18 questions with four answer choices, more than 3 questions with a response format open. The questions in the test were designed in such a way that you could get an idea of the retention of information by students during the three types of presentation.
Wecker needed to get an idea of the cognitive load that the presentations had been of course for the students, as well as the subjective importance given by them to the slides, which could explain the results.
To estimate the cognitive load, the students had to answer one question: “How difficult has been to follow the presentation?” The answer had 7 options, from “very easy” to “extremely difficult”.
To estimate the importance granted to the slides, the students had to answer three questions with a scale of answers from 1 (“completely agree”) to 5 (“absolutely agree”). The questions were: “I Prefer PowerPoint presentations to traditional”, “The slides in PowerPoint are very useful to follow a presentation” and “PowerPoint slides are required to memorize the content of a presentation.”
The results of the various tests confirmed the hypothesis of Wecker. Let’s separate the facts that confirm this:
As to whether the lack of retention of information is more pronounced when using slide detailed, and if that lack of retention can be glossed over with slides concise, Wecker found that:
- The retention of oral information was lower with the slides detailed without slides
- The withholding of information from the slides was higher than the retention of verbal information on the status of the slides detailed
- The retention of information overall was highest in the condition of the slides concise than in the conditions without slides and slides detailed
Therefore, it was confirmed that the slides detailed hinder the retention of oral information, and that the slides concise help to alleviate this lack of retention.
In terms of the process that is hidden under that lack of retention:
On average, students assessed their cognitive load with an average score on the scale “extremely easy” – “extremely difficult” in the conditions without slides and slides detailed. In other words: the students found more difficult to follow the presentation, with slides detailed the presentation without slides, so that a loss of oral information by excess of information was discarded.
As we said at the beginning, if the loss of oral information is related to the importance that subjects attributed to the slides, then subjects them to attribute more importance would be those who are more verbal information would be lost. And that was what Wecker found: there was a significant difference in information retention between students who had declared to give a lot of importance to the show, and those who had declared to give them little importance.
Of the results, Wecker draws two practical implications:
The first implication is that it reinforces the idea that the presentations should be based on slides concise, but with two nuances:
In the first place, if little is known about the hearing, or it is possible that the audience has different expectations about the importance of the slides, then better to stick to the slides concise. For other types of audience, use of slides detailed may not be problematic.
In the second place, depending on the theme it may not always be easy to include all the necessary information in the diapostivas, so it will be necessary to have a detailed oral explanation. You have to get there as well to balance complex, since more information in the slides, and to more subjective importance of these, it is easier for the necessary oral information is lost.
The second implication is related to the cultural fact that we mentioned at the beginning of the post: it is necessary to understand that the best presentations are those that are based on what the speaker says, rather than what is being projected on a wall and which is commented on by the lecturer. Com says Weckr, this is the more interesting challenge.