The effectiveness of visualisations compared to text slides in
lectures
Wim Blokzijl1, Bas Andeweg2
1
Delft University of Technology, Institute of Technology and Communication, P.O.Box 5015, Delft, The
Netherlands. ([email protected])
2
idem ([email protected])
Abstract:
Oral presentations in business situations and in classrooms are usually accompanied by a set of slides, projected
by a video projector. Typically, these slides are in a text format. This seems a bit odd; many columns have been
written about the tediousness of presentations that are supported by endless numbers of bullet slides.
Generally, audiences seem to feel that using true visualisations – pictures, diagrams, graphs etcetera - is a better
idea. But is it really? Maybe not, because while this may enhance the attractiveness of the presentation, it may at
the same time obstruct learning because it overloads short-term memory.
In a large scale experiment, using a real life 15 minute lecture, four types of visual support were compared: (1)
no visual support at all; (2) concise text slides; (3) extensive text slides; (4) real visualisations. A comparison
was made between these visualisation types by offering the lecture to technical students, who were divided into
four groups, each of which was presented a different kind of visual support.
The findings of the study indicate that, from a learning point of view, visualisations are not always the best way
to support lectures. From a learning perspective, text slides seem to be more effective.
Keywords: experimental research, visuals, PowerPoint, presentation
1. INTRODUCTION
One of the choices presenters have to make is whether or not they will use some sort of support. Should they
employ PowerPoint or not? Using PowerPoint means choosing for extra preparation time and for the risk of
equipment failure or relaying on a more personal elocution. If PowerPoint is chosen, the next question is again
one of preparation time: taking the short route of only text slides, or taking the more creative route by visualising
the contents of the speech. Of course, it is not only a question of preparation time – although this is an important
factor in itself - but also of effectiveness. Which way of presenting will yield the larger crop?
Common sense would have real visualisations to work best: after all, text slides just summarise what the speaker
says and do not add any information. In addition, text slides are generally considered to be boring; see for
example [1]. Yet true visualisations – pictures, diagrams, graphs etcetera - do have drawbacks as well. They may
be more captivating, but recent studies into multimedia presentations indicate that they can overload working
memory, resulting in curbed learning. Last, there are voices that state that PowerPoint inherently induces
stupidity – whether the slides contain text or visualisations [11].
Although there are quite a lot of theorists and communication trainers who advise presenters on what choices to
make, research on this subject is scarce [12]. It is time to really find out what a presenter has to do to achieve
maximal clearness in a presentation.
Purpose & organisation of this paper
In this paper, we present the results of a study into the effectiveness of different types of visual support. We
compare four different types of visual support: concise text slides, extended text slides, slides with real
visualisations and no slides at all.
This paper is organised as follows. First, we will discuss the aforementioned multimedia studies that question the
effectiveness of real visualisations. The next chapter will describe the design of our experiment. Then, the results
will be described and discussed.
2. RECENT MULTIMEDIA STUDIES
At oral presentations, audiences usually receive visual as well as auditory information. According to dual coding
theory, these two information flows are processed separately, respectively through the visual and the auditory
channel [9]. Written text is considered to be visual information, because it is - at first, anyway - being processed
in the visual channel. Learning can take place if the audience can combine visual and auditive information to a
coherent model [6]. In presentations, this is the case when a presenter’s visual support is directly related to his or
her speech.
However, it is not sufficient when visual and auditive inputs are combined. According to limited capacity theory,
our short-term memory (STM) is quite small (e.g. [7], [10] and [5]); therefore, offering too much information
will lead to a memory overload. At presentations, this happens when a presenter talks too fast or when there’s
too much information on the slides. Consequently, listeners will understand and remember less of the lecture.
Limited capacity theory assumes the presence of only one STM, in which visual as well as auditive information
is processed. Recent multimedia research questions this, and suggests that visual and auditive information are
processed separately (e.g. [3]). This would mean that, when visual memory is overloaded, auditive STM doesn’t
necessarily have to be overloaded as well, and vice versa.
A presentation that is visually supported, carries the conditions that can make an STM overload happen. And
indeed some experiments have been carried out in which this phenomenon occurred. Studied however were not
common lectures, but multimedia presentations; presentations that were watched from behind a computer. Yet
these presentations were designed in a way that made them similar to common presentations in many ways.
Research into PowerPoint usage in real life presentations is missing. The next paragraphs describe three
multimedia experiments and their results.
Kalyuga, Chandler & Sweller studied to what extent STM overload occurs when a multimedia presentation is
extended with written text [4]. Their experiment went as follows. All their experimental subjects were offered a
graph in which characteristics of solder were reflected. This graph was built up in steps during the presentation,
just as often happens in PowerPoint presentations.
The subjects were divided into three groups. Each of them had the graph explained in a different way:
• Group 1 heard a spoken explanation through headphones.
• Group 2 saw a written explanation, by means of short texts that appeared on the screen next to the graph.
• Group 3 got the spoken explanation as well as the written one.
Afterwards, all groups were tested on retention and understanding. The group that was given both oral and
written explanations turned out to perform worst; the group that was only given the oral explanation performed
best.
Mayer, Heiser & Lonn [6] describe comparable research. They also studied the effects of written text as a part of
a multimedia presentation. The design of their experiment was almost the same as that of Kalyuga, Chandler &
Sweller. An important difference however, was that their groups were not presented with a graph, but with an
animated film about the origin of lightning. At the same time, they heard a voice through headphones that
provided an explanation of the film.
The experimental subjects were divided into three groups:
• Group 1 saw the entire text, as it was spoken, word-by-word on a screen.
• Group 2 saw a written summary on the screen.
• Group 3 saw no written text at all.
Afterwards, all groups were tested on retention and understanding. The result: the group that saw no text at all
scored best; differences between the other two were not significant.
In both studies the authors explained their results with the limited capacity theory: the groups that saw text on
the screen had to pay attention to the text and to the graph or film at the same time. This caused their visual
short-term memory to overload. The authors designate this specific case of information overload as split
attention; it is a form of overload that takes place when an audience has to process two kinds of visual
information – in this case a text as well as a graph or animation.
An additional explanation could be that the summarising text was effectively quite extensive; all sentences were
shortened a bit, but were kept grammatically correct. Maybe the groups in question would have performed better,
had the text been more concise.
The third experiment that is relevant for our research is of Moreno & Mayer [8]. It is a follow-up of the abovementioned experiment conducted by Mayer, Heiser & Lonn [6]. Again, subjects were presented with an
explanation about the origin of lightning. However, this time they were not shown an animated film. All subjects
heard a voice through headphones that gave an explanation. The subjects were divided into two groups:
• Group 1 just heard the voice, and saw nothing.
• Group 2 heard the voice and saw the entire text, as it was spoken, on a screen.
Afterwards, when tested on retention and understanding, the group that saw and heard the text outperformed the
other group. The authors explain that this was due to the absence of pictures; this prevents the split attention
effect from occurring. This reduces chances of visual short-term memory overload to occur. So in this case,
written text enhances retention as well as understanding.
3. PURPOSE OF THE STUDY
What can be concluded from these multimedia research results? Are the observed effects applicable to oral
presentations? Not automatically - after all, an oral presentation is not the same as a multimedia presentation.
Still, the setup of these experiments was quite similar to oral presentations. So let us suppose for the moment that
the multimedia results also go for these oral presentations: this would mean that supporting a presentation with
either text slides or visual slides would do the trick. What works best, however, remains to be seen. And suppose
we use text slides, would it be beneficial to adopt the famous 6 by 6 rule (‘Thou should not put more than six
words – or, in some variations, syllables - on a line and no more than six lines on a slide’; some advisers refer to
the 7 by 7 rule). These are important questions for raw presenters like our students.
Therefore, the purpose of our study was to establish whether a presentation supported by slides with
visualizations or slides with text (bullet points for example) would work better (in contrast to a non-supported
presentation). Secondly, we wanted to know if meeting specific layout criteria - like the 6x 6 rule – would make
the slides more effective. This study is part of a larger PhD study into the techniques of presentation support. In
an earlier study – partly based on the same material as this paper – we observed that an able presenter without
slide support was outperformed (in the sense of listeners recollection of what was presented in the speech) by a
less communicative presenter with slide support [2]. So it is important to get hold on the more specific clues on
how to support a presentation.
4. DESIGN OF THE EXPERIMENT
Presentation
A lecture was written and designed specifically for this research. The subject of this lecture was the application
of persuasion techniques in communication. We expected this subject to be interesting for the intended audience:
students in public speaking. The lecture had a length of 2140 words and took approximately 15 minutes to
present.
Visual Support
We distinguished three main presentation support conditions:
1 A presentation without visual support (without ppt)
2 A presentation supported with text slides
3 A presentation supported with real visualisations (visualisation ppt)
The text condition was split into two subconditions: slides with extensive text (extensive ppt) and slides that
meet the 6x6 rule (the concise ppt). For each of the conditions (except of course without ppt) we designed a
PowerPoint presentation.
The concise version was designed according the rules in the advisory literature; the extensive version did not
follow those guidelines. The two PowerPoint presentations differed on the amount of content and consequently
on the layout of the slides themselves. By choosing a large, 32-point letter font we ensured that all the slides
were legible. Table 1 summarises the differences between the two versions.
Extensive ppt
Grammatical units: sentences
26 slides
850 words (incl. titles)
averagely 32,7 words per slide
averagely 6,1 lines per slide (excl. titles)
averagely 4,6 words per line (excl. titles)
averagely 9,2 syllables per line (excl. titles)
font: 32 point (Arial)
content: 45 main points
content: 20 details
Concise ppt
Grammatical units: key words; telegram style
15 slides
230 words (incl. titles)
averagely 15,3 words per slide
averagely 3,5 lines per slide (excl. titles)
averagely 3,5 words per line (excl. titles)
averagely 7,8 syllables per line (excl. titles)
font: 32 point (Arial)
content: 29 main points
content: 6 details
TABLE 1: Differences between PowerPoint text support versions
Table 1 shows that the extensive version of the slides contained over 3,5 times as many words as the concise
version. The concise version follows the 6 by 6 rule: it stays well within the advised margins. We would
compliment a student on this type of design. The extensive version does not follow the standard presentation
guidelines. Although the average amount of text on a slide is more or less within acceptable limits, some slides
were clearly too crammed (eight lines, title excluded; lines consisting of ten words). In this version, key words
were almost exclusively used in titles. The body of the slides consisted mainly of complete sentences; these
sentences were not literal duplicates from the text that was spoken by the presenter.
The difference that is made in table 1 between so-called main points and details was defined as follows (see table
2 for an example of the differences between the two versions):
Main points: A main point was defined as an important informative element of the text, such as an element a
student would typically need to know for an exam or an element that he or she wants to memorize, like a
definition. Main points are also the elements that aid in remembering those central informational points like words/sentences that clarify the text structure. Summaries (or repetitions of main points) were
considered as main points too.
Details: A detail was defined as an element that was of no or little importance to the story line. It has an
illustrative, elucidative function: an example, an illuminating kind of information or an acknowledgment.
Details can often be derived from the main points. Sometimes they are interesting to know, but not
essential to learn for an exam.
A verification of the usability of the above-mentioned informal definitions was carried out by two judges (not the
authors), both of them communication trainers. They independently sorted the sentences of the extensive
PowerPoint version in main points and details. This resulted in a reasonable agreement between them expressed
in a Cohen’s κ of .72. In conclusion: with the use of these definitions the content of both PowerPoint
presentations can be reasonably characterised.
Spoken text: [...] You want to change behaviour. That intention does not always lead to the desired effect. How can that be? It
is necessary to determine the nature of the behaviour we are speaking about. Normally we distinguish two kinds of behaviour:
planned behaviour and automatic behaviour. Planned behaviour is behaviour we contemplate. We weigh up the pros and cons.
Planned behaviour is the decision of people to get married, to get divorced or to start a study in Management and Technology.
Approximately five percent of our behaviour is planned behaviour. The remaining 95 % is automatic behaviour. That is
behaviour we do not consciously contemplate: we call it routine behaviour. If we had to contemplate every act or bodily
movement when we are riding a bike then we would have tumbled down before long. If you would have to consider each
morning what manoeuvres you have to make to get up, you would not leave your bed. But you just think ‘I have to go to
college’ and the funny thing is that you start a large series of automatic behaviour […]
Concise support (one slide):
Types of behaviour
• Planned behaviour
Behaviour we contemplate [5%]
• Automatic behaviour
No conscious contemplating [95%]
Extensive support (three slides):
Types of behaviour
There are two kinds of behaviour: planned and automatic
behaviour.
Planned behaviour
Planned behaviour is behaviour that we contemplate
consciously
Examples are the decisions to get married, to divorce or to
study Management & Technology.
5% of all behaviour is planned behaviour.
Automatic behaviour
Automatic behaviour is behaviour we do not consciously
contemplate. Routine behaviour.
Examples are the acts that we have to perform to rise from
bed every morning or the movements we have to make when
riding a bike.
95% of all behaviour is automatic behaviour.
TABLE 2: Example of the differences between extensive ppt and concise ppt
Next, a slide show with real visualisations was designed. The basis for this slide show was the extensive text
slide version. Each text slide was translated into a slide with one or more visualisations. This led to a slide show
that consists of various types of visual elements. Figure 1 (ABCD) gives examples of the constructed slides.
A
B
C
D
FIGURE 1: examples of slides with visualizations
Translating text into images cannot be done mechanically; there are numerous ways to visualise text, and
different translators will inevitably have different ideas about the best possible translation. Our starting point was
to transpose words into images (photos, drawings) as much as possible. If this proved impossible – when for
example a definition had to be transposed - diagrams or charts were used. The visualisations can be described as
follows:
• Diagrams (see example C, D): loose, framed words that are often connected by lines or arrows.
• Photographs (see example A, B): a number of photographs of researchers that are mentioned in the
presentation. A photograph of Einstein. Photographs of people who wake up or who propose to marriage.
Photographs were often combined with other visual elements. Some images contained words as well (for
example a photograph of a car with a text sticker attached to it).
• Charts (see example A): simple pie charts.
• Drawings (see example B): simple drawings of - for example - a packet of cigarettes , a roadblock or a
seesaw. There was one cartoon. One drawing was animated (a moving car).
• Negations: on four slides, the visualisation was crossed out to indicate that something was not the case (for
example: a photograph of a glamorous political campaign was crossed out to indicate that glamour doesn’t
work in information campaigns).
Inevitably, text was part of the visualisations. A diagram without text would have been incomprehensible. And
of course, all slides carried titles. However, none of the slides contained any autonomous text.
Experimental subjects
The sample consisted of 237 first and second year student engineers of Delft University of Technology, who
took a compulsory course in public speaking. The experiments were carried out at the beginning of the course:
they hadn’t had any instruction in the use of PowerPoint at that phase in the programme.
Questionnaire (multiple choice text/opinion questions)
A three-part questionnaire was developed to collect information on the subjects and to obtain an impression of
the effect that the presentation had on them. Firstly, the students were asked to give an indication of the amount
of foreknowledge they had on the subject of communication and behavioural change on a five-point scale.
Furthermore they were asked whether they thought that a lecture on this subject was necessary and interesting
for this group of students (on a five-point scale as well).
Secondly, to measure the effect in information transfer through the lecture (with or without visual support), we
developed a multiple choice questionnaire with 30 items (Cronbach’s α = .75). The multiple choice-questions
related to the main points of the lecture as well as to the details. The information needed to answer the questions
was of course incorporated in the spoken text of the lecture. A number of the answers could also be retrieved
from the various text slides. The mc-questionnaire was made up of three parts:
a. spoken text only: the answer of 7 questions could only be retrieved from the spoken text, not from the slides;
b. extensive version: the answer of 11 questions could also retrieved from the set of extended (and visual)
slides;
c. concise and extended version: the answer of 12 questions could also be retrieved from both sets of slides.
A third part of the questionnaire contained statements (with an accompanying five-point scale) to measure the
attitudes of the students regarding the presenter, the presentation and (when applicable) the projected PowerPoint
presentation. These aspects are related to the informative and persuasive power of a presentation. Five factors
were measured:
• ethos of the speaker (3 statements; Cronbach’s α .68): the professionalism of the speaker: his trustworthiness
and credibility;
• attractiveness of the presentation (3 statements; α .80): did the presentation stir the curiosity of the listeners;
• comprehensibility of the presentation (2 statements; α .77): was the contents of the presentation
comprehensible;
• quality of support of the PowerPoint slides (3 statements; α .75): the listener felt assisted by the slides in
comprehending the lecture;
• informational quality of the PowerPoint slides (2 statements; α .76): the listeners thought they got most
information from the slides (as opposed to the speaker).
The experiment
The context of the research - a course in public speaking – called for a situation that would be quite similar to a
normal lecture. A laboratory approach would be less useful. To this end, a lecture-like or conference-like kind of
presentation was chosen: the lecture was presented live by a skilful teacher, unknown to the subjects in order to
prevent bias effects in a normal classroom. All sessions were videotaped to control for possible differences in
presenting style. It turned out that the teacher’s way of presenting was rather stable.
The students received the lecture with the explanation that it was a part of their regular course. They were told
that the faculty staff was doing an educational experiment that necessitated combining training courses with
formal lectures. This also explained why they had to fill in the questionnaire directly after attending the lecture.
A week later the students were again asked to complete the same questionnaire. Afterwards they were debriefed
on the experiment. Table 3 shows that the students appeared to have rather little prior knowledge on the subject,
that they thought the given information to be somewhat interesting and that it was a useful addition to the public
speaking course they were following.
Foreknowledge
I already knew a lot about
this subject.
Subject interesting
I think a lecture about this
subject is interesting.
Lecture necessary
I think a lecture about this
subject is necessary for an
engineer.
Condition
Mean
Std. Deviation
N
without ppt
2.55
0.978
38
extensive ppt
2.67
0.606
43
concise ppt
2.67
0.883
48
visualisation ppt
2.61
0.972
106
Total
2.63
0.894
235
without ppt
3.42
0.948
38
extensive ppt
3.42
0.794
43
concise ppt
3.63
0.866
48
visualisation ppt
3.53
0.907
106
Total
3.51
0.884
235
without ppt
3.29
0.835
38
extensive ppt
3.47
0.827
43
concise ppt
3.71
0.771
48
visualisation ppt
3.26
0.908
106
Total
3.40
0.868
235
TABLE 3. Prior knowledge, interest and need of the experimental subjects
The groups hardly differ on the aspects mentioned in table 3 (F (9, 557.476)=1,275 p=.247). More detailed
analysis, however, revealed a lower score of the visualisation ppt group compared to the concise ppt group on
‘Lecture necessary’ (F (2, 231)=3,262 p<.05 Bonferroni post hoc test). This outcome did not correlate to the
results of the multiple choice-questions. In contrast, the statement ‘I think a lecture about this subject is
interesting’ díd correlate with these results (r=0.23 p<.001).
5. RESULTS
The results are split into three sections: the students’ scores on the multiple choice-test (5.1), their opinions on
the lecture (5.2) and their opinions on the PowerPoint support (5.3).
5.1 Multiple choice-test
The main dependent variable was the score on a multiple choice knowledge test. This test turned out not to be an
easy assignment. The maximum score was 30 correct answers; on average the students (N=237) answered just
above 18 of the questions (60.5%; in the remainder percentage scores will be used for easy reference) correctly
(range 23-90%). Table 4 presents the differences that were measured directly after the presentation; figure 2
presents the differences that were measured one week later.
Condition
Mean*
Std. deviation
N**
without ppt
54.79
16.326
39
a
extensive ppt
65.89
12.907
43
b
concise ppt
62.57
16.159
48
b
visualisation ppt
59.53
12.742
107
Total
60.70
14.534
237
b
* percentage correct answers on multiple-choice test
** a/b superscript: difference is significant (p<0.01)
TABLE 4. Presentation support variations directly after the presentation
Table 4 shows that any form of visual support does improve the students’ scores on the multiple choice-test:
there’s a significant difference between the without ppt group (score 54.8%) and the other (visual or text) groups
(mean score 62.7%) (F(1, 235)=7,53 p<0.01).
Further analysis of the differences between the groups that received any kind of visual support, yielded
significant differences (F(1, 196)=5.56 p<0.05). The text support condition (combined concise ppt and extensive
ppt groups; mean score 64.2%) outperformed the visualisation ppt group (score 59.5%). The outcomes after one
week are less striking. Figure 2 shows the general decline of the multiple-choice scores after one week. It is
interesting to note that a week after the presentation concise ppt performed slightly worse that visualisation ppt,
while directly after the presentation it was the other way around. However, differences between the four groups
after a week are no longer significant (F(3, 210)=2,053 p=0.11).
70
65
60
55
50
45
Direct
After w eek
Without PPT
Extensive PPT
Concise PPT
Visual PPT
FIGURE 2. Scores of students on the test directly after the presentation, and one week later
The second research question concerned the degree of conciseness of the text slides. The observed differences
between the concise ppt condition and the extensive ppt condition turned out to be non-significant. The results
on the subparts of the questionnaire roughly reflect the results on the complete questionnaire. Table 5 shows
that there is an advantage for the extensive PowerPoint group where it concerns the ‘answers in extensive ppt’
subpart (although the difference is not significant: t(89)=1.89 p=.06). In the subpart of the questionnaire, where
the answers could be found in both supporting PowerPoint slides, the battle between the two is unresolved. The
absolute difference - advantage for the concise version - is far from significant and must be attributed to chance.
Total MC score
Answers in speech text only
Answers in extensive PPT
Answers in both PPT
Condition
Mean
Std. Deviation
N
Extensive PPT
65.89
12.907
43
Concise PPT
62.57
16.159
48
Extensive PPT
55.15
22.389
43
Concise PPT
55.06
21.043
48
Extensive PPT
68.50
13.506
43
Concise PPT
62.69
15.605
48
Extensive PPT
69.77
16.267
43
Concise PPT
66.84
20.230
48
TABLE 5: differences between subparts MC-test
In the third part of the questionnaire, the students were presented with a number of statements with regard to
aspects of the speaker and the presentation itself. Three factors were measured. A multivariate test showed that
there was an effect for the kind of presentational support (F(6, 456)=3.13 p<.05). Table 6 presents the
differences between the groups. Further analysis made clear that the effects could be attributed to the perceived
comprehensiveness of the lecture. No differences could be observed for the attractiveness of the lecture or the
perceived ethos of the speaker.
Type of support
Comprehensive lecture
Attractive lecture
Ethos of the speaker
Mean*
Std. Deviation
N
0.826
38
No support
3.42
a
Text slides
3.78
b
0.584
89
Visualisation slides
3.56
0.826
106
Total
3.62
0.751
233
No support
3.07
0.939
38
Text slides
3.19
0.790
89
Visualisation slides
3.28
0.785
106
Total
3.21
0.813
233
No support
3.53
0.692
38
Text slides
3.48
0.754
89
Visualisation slides
3.63
0.642
106
Total
3.55
0.695
233
* a/b superscript: difference is significant (Bonferroni post hoc test, p<0.05)
TABLE 6. Opinions on lecture
A multivariate analysis of the opinions of the listeners on the type of support made clear that there was an effect
for type of support (F(2, 189)=12.197 p<.001). Table 7 presents the differences between the conditions.
Text or visuals
Slides as informational source
Support quality
Mean*
Std. Deviation
N
Text
2.68
0.840
86
Visuals
2.61
0.805
106
192
Total
2.64
0.819
Text
3.08
a
0.787
86
Visuals
3.61
b
0.770
106
Total
3.37
0.820
192
* a/b superscript: difference is significant (p<0.05)
TABLE 7. Opinions on PowerPoint support
Further analysis made clear that the perceived quality of the slides made the difference. The listeners to the
presentation with the visualized slides evaluated the quality of support higher than the listeners who got the
textual support. The slide show as source of information for the listeners appeared approximately the same in
both cases.
6. CONCLUSIONS
The purpose of this study was to compare the effectiveness of a text slide support versus slide support with
visualisations Before we discuss those differences, the most obvious result must be stated first: the group that
was abstained from PowerPoint support scored significantly lower on the subsequent knowledge test. In a
regular school-testing programme, this could have made the difference between passing and failing grades. So
supporting an informative lecture with slides seems to be a sensible decision. This result seems to corroborate
the research results of Moreno & Mayer [8]. However, caution is required. Firstly, in our study only one single
presentation was used. This presentation was rather far off from the instructional presentations that our
experimental subjects - student engineers - normally get. Maybe the outcome would have been different with a
more science-like presentation on for example the origin of lightning. Secondly, there is the construction of the
type of visuals in the slide show. We tried our best to make the slides as informative and attractive as we could,
but it is reasonable to assume that a professional – and highly paid - designer could surpass our work.
Are visuals more effective than bullet points? This question is rather loaded - bullet point slides are generally
denounced. Our study shows that our students have a clear-cut opinion on how they like their support: visuals
are judged better than the text slides. However, the multiple-choice test shows that there is more than just liking a
kind of support. It seems that a speaker who uses text slides attains that his students will remember the rather
difficult contents better; presentations that use text slide support seem to be superior in an educational
environment. However, the differences that occurred directly after the presentation lose their significance already
after one week.
The famous 6 by 6 rule (or variants of it) does not seem as vigorous as we expected. The observed differences
between the groups were not significant: the absolute differences were even in favour of the extensive version of
the slides. Analysis of the subparts of the knowledge test confirms this result. Information that was included in
the extensive slides was reproduced better by the group that saw these slides than by the group that saw the
concise support version. Questions for which the answers were on both PowerPoint versions, were answered
equally well by both support groups. Some reserve to the outcome is necessary. Maybe our breach of the 6 by 6
rule was not severe enough. We did put more text on the slides, but they stayed legible altogether. The
characteristic nature of the field experiment - it was carried out in the context of a real course in oral presentation
skills - did not allow us to go to extremes.
An interesting question is whether results from multimedia research are directly transferable to the practice of
oral communication. Not just like that, we think. The laboratory-like experimental setup in multi-media research
differs greatly from the kind of real life field setup we choose for. Our setup has a disadvantage: it is much
harder to precisely explain the observable remembrance effects. On the other hand the this setup makes the
research possible at all. The applied character of this type of communication research suggests a more direct
connection to the educational setting from which the original research question arises: what is the best way to
support a presentation?
References
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Curricula
Wim Blokzijl, MA (1971) received a master's degree in applied linguistics at the University of Groningen, 1996.
Since 1997 he has worked at TU Delft, where he co-ordinates and teaches courses on oral and written
communication. He does research into the effectiveness of visual support at oral presentations, and into audience
appreciation of PowerPoint. He regularly publishes articles on a variety of communication subjects.
Bas Andeweg, PhD (1952) is assistant professor. He lectures on oral and written communication. Recently he
has finished his Ph.D. project The introduction of speeches (together with Jaap de Jong of Leiden University),
about different aspects of speech introductions; for example about the effectiveness of different kinds of
introductions (www.deeersteminuten.nl). He publishes regularly on subjects in the fringe of human
communication and internet technology.