The Art of Scientific Presentations
Disclaimer:
This is a work in progress and will probably remain that way
forever. I
certainly don't pretend to know everything about giving
presentations. The advice in this document is simply a
compilation of the things I
have
observed and experienced in the course of my work. Everything in this document
concerns general situations. There will always be exceptions and
it is
up to the presentator to recognize these and adjust accordingly.
Allard Jan van Marle (March. 2008)
Last updated: 06/16/2008
Introduction:
Giving presentations is an integral part of scientific work. A
scientist has to be able to present his/her results to other
scientists, administrators and the general public. For some
people this
is easy, for others, not so much; but no-one can escape the
necessity. In this document I give an outline on how to prepare
and give a
presentation on a scientific subject. The main body of text deals
with
the preparation of slides because this
is a subject
on which objective advice can be given. While individual tastes
may
differ, one can honestly say that there are good slides and bad
slides. The actual presentation itself is a far more subjective
matter. What
works for one person may be a disaster for the next. Moreover, it
depends on the location, audience and personal skills of the
presentator. While I am able to give some general advice, I can
not
cover all possibilities in this one document.
The first stage of preparation is too ask oneself the following
questions (and find answers!).
What is the minimum amount of
information I want to present?
Quite often this is also the
maximum amount possible, due to time limitations and pre-existing
knowledge (or lack thereof) among the audience. You have to
decide
which information is crucial. This is going to be the basis of
your
talk. Anything else is a bonus and can be compromised with.
If you
think some information is still worthwhile, despite not being in the
critical category, you can make a few extra slides. They can come
in
handy when someone asks a question on that particular subject.
Who are my audience?
When giving a talk to specialists in the field you can dispense with
the general background. Anybody else and the background becomes
part of
the crucial information. Try to get an idea of the general
knowledge
among your audience and adjust your talk accordingly. Similarly,
not
everyone has the patience to listen to a lot of dry, technical
information. If you think this will become a problem you have to
find a
way to skip details
How much time do I have?
Running over time while giving a presentation is usually not allowed
and certainly not appreciated. This puts a constraint on the
number of slides and the amount of data on each slide. A good
rule: 2 minutes per slide. Under some circumstances you may
get away with one minute,
but it will always sound rushed. If you're slides are
particularly
crowded you may need more time, but this should be avoided in any
case. Also keep in mind that explaining figures and (especially!)
animations
can take several minutes.
What do I want from my audience?
If you want to impart information to fellow specialists, present method
and results. They already know the background and the
reasons. If you give a seminar to a whole faculty, go with
background and
results. The method is of secondary importance to these
people. Also
present them with the reasons why you do this research. Otherwise
they
may wonder what the point is. Is you presentation part of a job
interview? Now the method becomes
important again, as you want the audience to appreciate your skills and
the amount of work you put in. Do you want to get money from a
group of administrators? Better cut
back on the technical details. It'll just bore everybody in the
room.
Outline: Before you start making the
slides,
you should draw a general outline on paper. This will serve as a
guideline both for the slides and the things you are going to
say. The
outline should include: important information, the figures and
the sequence in which you will mention crucial points. The basic
rule:
You are going to say everything three times.
1) In the introduction
you tell the audience what you are going to say.
2) In the main part of
the talk you say it
3) In the conclusions you
tell the audience what you just said.
This may sound childish, but it works. The sequence is an
important part of the preparation. Some people
construct talks where they move back and forth between slides.
Try to
avoid this. It is confusing to the audience and you may well end
up
making mistakes and getting lost yourself. If you really think
you have
to show the same slide twice, by all means copy the slide! But
keep it
so that you only have to flip in one direction through your
presentation. Going back and forth just makes thing
awkward. For similar reasons I prefer not to use links in my
slides. Again,
clicking back an forth between the slides may confuse you as well as
the audience. Also, links to outside objects can easily be broken
when
you copy your presentation to a different system.
My general advice: Use the KISS
principal: Keep It Simple Stupid!
Narrative: Every story needs a narrative, a
storyline that ties the individual bits an pieces together and places
them in a general context. If you don't have a narrative, you'll
end up displaying a series of independent facts, without conveying any
idea on how they are related. How to make a narrative depends
entirely on what you are presenting, so I cannot do much more than give
some general tips.
1) Start with the big picture. Give the audience a general idea of
your research area. This allows them to place you presentation in
a larger context and makes them appreciate the relevance of you
work.
2) Show the audience an outline
of your talk. Make an
extra slide immidiately after your title. On this slide you show
a list of the things that you want to discuss. This gives the
audience some advance warning if your talk will cover a number of
different subjects. (N.B. This is the kind of slide that may need
to be removed to save time. If so, remember that you
removed it and make up for it verbally!)
3) First the problem, then the
solution. Once you have
presented some background, tell the audience what problem you are
trying to solve. Again, this gives your work relevance.
This means, that usually you'll start with something that is not
actually your own work. If you're a theoretician, start with the
observations you are trying to explain. If you're an observer,
start with the theory you want to test.
4) Make smooth transitions. Your slides should connect
to one another without gaps or jumps. E.g. If you present simulation
results, don't just confront the audience with a bunch of graphs.
Describe the type of simulation, the input and then the results.
Part of a smooth transition can be done vocally, but you should be
careful not to rely on this too much. It is easy to forget to say
something when you are standing in front of your audience, unless there
is an indication on the slide that you should do so.
5) Don't expect the audience to
remember. If you
mentioned something ten slides back, nobody will remember. You
either have to repeat it, or find a different sequence in which to
present the information. This is very important, if you have to
cover several different subjects and then tie them together.
Think about inserting a summary slide in which you explicitly show the
connection between the subjects.
5) Summarize. If there is any time at all,
summarize what you have said at the end of your talk. List the
key concepts and link them together. This gives the audience an
extra opportunity to make sense of your talk.
Preparing slides:
To me this is the most important part. Because it can be done in
advance, with a minimum of pressure, this is where you should focus
your
attention. A well prepared presentation that is pleasant to look
at and
imparts the information in a clear and concise manner will go a long
way, even if the speaker is nervous and stumbles a few times. On
the
other hand, poorly visible and/or chaotic slides can ruin a talk to
the point where it can not be saved no matter how brilliant the
research and/or the speaker. Modern software like Powerpoint has
made this a much easier job than
it used to be. On the other hand, it has also made the audiences
more critical and demanding. The time when you could get away
with a
couple of handwritten transparencies is past.
Generally: Keep your
slides empty! It is better to
have a large
number of slides, each with a little information, than a few slides
that are brimming over. Overfull slides are confusing and your
audience
will quickly give up on figuring out what it all means. Keep in
mind
what you intend to say during your talk. If you don't intend to
mention
something verbally, it shouldn't be on the slides either.
Visibility: This is the most important thing
and yet is often overlooked. The audience has to be able to see
what
is on your slides! If they cannot, they will lose interest in
your talk
very quickly.
This means good contrast, large letters, thick lines etc, etc.
Remember
during preparation that something may look good on a monitor, but may
be
completely invisible from a distance when it is projected on a white
screen. When in doubt, borrow a beamer and experiment.
Also,
keep the margins large. The beamer may have a different
resolution than your screen and the outer rims may be cut off.
You can
waste a lot of valuable time trying to adjust the settings. (See technical preparation)
Background color: A simple
thing, but of crucial
importance. Generally, a dark background with light letters works
better than the other way round. Choose a background color that
is easy
on the eyes and does not
distract from the actual information. Dark grey (as in this
document),
dark blue, Olive green
or British racing green, bourgondy etc. These are
all
good background colors.
Try to avoid colors that are too bright or intrusive, like tomato red or pink. Keep in
mind, that you may want to use several colors for your text and that
they must all be visible against the background. Black may work, but does not
always look good in projection.
DO NOT USE WHITE!!!!! EVER!!!!! This is one of the most
common
mistakes. A white background with black letters is NOT a good
idea. Remember, the room will most likely be dark, with the
screen as the main
light source. If this screen is completely white, the audience
will feel
like they're looking directly into a light bulb. Also, the bright
background will cause the pupils to contract, making it difficult
to see dark objects on the background (such as letters, figures
etc). E.g: It is
easy to see the
stars on a dark night, but difficult to spot
a small bird in a bright sky.
If you really want to use a light
background with dark letters, use light grey or blue or anything else,
as long as it is not bright. It'll spare
everybody a headache. The same applies to yellow to a somewhat lesser extend.
Both yellow and white
are great
colors for letters, but lousy colors for background
Also, be careful with background images or shapes. A little
doesn't
hurt, but it should not distract from the actual information.
Having
multiple colors in the background is usually not a good idea, since it
limits the number of colors available for the letters.
Letter color: This, of
course, depends on
the background. The main thing to keep in mind is contrast.
If the
background is dark, use light letters, with a different color.
White
letters tend to go well with any dark background. Yellow also works,
but should be reserved for titles, emphasis etc.
Dark letters of a different color on
a dark background can be
tricky and the colors must be chosen with care. Remember that
colorblindness (especially when it comes to distinguishing red and
green) is not
uncommon.
If the background is light, use dark letters. Never use light
letters
against a light background, even if they have a different color.
Combinations to avoid are:
Any combination of light green, yellow and/or
white. These are invisible on a projection screen.
Any combination of dark blue,
dark purple, dark red and/or dark green. These too become
invisible.
Red on green, or
visa versa, due to
colorblindness issues.
Text: When it comes to text on slides,
less is better. Don't put paragraphs of text on your
slides. Nobody is
going to read them. Use bullet points and short statements.
These are
mainly to remind you of what you should be saying and allow people to
make notes. Avoid playing around with the fonts too much.
Modern software makes
this easy, but that does not mean you should actually do it. Italics,
bold and underline can serve to draw
attention to words when used with
care. Use
them too much and everything will draw attention at the same time,
which means
that nothing will stand out anymore!
Little tricks like shadowed letters are better avoided. It just
makes
people wonder if they are seeing double. The same goes for colored
letters. Stick with one color and use one or two others for
special
cases like titles. If you change colors too often it will hurt
peoples
eyes and it loses its importance. Remember to use large letters
to maintain visibility.
Figures: 'A picture says
more than a
thousand words' may be a bit too much praise, but figures ARE the most
important part of a talk. This is where the results should be
displayed. Like text, figures must be visible. This means
lines must be thick, legends and titles must use large fonts
etc. It is tempting to use the same figures you put in your
papers, but
if you have the time, make new ones. It'll allow you to change
the
background (from white to something else), make thicker lines in your
graphs and enlarge the text. Remember the need for a clear
contrast
between lines and background. Here again the problem with
distinguishing red and green has to be considered,
not only for contrast, but also if you have multiple lines in one
graph. In case of multiple lines it is good to use more than one
distinction. e.g. continuous vs. dashed as well as
different colors. Also, don't put too much information in
each figure if you can help it. The audience will only see each
figure
for a minute or so. They won't have time to study it in
detail.
Surface contour plots make for clear, easily viewed figures. 3D
figures
or sculpted surfaces may look impressive, but detail is lost when
they are seen from a distance.
The file format is also a matter of considerable importance.
Postscript
(.ps, .eps, .epsi) and Acrobat (.pdf) formats are great for use
in text, but do not lend themselves well to use in
presentations. Instead, one should use a graphical format such as
.jpg, .gif, .tff
or .png. Remember that .jpg files are compressed, which leads to
a
loss
of resolution. PNG is probably the best format, since it is not
compressed and conforms to a single standard. (Unlike, e.g. tiff
files,
which exist in many subversions!)
Animations (I) Animated results: This is a difficult subject.
Animations are fun to look at and make your presentation more
attractive. However, they are difficult to use for the
speaker. For the
animation to be smooth, it has to go at a reasonable speed, which means
that the speaker has to time his comments carefully. There are
few
things so confusing to the audience as a speaker who is out of synch
with his animation. If you can, make an animation that you can
start
and stop whenever you want. This allows you to impart the
necessary
information in a timely fashion. If you cannot do this, just run
the
simulation once without speaking, then explain what is happening and
run it again. Don't use too many animations. They should be
the highlight of your
presentation.
Again, the file format has to be considered. Mpeg, animated .gif
and
.avi are the most common and least dependent on the platform.
Keep in
mind that you may have to port your animation to another computer
system, which makes compatibility a prime issue.
Animations (II) Enhancements:
This concerns
the animation schemes
made possible by modern presentation software. One can have text,
figures, symbols etc. flying in and out of the slides, bouncing,
zooming
and whatever. Be extremely careful with this. Most of the
time it is
just a giant distraction. One can use a slightly animated
transition
between slides to keep the audience attentive and let enumerated lines
of text appear one at a time. To do more is usually not a good
idea. Whatever you do, DON'T have anything move about on screen
that is not
directly related to what you are saying. It is extremely
distracting. The best thing is to use animations that occur only
when you push a
button. That way they will always be synchronized with your
talk.
Equations: Stephen Hawking states
that you lose half your audience every time you use an equation.
While
this may be a bit of a hyperbole, the point is extremely valid.
Putting
an equation on screen is risky. Few people can grasp the
implications
of an equation in the short time that a slide is being displayed.
If you want to show the relationship between quantities, a graph is
usually better. Still, under some circumstances it may be
necessary to
show equations (which may be a crucial result of your
work). If
so, keep them to the absolute minimum. Also, make sure that
people can
see the entire equation at once. If they have to combine
equations and
definitions in their heads they'll quickly get lost and at the very
least they'll be distracted from what you are saying.
Tables: Tables are boring. Try to
avoid
them and use graphs to display the information.
Whatever you do, don't put
the frontpage of your paper on a slide!
This was done in the
days of handwritten transparencies, because it was comparatively easy
to make a photocopy of a journal paper onto a transparency. Some
people continue this practice and turn the .pdf file of their paper
into a slide. Please, don't! It is unreadable, looks like
you were too lazy to make a proper slide and turns you into an object
of instant ridicule. Besides, it serves no purpose
whatsoever! You can type the title of the paper on a slide in a
few seconds and nobody is going to read the abstract or the
introduction when you show it to them for half a minute.
The spoken part:
Preparing the actual speech can be difficult. Making notes is not
a bad
idea, but use them for preparation only. Having notes during the
actual
talk can work counterproductive as you may end up reading from them
directly to the audience, which makes you look like an amateur.
If you think you
need a reminder to make sure you mention something, put it on the
slides. If it is that important it should be written down
anyway.
Once you have figured out what you want to say, I
suggest that you
practice a couple of times with a stopwatch to see how much time you
actually use. If it is too much, cut down on the
non-essentials. If possible, practice at least once in front of a
colleague. He or she
may have helpful comments and suggestions and may point out weak
spots. Once you are sure about the contents of your talk, keep
practicing. The
more you repeat it for yourself the better. It will keep
you from
making mistakes during the actual presentation and allow you to speak
more fluently.
While you practice, try to listen to yourself as much as possible to
see if you can spot any obvious problems.
For example: ....
1) Using the same word over and
over. Like in written text that can become very
boring. Try to
vary a little. Look up a synonym in a dictionary if you have
too.
2) Too many hesitations. A speaker who says Hmm and Ehh
all the time is very annoying for the
audience. Unfortunately some people have this habit and it can
get
worse if you have to speak in another language. If you know that
you
suffer from this problem, practice extra. Learn the whole speech
by
heart if you have to. It may sound rehearsed, but it'll keep the
audience from grinding their teeth while you are searching for the
right word.
3) Talking too fast. If
you have limited time, better cut back on the information.
Speaking
clearly on a few points is better than racing through many
points.
Language problems:
Most of the presentations you give will be in English. If that is
your
native language, fine. If not, take courses and/or practice until
you
are fluent. This is of crucial importance. Having an accent is by itself not a
problem as long as you can be understood, but if
people cannot understand you, they will stop paying attention.
Depending on your native tongue and your language skills this may be
more or less of a problem, but you HAVE to deal with it. Learning
the
talk by heart phonetically is not an option. Even if you have
perfect
recall, you'll be in trouble the moment someone asks a question.
Since
the scientific community is very international a good understanding of
written and spoken scientific English is always an advantage and well
worth the time and effort spent learning it.
Technical preparation:
Make sure in advance
that everything works (your laptop computer, remote control, laser
pointer
etc.) You will not have the time to do this once your presentation
starts.
Things to check:
Does my laptop work with the
beamer? (Not as much of a problem as it used to be, but it can
go wrong.) This is especially important with a Linux operating system,
which may have to be rebooted. Mac users should carry a connector
plug with them to be able to address
the beamer at all. Such a connector may not be available
locally.
Does the beamer show my
presentation correctly? Usually not a problem, but
sometimes
differences in resolution may lead to weird results. This can be
adjusted by resetting the resolution of your screen, but you have to
know how to do this. The minute your presentation starts is not a
good
moment to learn. A similar problem can occur with wide screen
laptops.
If a computer is provided by the
organizers, can my presentation be ported correctly? A major problem! transitions
between Mac, Windows and Linux can screw up your slides
completely. Fonts, figures and animations are all
vulnerable. A way to prevent this
is to use .pdf format rather than .ppt, but this may not be easy for
people who are not used to it. In case of trouble, use your
own
computer. If the organizers object, remind them, that the system
is
their responsibility. If it does not show your talk correctly,
they
have to fix it. In other words: put up, or shut up. Again,
this is something you should find out in advance.
If animations and figures in
your slides are put in through links to separate files, don't forget to
copy them! Again,
this
occurs often when porting a file to a different computer or saving it
onto a memory stick. In general, don't run the risk. Just
put figures
and animations into the presentation as complete files.
Remember Murphy's law: If anything can go wrong it
will! If you need an Internet connection for your talk, the
Internet WILL be
down. If the power cell of your laptop is weak, it WILL fail
during the
talk and there WILL NOT be a power source available. Take
measures in
advance to avoid such problems.
Despite all checks you may still
experience technical problems during your talk. If this happens,
don't
panic! Stay calm and try to fix the problem, or ask an organizer
to
help. Most people will understand perfectly. It can happen
to anyone.
The talk itself:
I
can not say too much on this subject. Some people find
speaking
in public easy, others don't. The experience is different for
everyone. A good preparation helps and may reduce
nervousness. If it doesn't,
just remember that you will not have to talk forever. Tomorrow
really
is another day.
During the talk, try to speak calmly and in complete sentences.
This
makes it easy for the audience to grasp what you are saying and you'll
probably find yourself speaking more confidently after a while.
Put in the occasional pause.
It'll let the listeners gather their
thoughts, make notes and phrase questions. It can also help you
think
about your next sentence. Transitions between slides are a good
moment
for a pause. These moments also give you time to look at your
audience and see if
they are still with you.
Take your time to explain figures and animations. They are the
most
interesting part of your talk and should get the lions' share of the
time. Make sure that you tell the audience what you are showing,
what
is on the axes, what colors signify etc.
Do not be scared of questions,
either during or after the talk. They
are not necessarily a criticism of you work or your presentation.
Instead,they may simply indicate that people are interested and paying
attention. If you
cannot answer a question immediately, don't be afraid to admit
it. It
is better to admit ignorance than to give a wrong answer. If you
really
don't know the answer, or think it'll take up too much time, say so and
ask the questioner to come and speak with you afterwards.
Questions can also give you an opportunity to elaborate on a subject
which you consider interesting but removed from your talk due to time
constraints. If you think this may happen, it is useful (and
makes a
good impression!) if you have a few extra slides handy.
Direct Attack This an unpleasant subject, but it
has to be dealt with. Sooner or later it happens to
everyone. Someone
in the audience doesn't like you, or your subject and instead of simply
asking a question launches a verbal attack that dismisses you and your
work as nonsense. If this happens, you have a problem. You
are
standing in the spotlight,
the attacker is in the half dark anonymity of the audience. You
have
only a few seconds to phrase an answer, the other had your entire talk
to prepare the question.
The first rule: stay
calm. Buy yourself a little time by repeating the
question, or ask the other to repeat his/her question. If you can
answer it correctly, do so, but calmly and politely. Do not get
drawn
into a shouting match. As long as you appear friendly and polite,
you'll hold the moral high ground. Many people in your audience
give
talks on a regular basis as well and will understand your
predicament.
Second rule: Don't
expect to accomplish anything. You cannot convince
fanatics that they are wrong. Answer the question but leave it at
that. If the question is repeated in a different form, or someone
argues that your answer doesn't address the question (a common tactic)
refuse to be baited. Repeat you answer once, if you think you
should
but no more than that. There should be a moderator/supervisor to
stop
the exchange from getting out of hand. If nobody does this,
you're out
of
luck and you'll have to do it yourself. Refuse a further answer
on the
ground that you already gave one and other people may have
questions. Also point out that a five minute question session is
not a good
format for an extended discussion. Your opponent may become
angry, but
that is actually a good
thing. If you can stay calm while the other loses control, you
will not
be the one who ends up looking like a fool.
(Be
careful! Some people are more verbally aggressive than
others and
phrase
their questions in a way that appears to be an attack without the
intention of being insulting. Don't become defensive unless you
have to
be.)
When it
comes to giving public
talks practice does not make perfect, but it helps. Especially if
you
can find a way to give the same talk more then once. The same
thing
goes for the preparation. Try to figure out what works for you
and what
doesn't. If this website has been useful to you, please check out
Steve Cranmer's website at:
http://www.cfa.harvard.edu/~scranmer/cranmer_htgat.html,
which provides links to
similar sites.