The following advice for preparing and presenting a talk will help you maximize the impact of your talk on an audience and ensure that at a minimum they remember the take-away points of your talk. The points apply equally to research talks, lectures, and non-technical presentations.
I. Length of Presentation
A. The average attention span of an adult is 20 minutes.
1) Implication: you should ensure that the first 20 minutes of
your talk include any material that you want your audience to
remember.
2) Check it out: The next time you attend a talk look around after
25 minutes and see how many people are doing other things, such
as doodling, looking at laptops, reading papers, or dozing.
B. Prolonging Attention Span: You can prolong attention spans by
periodically giving your audience a rest. This can be done by
telling a story, giving a demo, or doing something else that
gives the brain a break. An analogy to what you are doing is
running hard for a few minutes, taking a break, then running
hard again. However, just as you will typically not be able to
run for as long after the break you cannot expect the renewed
attention span to last as long after the "break". In fact, count
on having only a couple of minutes.
II. Presentation Content
A. The 4 Golden Questions: Every research presentation should answer
the following four questions:
1. Where are we now?: In other words what is the current state of
the art before you started your research. Answering the
question "Where are we now?" will help define for the audience
the problem your research addresses.
2. Where are we going?: The answer to this question tells the
audience what you accomplished. It should be a high-level,
concise description, not a detailed description. Make sure
that you answer this question in the first couple minutes of
your talk. There is an old saying in the newspaper industry that
you should not bury the headline in the article. The same is
true of your talk. Do not bury the main results in the middle
of the talk. Not only might the audience miss them but you might
be past your audience's 20 minute attention span and they'll
have already tuned you out.
3. How did we get there?: Now you can get detailed and describe
the methods/techniques you used or invented to solve your
problem.
4. What is left for the future?: At the end of your talk you should
clearly state what problems are not addressed by your research
and are deferred to the future.
A good talk will provide brief answers to the first three questions
in the introduction and then hit the "where are we now" and "how
did we get there" questions in more detail in the rest of the talk.
B. When you change topics, summarize what you have discussed thus far
and how that relates to what you are about to discuss next. This
transition serves three purposes:
1. It provides a "break" for the audience
2. It sharpens your presentation by clearly separating topics
3. It gives listeners who have tuned you out a chance to get back
into the talk.
C. Introduce concrete examples before formal algorithms: Audiences
grasp algorithms much better if you
work through a concrete example using the algorithm before presenting
its formal specification.
D. Do a demo before discussing a software system in depth: The same
principle that applies to algorithms applies to software systems.
Listeners will have a much better idea of what you're talking about
if you demo your system before explaining implementation decisions.
III. Presentation Format
A. Fonts
1. Font Size
a. For large audiences use a font size of 18 or greater
b. For small audiences use a font size of 14 or greater
2. Font Family: Use a sans-serif font like Helvetica. The curls
that make serif fonts like Times Roman look so nice in
printed reports will cause blurring and eye strain when
projected to a large audience.
3. Font Style/Color
a. Use a plain font unless you wish to specifically highlight
a point
b. Do not use colors to "spice up" your presentation unless you
wish to emphasize a point. The human eye is naturally
drawn to changes in color so color can be useful for
emphasizing a point. However if you use color indiscriminately
then at best you are cluttering your presentation and at
worst you are wrecking the listener's concentration.
i An example of indiscriminate use of color is to color
consecutive bullets differently so that your presentation
has "variety".
ii. An example of the effective use of color is to use one
color for the header topic on the slide and a different
color for the bullets on the slide. The change of color
will highlight the header and draw the listener's eye
to the header, which is the first thing you want the
listener to read
B. Slides
1. The average time spent per slide at talks that I have attended
tends to be 1-2 minutes. When preparing a talk for a
particular duration you can divide the duration by this
average to come up with the approximate number of slides
you should use.
2. Limit the number of bullets per slide to five or fewer. There
are two reasons for doing so:
a. To reduce the clutter on the slide
b. To handle the limitations of short term memory
i Most people can hold 5-7 items in short term memory.
ii If you have five bullets on your slide then the majority
of your audience can remember the points you're
making without re-reading your slide. If you have
more than 5 items per slide than some of your audience
will be re-reading your slide and not listening
to you, thus missing presumably important information.
3. Make bullets short and snappy. Do not use complete sentences
unless stating a point that requires precision, such as a
theorem or definition.
a. Most people read all the text on a slide before
they start paying attention to what you are saying. Hence
the more text you have in your bullets the longer it will
take for people to start listening to you. If they take
too long they might completely lose the thread of thought
on that slide which can easily lead to a loss of
concentration for your entire talk, especially if you are
past the 20 minute threshold.
4. Color contrasts: A light font color on a dark background is
preferable to a dark font color on a light background because
the dark background will result in less glare.
a. Yellow or white on a blue or black background tends to
work best. Consider using one of yellow/white for the
header and the other for the bullets.
b. Do not clutter your background with fancy patterns or
graphics (e.g., your university's logo--everyone should
know where you are from from your first slide): They will
only clutter your slides, distract the listener from the main
point of the presentation and, in the case of fancy patterns,
possibly even reduce the readability of your text.
i. it is okay to use subtle background patterns as long as
they are unobtrusive.
c. When juxtaposing colors, try to use colors from opposite
sides of the rainbow. Colors that are close to one another
will appear to blur together and provide poor contrast. For
example, yellow appears much clearer next to black or blue
than it does to green. If you've forgotten the rainbow
an easy way to remember it is as Roy G. Biv (red, orange,
yellow, green, blue, indigo, violet).
5. A picture is worth a thousand words: When possible use pictures
to emphasize your points rather than text. Pictures can
succinctly convey information about processes, algorithms,
and software interfaces that could take hundreds of words
to convey. You will also use words to explain the pictures
so your verbally oriented listeners can focus on your words
while your visually oriented listeners can focus on the
picture. If you use text only then your visually oriented
listeners will be disadvantaged.
a. Do not use meaningless pictures (e.g., whimsical pictures)
to make your slides more
interesting. If you use a picture it should reinforce the
point you are making on the slide. Random pictures simply
distract your listener and clutter your slide.
6. Put a header at the top of each slide that succinctly summarizes
the topic of that slide.
7. Screen snapshots and program listings: Snapshots and listings are
next to useless if the listener cannot make out the graphics
or text.
a. Code listings
i. Most code listings I see in talks are unreadable.
Most presenters seem to recognize this fact because they
usually spend only a few seconds on the slide.
ii. Usually you care about only a few lines
of the listing so show only those few lines and either
use a bigger font or use a xerox machine or some other
tool to increase the font.
iii. Usually code listings are ineffective because the
listener is unfamiliar with the syntax. Hence the
listener spends precious time trying to decipher your
syntax while not listening to you.
iv. Bottom line: Unless the code is an integral part of
your results skip it in your talk. If you do include
it, then be prepared to spend a somewhat significant
amount of time on it so that the listener has a chance
to understand what you are talking about.
b. Screen snapshots
i. Most screen snapshots I see are unreadable because the
fonts are too small.
ii. Either use a xerox machine or other tool to enlarge
the image or edit your code to use bigger fonts before
taking the snapshots. As an example, a student of mine
needed to display a snapshot of an event recorder. The
event recorder displayed a list of events in a 12 point
font that was easy on a computer user's eye but unreadable
for an audience. The solution for the talk was to change
the font to a much larger point size and take a screen
snapshot. The event recorder displayed many fewer events
but who cared. The audience members only needed to see
one event to get the point.
iii. Do not let your talk become dominated by screen shots.
A live demo with its dynamicism will make your points
much more effectively than a series of static snapshots.
As with the snapshots, try to enlarge the point sizes
in your demo.
7. Use special effects judiciously: Powerpoint makes it possible
to fill your presentation with all sorts of "gee whiz" effects.
You should resist the temptation to use these effects unless
they actually enhance your presentation.
a. Example: Having bullets "fly in" is an example of a bad use
of special effects. Other than distracting your listener
and breaking his or her concentration, what purpose does it
serve?
b. Example: Fading in points right before you make them is
an example of a bad use of special effects. You can better
justify the fading in of bullets because it is less
obtrusive then flying them in and because it prevents the
listener from reading
the bullets before you're ready to present them. However, if
you've limited the number of bullets and kept them short
and snappy the listener can quickly assimilate the slide and
should already be listening to you. Fading in the points will
distract the listener and break his or her concentration.
c. Example: Fading in information to show what happens as an
algorithm manipulates a data structure is a good use of
special effects. For example, coloring the nodes of a graph
as they are reached in depth first search is an excellent
way to show how depth first search spreads through a graph.
In this case, the ability to present new information while
maintaining the same underlying picture maintains the
listener's concentration while moving to another slide will
break the listener's concentration and make it harder for
the listener to see what has changed.
IV. During the Presentation
A. You are your own worst critic: Most people are very self-conscious
when they give a talk. Fortunately, your audience is usually
concentrating so hard on trying to understand what you're saying
that they are not noticing the fact that your voice is shaking,
that you are backtracking in your sentences, or that you are
saying "uh" a great deal. Hopefully you can relax a bit if you
know that your audience is not hanging on your every little
imperfection.
B. Do not read your slides: Your listeners are perfectly
capable of reading and can do it more quickly than you can
recite them. If you've kept your bullets short and snappy you
won't be tempted to recite them because there will not be anything
to recite. It is okay to periodically recite a point, such as a
definition, to drive home a point. Just do not make a habit of it.
C. Bring a glass of water or some other beverage: Drinking during a
talk will lubricate your vocal chords and keep you from going hoarse.
D. Keep the presentation moving: Do not get side tracked by irrelevant
questions. It is okay to tell a listener that you will be happy
to discuss the question after the talk but that you need to move on.
1. If you are stumped by a question do not try to squirm your way
through it. If you're a good con artist you may be able to
fake your way through it but you're normally talking to an
educated audience that will nail you to the wall. It is much
better to move on to firmer footing and minimize the issue than
it is to make a big deal out of it and firmly implant it in the
audience's mind. For example, if you have not heard of a related
piece of research just admit it and move on.
2. If questions during a talk disrupt your flow it is ok to ask
the audience to defer their questions until the end of the
talk.
E. Try to keep yourself facing the audience as much as possible. It
is not necessary to make eye contact but your voice will carry
better and you'll be more likely to use body language that
enhances your presentation.