Preparing an Effective Presentation

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.

Length of Presentation

1. 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.

2. 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.

Presentation Content

1. 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.

2. 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.

3. 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.

4. 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.

Presentation Format

1. Fonts
   1. Font Size
      1. For large audiences use a font size of 18 or greater
      2. 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
      1. Use a plain font unless you wish to specifically highlight a point

      2. 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.
         1. An example of indiscriminate use of color is to color consecutive bullets differently so that your presentation has "variety".

         2. 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

   4. 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:
         1. To reduce the clutter on the slide
         2. To handle the limitations of short term memory
            1. Most people can hold 5-7 items in short term memory.
            2. 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.
         1. 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.
         1. 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.

         2. 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.
            1. it is okay to use subtle background patterns as long as they are unobtrusive.

         3. 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.
         1. 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.
         1. Code listings
            1. 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.

            2. 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.

            3. 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.

            4. 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.

         2. Screen snapshots
            1. Most screen snapshots I see are unreadable because the fonts are too small.

            2. 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.

            3. 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.

      8. 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.
         1. 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?

         2. 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.

         3. 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.

During the Presentation

1. 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.

2. 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.

3. Bring a glass of water or some other beverage: Drinking during a talk will lubricate your vocal chords and keep you from going hoarse.

4. 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.

5. 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.