How to give a technical presentation (how to give a scientific talk) (2023)

by Michael Ernst

January, 2005
Last updated: March 21, 2022

Contents:

  • Introduction
  • The content
  • The slides
  • The presentation
    • Answering questions
  • In-class presentations
  • Practice talks
  • Other resources

Introduction

(Also see my advice on giving ajob talk and onmaking a technical poster.)

A successful career depends on the ability to give effectivetechnical presentations, whether at a conference, toyour research group, or as an invited speaker.This pagenotes some problems that I very frequently see in talks.

Get feedback by giving multiple practice talks! Oneof the most effective ways to improve your work is to see the reactions ofothers and get their ideas and advice.

Think about the presentations you attend (or have attended in the past),especially if they are similar in some way to yours. What was boring aboutthe other presentations? What was interesting about them? What did youtake away from the presentation? What could you have told someone aboutthe topic, 30 minutes after the end of the presentation?

The content

Before you start preparing a talk, you need to know your goal and know youraudience. You will have to customize your presentation to its purpose.Even if you have previously created a talk for anothervenue, you often need to make a new one, particularly if the audiencediffers or you have done more work in the meanwhile.

The goal of a talk you give to your research group is to get feedback tohelp you improve your research and your understanding of it, so you shouldplan for a very interactive style, with lots of questions throughout. In aconference talk, questions during the talk are unlikely, and youhave much less time; your chief goal is to get people to read the paper orask questions afterward. In a seminar or invited talk, youwant to encourage questions, you have more time, and you should plan to givemore of the big picture.

The goal of a talk is similar to the goal of atechnical paper: to change theaudience's behavior. Therefore, you should also read and follow my adviceabout writing a technical paper.Decide what the change is, and focus your talk around that.Typically, you have done someresearch, and to effect the change you need to convince the audience of 3 things: the problemis worthwhile (it is a real problem, and a solution would beuseful), the problem is hard (not already solved, and there arenot other ways to achieve equally good results), and that you havesolved it. If any of these three pieces is missing, your talk ismuch less likely to be a success. So be sure to provide motivation foryour work, provide background about the problem, and supply sufficienttechnical details and experimental results.

When you give a talk, ask yourself, “What are the key points that myaudience should take away from the talk?” Then, elide everything that doesnot support those points. If you try to say too much (a tempting mistake),then your main points won't strike home and you will have wasted everyone'stime. In particular, do not try to include all the details from atechnical paper that describes your work; different levels of detail and adifferent presentation style are appropriate for each. Never paste PDF ofa table from a paper to slides. Reformat the table to be more readable andto remove information that is not essential. The talk audience does nothave as much time to comprehend the details as a paper reader does.

Before you create slides, a good way to determine what your talk should sayis to explain your ideas verbally to someone who does not alreadyunderstand them. (You may use a blank whiteboard, but that often is notnecessary.) You may need to do this a few times beforeyou find the most effective way to present your material.Notice what points you made and in what order, and organizethe talk around that. Slides should not be an obstacle that constrains yourtalk, but they should support the talk you want to give.

Do not try to fit too much material in a talk. About one slide per minuteis a good pace (if lots of your slides are animations that take onlymoments to present, you may have more slides). Remember what your keypoints are, and focus on those. The key point should be written on theslide, for example as its title or as a callout. Don't present moreinformation than youraudience can grasp; for example, often intuitions and an explanation of theapproach are more valuable than the gory details of a proof. If you try tofit the entire technical content of a paper into a talk, you will rushand the audience may come away understanding nothing.It's better to think of the talk as an advertisement for the paper thatgives the key ideas, intuitions, and results, and that makes the audienceeager to read your paper or to talk with you to learn more. That does notmean holding back important details — merely omitting less importantones. You may also find yourself omitting entire portions of the researchthat do not directly contribute to the main point you are trying to make inyour talk.

Just as there should be no extra slides, there should be no missing slides.As a rule, you shouldn't speak for more than a minute or so without havingnew information appear. If you have an important point to make, then havea slide to support it. (Very few people can mesmerize an audience on atechnical topic, and leave the audience with a deep understanding of thekey points, without any visual props. Unfortunately, you are probably not oneof them.) As a particularly egregious example, do notdiscuss a user interface without presenting a picture of it — perhapsmultiple ones. As another example, you should not dwell on the title slidefor very long, but should present a graphic relevant to the problemyou are solving, to make the motivation for your work concrete.

The slides

Slide titles.Use descriptive slide titles. Do not use the same title on multiple slides(except perhaps when the slides constitute an animation or build). Choose adescriptive title that helps the audience to appreciate what the specificcontribution of this slide is. If you can't figure that out, thenyou do not yet understand your own material.

Introduction.Start your talk with motivation and examples — and have lots ofmotivation and examples throughout. For the very beginning of your talk,you need to convince the audience that this talk is worth paying attentionto: it is solving an important and comprehensible problem.Your first slide after the title slide should be motivation, such as anexample of the problem you are solving.

Outline slides.Never start your talk with an outline slide.(That's boring, and it's too early for the audience to understand the talkstructure yet.) Outline slides can be useful, especially in a talk thatruns longer than 30 minutes, because they help the audience to regain itsbearings and to keep in mind your argument structure.Present an outline slide (with the current section indicated viacolor, font, and/or an arrow) at the beginning of each major section of thetalk, except for the introductory, motivational section.

Conclusion.The last slide should be a contributions or conclusions slide, remindingthe audience of the take-home message of the talk. Do not end the talkwith future work, or with a slide that says “questions” or“thank you” or “the end” or merely gives your emailaddress. And, leave your contributions slide up after you finish the talk(while you are answering questions). One way to think about this rule is:What do you want to be the last thing that the audience sees (or that itsees while you field questions)?

Builds/animations.When a subsequent slide adds material to a previous one (or in some otherway just slightly changes the previous slide), all common elements mustremain in exactly the same position, pixel-for-pixel. A good wayto check this is to quickly transition backand forth between the two slides several times. If you see any jitter,then correct the slide layout to remove it. You may need to leave extraspace on an early slide to accommodate text or figures to be insertedlater; even though that space may look a little unnatural, it is betterthan the alternative. If there is any jitter, the audience will know thatsomething is different, but will be uneasy about exactly what has changed(the human eye is good at detecting the change but only good at localizingchanges when those changes are small and the changes are smooth). You wantthe audience to have confidence that most parts of the slide have notchanged, and the only effective way to do that is not to change those partswhatsoever. You should also consider emphasizing (say, with color orhighlighting) what has been added on each slide.

Keep slides uncluttered.Don't put too much text (or other material) on a slide. When a new slidegoes up, the audience will turn its attention to comprehending that slide.If the audience has to read a lot of text, they will tune you out, probablymissing something important. This is one reason the diagrams must besimple and clear, and the text must be telegraphic. As a rule of thumb, 3lines of text for a bullet point is always too much, and 2 full lines isusually too much. Shorten the text, or break it into pieces (say,subbullet points) so that the audience can skim it without having to ignoreyou for too long.

Do not read your slides word-for-word. Reading your slides verbatim isvery boring and will cause the audience to tune out. You are alsoguaranteed to go too fast for some audience members and too slow forothers, compared to their natural reading speed, thus irritating manypeople. If you find yourself reading your slides, then there is probablytoo much text on your slides. The slides should be an outline, not atranscript. That is, your slides should give just the main points, and youcan supply more detail verbally. It's fine to use the slides as a crutchto help you remember all the main points and the order in which you want topresent them. However, if you need prompting to remember the extradetails, then you do not have sufficient command of your material and youneed to practice more before giving your talk.

Just as you should not read text verbatim, you should not read diagramsverbatim. When discussing the architecture of a system, don't just readthe names of the components or give low-level details about the interfacesbetween them. Rather, explain whatever is important, interesting, ornovel about your decomposition; or discuss how the parts work together toachieve some goal that clients of the system care about; or use othertechniques to give high-level understanding of the system rather thanmerely presenting a mass of low-level details.

(It's possible to overdo the practice of limiting what information appearson each slide, and you do want to have enough material to support you ifthere are questions or to show that the simplified model you presentedverbally is an accurate generalization. But the mistake of including toomuch information is far more common.)

Text.Keep fonts large and easy to read from the back of the room. If somethingisn't important enough for your audience to be able to read, then it probablydoes not belong on your slides.

Use a sans-serif font for your slides. (Serifed fonts are best for readingon paper, but sans-serif fonts are easier to read on a screen.)PowerPoint's “Courier New” font is very light (its strokes arevery thin). If you use it, always make it bold, then use color orunderlining for emphasis where necessary.

Figures.Make effective use of figures. Avoid a presentation that is just text.Such a presentation misses important opportunities to convey information.It is also is wearying to the audience.

Images and visualizations are extremely helpful to your audience. Includediagrams to show how your system works or is put together. Never includegeneric images, such as clip art, that don't relate directly to your talk.For example, if you have a slide about security, don't use the image of apadlock. As another example, when describing the problem your work solves,don't use an image of a person sitting at a computer looking frustrated.Just as good pictures and text are better than text alone, text alone isbetter than text plus bad pictures.

When you include a diagram on a slide, ensure that its background is thesame color as that of the slide. For example, if your slides have a blackbackground, then do not paste in a diagram with a white background, whichis visually distracting, hard to read, and unattractive. You should invertthe diagram so it matches the slide (which may require redrawing thediagram), or invert the slide background (e.g., use a white slidebackground) to match the diagrams. A light-colored background with darktext is usually the best choice (preferably white background with blacktext; see the next paragraph about eye candy).

Do not use eye candy such as transition effects, design elements thatappear on every slide, or multi-color backgrounds. At best, you willdistract the audience from the technical material that you are presenting.At worst, you will alienate the audience by giving them the impression thatyou are more interested in graphical glitz than in content. Your slidescan be attractive and compelling without being fancy. Make sure that eachelement on the slides contributes to your message; if it does not, thenremove it.

Emphasis.Slides that are monocolor black on a white background can be boring. Thistires the audience, and it may prevent them from appreciating the bigpicture. Use color, callouts (e.g., arrows or speech bubbles), or othermechanisms to draw attention to the most important parts of your slides orgraphs. For example, suppose you have a list of 3-5 bullet points, eachone line of text long. You might want to emphasize the 1-3 most importantwords in each bullet point.

Color.About 5% of American males are color-blind, so augment color with otheremphasis where possible. For example, on an outline slide, in addition tocolor I use boldface and also a right arrow (⇒) in the left margin toindicate the current section of the talk.

The presentation

Make eye contact with the audience. This draws them in. It also helps youdetermine when they are confused or have lost interest, andwhether your pacing is too fast or too slow.

Stand and face the audience.

  • Don't give a talk while seated. Standing gives you more energy, the talk is more dynamic, and it is easier to maintain eye contact.
  • Do not face the screen, which puts your back to the audience. This is offputting, prevents you from getting feedback from the audience's body language, and can cause difficulty in hearing/understanding you. Do not look down at your computer, either, which shares many of the same problems.
  • Don't stand in front of the screen. This prevents the audience from viewing your slides.
  • Being animated is good, but do not pace. Pacing is very distracting, and it gives the impression that you are unprofessional or nervous.

When giving a presentation, never point at your laptop screen, which theaudience cannot see. Amazingly, I have seen many people do this!Using a laser pointer is fine, but the laser pointer tends to shake,especially if you are nervous, and can be distracting. I prefer to use myhand, because the talk is more dynamic if I stride to the screen and use mywhole arm; the pointing is also harder for the audience to miss. You musttouch the screen physically, or come within an inch of it. If you do nottouch the screen, most people will just look at the shadow of your finger,which will not be the part of the slide that you are trying to indicate.

If you find yourself suffering a nervous tic, such as saying “um” in themiddle of every sentence, then practice more, including in front ofaudiences whom you do not know well.

If you get flustered, don't panic. One approach is to stop and regroup;taking a drink of water is a good way to cover this, so you should havewater on hand even if you don't suffer from dry throat. Another approachis to just skip over that material; the audience is unlikely to know thatyou skipped something.

Think about your goal in giving the talk. When presenting to your ownresearch group, be sure to leave lots of time for discussion and feedbackat the end, and to present the material in a way that invites interactionafter and perhaps during the talk. (When presenting to your own group, youcan perhaps give a bit less introductory material, though it's hard to gowrong with intro material. It should go quickly for that audience; youensure that everyone is using terms the same way; andit's always good to practice presenting the motivation, context, background,and big ideas.)

For computer science conferences, the typical dress code is “businesscasual”. (For men, this is a dress shirt with slacks or jeans.) Some peopledress more formally, some more casually. The most important thing is thatyou are comfortable with your clothing; if you are not, your discomfortwill lead to a worse presentation.

Answering questions

Answering questions from the audience is very hard! Even after you becomevery proficient at giving a talk, it will probably take you quite a bitlonger to become good at answering questions. So, don't feel bad if thatpart does not go perfectly, but do work on improving it.

Just as you practice your talk, practice answering questions — boththe ones that you can predict, and also unpredictable ones. Givepractice talks to people who are willing to ask such questions.

When an audience member asks a question, it is a good idea to repeat thequestion, asking the questioner whether you have understood it, beforeanswering the question. This has three benefits.

  • You ensure that you have understood the question. When thinking under pressure, it can be far too easy to jump to conclusions, and it is bad to answer a question different than the one that was asked. A related benefit is that you get to frame the question in your own words or from your own viewpoint.
  • You give yourself a few moments to think about your answer.
  • If the audience member does not have a microphone, the rest of the audience may not have been able to hear the question clearly.

Be willing to answer a question with “no” or “I don'tknow”. You will get into more trouble if you blather on or youmake up an answer on the fly.

In-class presentations

For an in-class presentation by a student, you will be judgedon how well other people understand the material at the end of the class,not on how well you understand the material at the beginning of the class.(You do need to understand the material, but that is not the main point.)

When you present someone else's paper in class, you should cover not only the technicaldetails (people generally do a good job of this), but also what is noveland why others didn't do it before. That is just as important but veryoften overlooked. Focus on what is important about the paper, not just onwhat is easy to explain or to give an example for.

Know what your main point is, and don't get bogged down ineasier-to-understand but less interesting details.Try not to bring up a topic until you are ready to discuss it in detail —don't bring it up multiple times.

Encourage questions — it's the best way to deepen understanding —and be able to answer them. If other students wrote questions in areading summary, be responsive to them. When you ask a question,don't assume the answer in the form of your question. For example, don'task, “Was there anything novel in the paper, or not?” but “What was novelin the paper?” It can be very effective to ask a question that revealsunderstanding of a subtle or easy-to-misunderstand point (but an importantone!) in the paper, because this will lead the audience members to reflectboth on the paper and on the way they read and understood it.Don't be too abstruse, and don't get bogged down in unimportant detailsjust to show your mastery of them.

Examples are often very helpful.Augment your talking with visuals on the board or slides. Either is fine.The board may encourage more interaction (and it slows you down in abeneficial way), but does require pre-planning; don't just go up and startdrawing. Most people find comfort in having pre-prepared slides, andslides can be a good choice because they can be more legible and detailed,can include animations, etc. Don't waste a huge amount of time onelaborate slide decks, though; that is not the point.

Practice talks

Always give at least one practice talk before you present in front of an audience.Even if you have read over your slides and think you know how the talk willgo, when you speak out loud your ideas are likely to come out in adifferent way. (This is true about writing, too: even if you knowwhat you want to say, it takes several revisions to figure out the best wayto say it.) In fact, you should practice the talk to yourself —speaking out loud in front of a mirror, for example — before you giveyour first practice talk. In your individual practice session, you must say everyword you intend to in the actual talk, not skipping over any parts.

It can be a good idea to keep your practice talk audience relatively small— certainly fewer than 10 people. In a large group, many peoplewon't bother to speak up. If the pool of potential attendees is largerthan 10, you can give multiple practice talks, since the bestfeedback is given by someone who has not seen the talk (or even thematerial) before. Giving multiple practice talks is essential forhigh-profile talks such as conference talks and interview talks. Avoid asmall audience of people you don't trust, who might be unanimous in a wrongopinion; getting a balance of opinions will help you avoid makingtoo many mistakes in any one direction.

Videotape yourself to see how you come across to others. Thisinformation can be a bit traumatic, but it is invaluable in helping you toimprove.

When giving a practice talk, number your slides (say, in the corner), evenif you don't intend to include slide numbers in your final presentation.

When giving a practice talk, it is very helpful to distribute hardcopyslides (remember to include slide numbers) so that others can easilyannotate them and return them to you at the end of the talk. (Also, theaudience will spend less time trying to describe what slide their commentapplies to, and more time writing the comment and paying attention to you.)For non-practice talks, don't give out hardcopy slides,as they would tempt the audience to pay attention to the piece of paperinstead of to you.

Go to other people's practice talks. This is good citizenship, andcultivating these obligations is a good way to ensure that you have anaudience at your practice talk. Furthermore, attending others' talks canteach you a lot about good and bad talks — both from observing thespeaker and thinking about how the talk can be better (or is alreadyexcellent), and from comparing the feedback of audience members to yourown opinions and observations. This does not just apply to practicetalks: you should continually perform such introspective self-assessment.

(Also see Tessa Lau's advice on giving apractice talk— which focuses on a practice talk for a PhD qualifying exam, but isrelevant to talks in general.)

Other resources

Here are some other good resources for speakers who wish to give a goodtalk.

See IanParberry's speaker's guide.

The LaTeX Beamerdocumentation has some good advice.

Back to Advice compiled by Michael Ernst.

Michael Ernst
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