Speak your science: How to give a better conference talk

Bad presentation often gets in the way of good science. It's a shame, because science is awesome. So if you're a scientist who's interested in improving how you present your science, read on.

This post is a revised and updated version of one I wrote in 2013. Here's a recording of me giving this talk at the Lunar and Planetary Laboratory at the University of Arizona on February 5, 2018. 

I can summarize my advice in three words:

Respect your audience.

Each one of the people in your audience is another person, like you. Their time is as valuable as yours. Work to deliver them a presentation that is designed for them, to inform and interest them in your work, and to leave them pleased that they spent that 5, 10, or 50 minutes of their valuable time listening to you.

Here are some questions to guide you in preparing a good talk.

To whom are you speaking?

Think carefully about your audience. Who are they, and what can you assume about what they already know about your topic? Is it an audience of your peers within your subspecialty? Is it space scientists more generally? Is it scientists and engineers? Is it a funding body? If it's the public, do they come to the room knowing a lot about space? Or is it a general audience?

The wider an audience you are addressing, the more context you will need to provide to them. If you do not provide the people in your audience with the information that they require in order to understand you, it is the same as telling them that you do not care if they understand you or not.

For a scientific conference, I suggest targeting your talks at an audience that is familiar with the scientific process but whose subspecialty is entirely different from yours. Are you an astronomer? Pitch your talk to a geologist. An experimenter? Pitch your talk to a theoretician.

Really good speakers are ones who manage to communicate something to everybody in the room, no matter who they are or how much they already know. To the relatively uninformed, you should at least answer: What is the question behind your work, and why is it important? What did you learn, and why does it matter? At the same time, to the well-informed, you should convey how your work has added to, broadened, or contradicted what has come before it.

Identifying your audience allows you to identify what words are jargon and what are not. Words are wonderful things, and our subspecialties have a lot of vocabulary that is dense with information. But if a word is not familiar to your audience, it will confuse rather than clarify. Sometimes, a jargon word is unavoidable; it may be the focus of your presentation. In that case, take care to define it more than once through the course of your presentation, and reinforce your teaching of the jargon word with context.

Acronyms and initialisms are a special class of jargon. It's easy to fall into a bad habit of using acronyms. They are often the most important nouns in your presentation. But unlike in a paper where you can define it, and people can look back if they forget what it means, there is no way to "look back" in a talk. I have attended many talks in which a TLA* is defined in the first moment, and if you miss it you are lost for the rest of the talk. Really, it often takes no more time to speak the words than to speak the letters.

(*TLA = Three Letter Acronym)

What do you want your audience to learn?

It amazes me that people prepare talks without ever asking themselves this question, but they appear to. A lot of people spend too much time describing their research methods -- what they did and what their data look like. It's easy to understand why people make that mistake. What you did is, after all, what you spent most of your time doing. But the whole point of your research effort was to learn something that you could then communicate to others. There's no need to force your audience to endure the same tedium. You can save your audience all that work by telling them what it was you learned.

Here's an exercise that I highly recommend: Compose a tweet summarizing your talk. It doesn't need to have perfect grammar, but it needs to be a sensible statement. In that limited space, you are not likely to say a whole lot about your methods! "I mapped clay minerals on Mars” describes what you did, but not why, or what you learned from it. "Large areas of Mars experienced rainfall over tens of thousands of years." Cool.

Make that tweet your conclusion slide. Make sure that your talk builds to that conclusion. How are you going to do that? Well....

What is your story?

It is impossible to overemphasize the importance of narrative in a talk. Standing up in front of an audience, you are telling a story in which you are the principal character. Stories are fun. If you tell a good story, you hook your audience, and then they will willingly follow you even into the dark corners of your subspecialty.

Stories are also functional, especially for people in the audience who may be struggling to follow you on that journey. If, for example, you have managed to tell your audience that this is a crime story, pretty much everybody in the room should be able to understand what the crime was at the beginning of your talk. Then, if you lose them while you're talking about evidence gathering, you still have a chance of picking them back up again when you tell them: that was the evidence, and this piece of evidence led me to the perpetrator. Even if an audience doesn't get spectroscopy or understand what a general circulation model is, they probably get how crime stories work.

Maybe you are not solving a mystery, but are instead an intrepid explorer who has gone to a place no one has gone before. Maybe you have fought a pitched battle with a legendary monster of a data set. (This is a great framework for a presentation about a null result; you get to be the tragic hero.)

Narrative is not just helpful to your audience; it's helpful to you, too. It provides a structure for your talk and helps you determine what is crucial to conveying your message and what is not. This is very important when you consider the following question:

How long do you have to speak?

You cannot say all the same things in a 15-minute talk slot as in a 1-hour colloquium. You just can't. Don't even try. However, you can tell the same story, which is why I put "story" before "time limit" in this blog post. Do you have a favorite novel that's been made into both a miniseries and a movie, and maybe even a 1-hour show? Think about the differences in story among these. As you go from longer to shorter versions, you see reductions in characters, in settings, in subplots, and finally, in the main plot line itself. Yet the story (usually) remains recognizable. Exactly the same process is necessary to go from a scientific paper to a colloquium to a long conference talk to a short conference talk.

It is especially important for very short talks to practice your talk and then, if it is too long, cut out information that is not needed to tell your story. Think of the poor audience, especially the undercaffeinated, the jet-lagged, the many people in our highly international community who are interpreting your spoken words as a second language. You cannot solve the problem of a too-long talk by talking faster. Simplify the story that you are trying to tell.

Some people solve the problem of a too-long talk by running over time. Do not do this. It is incredibly disrespectful to your audience.

If you talk through the time intended for discussion, the message to the audience is: I am here to talk to you, not hear from you. I do not care whether you understood my talk.

If you run into the next person's time, the message is worse: I believe myself to be more important than the next speaker. I also believe myself to be more important than the entire audience's opinion about which talk they intended to be watching during the time slot I am usurping.

It is only now, once you have identified your audience, your take-home message, and the shape of your story, that you should begin to think about making a PowerPoint presentation.

What visuals will serve to amplify your story?

I've observed that a lot of people use the phrase "prepare a talk" as though it is synonymous with "compose a PowerPoint presentation." Don't do that. The purpose of slides is to emphasize or amplify points that you, the speaker, are making with your voice and your body language. No matter what, your slides should serve to enhance your presentation, not to distract from it.

In fact, you should be capable of delivering your entire talk without any slides at all, because I promise you it will happen sooner or later that an A/V disaster will require you to. (I once gave a half-hour talk about amazing Solar System photos without being able to show a single photo.)

The number one error that almost everyone makes with PowerPoint presentations: There are too many words on your slides. People do this as insurance against forgetting their words, but it is bad for a conference presentation.

We use the same parts of our brains to process spoken language and written language. If you show me a slide containing more than a few words, I must choose between reading your slides and listening to you speak. I am physically incapable of doing both at the same time. Instead, I jump between reading some text and listening to some speech and then I miss things and I get lost. If your entire talk is written out on your slides, why the heck are you even talking to me? I read faster than I hear. You could just stand up there silently and advance your slides periodically. Instead, of course, what you do is turn your back to the audience in order to read your slides aloud, which is, again, an act of disrespect, even if you don’t intend it as such.

When I first wrote this article, I strongly advocated putting no words on slides. I still advocate that position for public talks. But commenters made several good points about why some words are useful, so I've adjusted my advice. Titles on slides are valuable as signposts through talks, especially for people who don't share your language. Writing out jargon or otherwise unfamiliar words helps you teach those words to your audience. In every case, though, the text on the slide should serve to emphasize or underline the points you make with your speech. They should enhance or clarify, not distract from, the words issuing from your mouth.

One advantage of having few words on slides is that if you find you have misjudged the pacing of your talk, it's not obvious to your audience when you are skipping material or slowing down in order to return to the right pace!

Graphs are a challenge in talks. Used well, they can make a scientific point clearly and succinctly. Used poorly, they can be a distraction. Graphs that are good for scientific papers are typically lousy for talks. It's not just a matter of font size and color. Good paper graphs have high information density, so throwing a fully developed graph on a slide is worse than presenting your audience with a paragraph of text. 

Sometimes, you don't need a visual to emphasize a point. In those cases, consider not having one. Put up a blank slide and watch the entire audience suddenly make eye contact with you. I like to put blank slides in places where I am making transitions in talks. It is a reminder to me to remind the audience where we came from and inform them where we are going. I can look them in the eye and check in with them to see if they are still with me, and let them know that the story is about to shift.

Your final slide is a special slide. It may be the one that the audience sees the longest. Do not have a slide that says only "Questions?" Instead, put your tweet-length conclusion on it. Write your name and some kind of contact information on it for the benefit of people who want to discuss your work with you. And then thank the audience for the gift of their attention, and invite them to ask questions.

Try to anticipate the questions your audience will have about your talk. You might have some backup slides prepared after your conclusion slide. This is a good place for the graph from your paper or to paste in some text on your methods because they may be useful tools in your response to a persnickety question. With a little luck, you can look like a genius for having just the right backup slide in your deck. If no one asks a question, one of these slides can serve as an opportunity to say just a little bit more about your work, or to advertise your collaborators' presentations.

Preparing to give your talk

Practice. I'm not just talking about practicing the specific talk. I mean, practice speaking about your science. Talk to your coworkers, your friends, your roommates, your family, your hairstylist, your cab driver. My plumber loves visiting my house because he loves to talk with me about space. Take advantage of any opportunity to speak to people about science. Practice is important because speaking is a different skill from writing.

Regardless of who is in your audience, you must use less jargon in a spoken talk than in a written paper. In a paper, if I come across a term whose meaning I don't recall, I can look it up. In a talk, I can't do that. The words you speak may not be as precise, but more people will understand your meaning, and remember, that's the goal.

Relatedly: Simplify your sentences. In a technical paper, a single sentence can span a whole paragraph. It's a way to armor sentences against criticism. But in speech, if I lose track of which statement your lengthy list of clauses is modifying, I lose the whole sentence. Complete a thought before moving to the next. Avoid passive voice. Give your sentences clear subjects, verbs, and objects. If a point is important, repeat it. Repetition is like verbal underlining.

If you tend to talk fast when you are nervous, then practice speaking more slowly and carefully, enunciating your words. Don't be afraid of silences -- you don’t need to fill every moment with sound.

Other random tips that didn't fit

Color blindness is more common than you might think. What this means: never, ever use a color spectrum to represent a continuously varying property. Vischeck is a super website to use to ascertain whether your graphics will be incomprehensible to the color-blind.

Your slides will almost certainly not be able to serve as a stand-alone record of your presentation. If your slides could stand alone, then your presence wouldn't be necessary. Regrettably, many institutions use PowerPoints as documents of record. For that, either prepare a second version of your slides that has the text you intend to say as fine print, or include your talk notes as a backup slide after the end of your presentation.

DO put your name on your slides. If you want people to be interested in your work beyond the few minutes of your talk, especially if you are a relatively obscure person in your field (say, a student), consider putting your name in the corner of every slide. If nothing else, make sure to put your name and contact information on your conclusion slide.

A word on the number of your slides. It's a commonly cited rule of thumb that you should have about one slide per minute. That assumes that people (or you) will be reading your slides. This one-per-minute rule of thumb doesn't work as well if your slides aren't word-heavy. And it makes the PowerPoint presentation drive your talk organization, rather than the other way around. So, I don't find that rule of thumb particularly useful. Focus, first, on what you want to say. Have slides at appropriate places to emphasize what you are saying. If you can't say what you need to say in your allotted time, you need to say less. Eliminate slides or slide content that are no longer needed to support what you are no longer saying.

A word on animations. If your presentation contains an animation (and they can be awesome visuals), make sure you have tested that your animation works. If you do not have an opportunity to test using the exact system that is employed in the conference hall, have a backup plan that does not involve berating the A/V setup. I like animated GIFs in PowerPoint presentations because they always seem to work. If you know you will have control of the clicker, an even easier way to do a not-very-many-frame animation is just to put one frame per slide and advance them manually. That will work even if your PowerPoint is turned into a PDF.

A word on anxiety about forgetting your talk. I think a lot of people write their entire talk on their slides because they're afraid they'll stand up in front of all of those people and forget what they want to say. I have a lousy memory and have no hope of memorizing an entire speech. Here's a method I use instead. I try to memorize the first sentence I intend to say about each slide or sequence of slides. When I advance the slide, I glance at it, and that triggers the sentence I intended to say when I advanced that slide. If I have words on slides, they are usually just titles; those titles also serve as cues to help me get my intended first sentence out.

How to be more expressive when you speak? If you're not naturally expressive, speaking at conferences isn't going to be good enough training. Try getting some experience elsewhere -- whatever suits you. Take an acting or improv class. Go out and speak to children. The younger the children, the more expressive you'll have to be to retain their interest. Volunteer to read to kids at a library.