A verbal presentation of science is a fundamentally different beast than a scientific paper. Many of the things that make talks boring are elements that are transferred directly from the written papers. It is extraordinarily tempting, I know, to give a talk in which you recapitulate every experiment that you have done, with all of the controls, to convince your audience that the exciting results you are presenting represent a fundamental advance in the field. Certainly, the aficionados in the audience will appreciate your rigor. But, of course, they probably won't entirely believe you until they read the paper anyway. The big problem is that dragging the audience through the thicket of your experiments will very likely put most of your audience to sleep. To engage the widest possible audience, you must make a tradeoff between breadth and depth of presentation. Usually, breadth is better than depth. The aficionados will understand that you are trying to reach a broad audience and, because you have obviously energized the room, they will look forward even more to reading your paper. The non-aficionados will be thrilled to learn about something so interesting that they had not heard before. You will have begun their engagement in a conversation on the topic that will continue in the question-and-answer session and, hopefully, far into the future.
So, how, exactly, do you convert your great scientific paper into a talk? I will discuss several specific issues in future posts. For now, I will focus on the overall structure of the talk. Below, I provide an outline to one approach to an effective structure. There are probably an infinite number of effective structures. I recently heard a brilliant talk by a student who seemed to break all the rules by showing us data and then saying, "Now, let's just ignore that finding for a while. We'll come back to it." She had us on the edges of our seats for the whole talk and the denouement was in fact very satisfying. So, my advice is meant only to get your creative juices flowing so that you can find a talk structure that works well for you. The overall goal is to keep the audience intrigued and, dare I say, entertained.
First, you will keep or lose your audience in the first few minutes. Remember, they are on your side, at least at first. So, take their goodwill and run with it. Make it clear from the very beginning what the problem is and how cool you think it is. This may require backing up a bit from the specific topic of your paper. Not everyone is going to immediately think that studying a few cells in the cockroach mushroom body is the coolest project ever, so give them something to grab on to. In plain language, talk about the general nature of the problem. Talk about how, for example, animals learn by associating different sensory experiences and that it is important to identify and understand the anatomical basis for this learning. But, make it specific, make it palpable. Talk about how cockroaches learn to associate your footfall with danger and to skitter into the wallboards when they hear you coming.
Then, with your audience attuned to the fact that you are discussing an interesting problem, feel free to proceed quickly to something specific about your project. Why the cockroach? Why the mushroom body? Why these cells? Use photos or illustrations or movies to rapidly orient your audience to the nature of the problem and the specific aspects you have studied. Don't put words on these slides, other than labels. I discuss this in further detail in Principle 1: Don't Put Words on Slides. Guide your audience through the images. Point to specific places in the illustration when you discuss this thing or that thing. Don't rush through these introductory slides (or any slides). Allow the audience to absorb the complexity of the images you are presenting and to accept your guided tour of the most important aspects for this presentation. Do not overwhelm them, but introduce them to the richness of the problem you have studied.
Now, start revealing your methods and experiments. This is the most important point where you must strike a balance between breadth and depth. You want to provide sufficient information to demonstrate that you have performed your work carefully and that your experiments are sensible, but you don't want to drown your audience in details of your experimental methods. You can say "We generated transgenic Drosophila" without providing details of the injection protocol, the transgene structure, or the landing sites used (unless, of course, your talk is actually about new methodology related to transgenesis). This will take some practice, but when you are using widely-used methodology you can usually assume that your audience will believe that you used appropriate methods with appropriate controls. They can read your paper for the details if they are interested.
It is rarely helpful to present all of your experiments. The best papers include multiple experiments, probing the problem from orthogonal directions, to demonstrate that a result is true. In a talk, that is not always necessary. If you are presenting a mind-blowing, non-intuitive result, then it is probably critical for you to present each of the experiments that supports the view that this result is correct. But, most scientific results are not mind-blowing and non-intuitive. Mostly, they are incremental. (In a good way! Science is mostly incremental.) The results often make a lot of sense given what we know already. If you are giving one of these talks, then you probably don't need to present every experiment and every control that you performed that led you to your conclusions. Instead, focus on the most compelling results. Tell the audience in some detail and with care the killer experiment that really proved the point. You can also tell the audience "There are several other experiments that support this view, but given the limited time, I will not discuss them today. If you are interested, I am happy to discuss them with you later." Then, they know that there are other results that support your conclusion and that you are not trying to hide anything. This allows the audience to focus on the key messages in your talk.
It is commonly suggested that speakers should "Tell the audience what you plan to tell them, then tell them, then tell them what you told them." I agree, but only in the broadest terms, not in the specifics. I do not think it is useful to provide the audience with a laundry list of the what you plan to tell them. (And never use a bullet point slide for this!) Instead, get them excited about what you are going to tell them by igniting their curiosity about the problem, just as your curiosity drove you to do the project. Then, when you are actually telling them about experiments, feel free to tell them the same thing in multiple ways. Maybe once in plain language, and then once in more technical language. Don't repeat yourself verbatim, but find multiple ways of explaining each result. Finally, as you wrap up the talk you have two choices. If you have performed a suitable job of engaging your audience, it is unlikely that a formal conclusion will be necessary. Everyone will understand precisely what you did and why you did it. In this case, you won't need to "Tell them what you told them." However, if you feel uncertain about this, then you should feel free to remind the audience of what you presented. Remind them of the problem and the approach you took. And point out how your results have contributed to our understanding or helped to solve the problem.
Now, a few words about slide content. Please, I really beg of you, do not present the figures from your paper directly in the talk. First, delete the figure panel labels (a, b, c, etc.). These panel labels do not communicate any useful information to the audience. More importantly, figure panels from papers are usually relatively small and the full figure can be complex, with many experiments presented in a single figure. You are likely simply going to confuse the audience by presenting many panels from a single figure in a single slide. In a talk, however, you are not constrained to showing small images because you can show multiple panels consecutively, rather than simultaneously. Show your beautiful experimental results in all their glory in images as large as possible. Allow the audience to really absorb these data. Allow them to, effectively, "interact" with the data and to come to their own conclusions about the data as you guide them through the results.
Try this exercise. Cut all slides except those that illustrate data, preferably the results from key experiments. Then, working from that skeleton, be extremely critical about whether a new slide really adds value that is better communicated with the slide than with your voice. Hopefully you will find that you are left with only images or movies that communicate information more efficiently than your voice.
Then, for the talk itself, just stand, face your audience, and speak. Introduce your topic. Show slides when they communicate information more efficiently than your words can. And engage with the audience. Talk to them like you really want them to understand what you are saying. DO NOT talk to the slides, or even half-way to the slides. Face and talk to the people who came to hear you. Practice this. Practice it again. Keep practicing until it feels comfortable. I routinely practice talks, even talks that I have given previously, two or three times in the days leading up to a presentation. There is no such thing as too much practice. I was going to reserve a whole blog entry for the Principle "Practice, Practice, Practice." But maybe you get the point.
I am often asked how much detail should be provided in a talk. Younger speakers are often understandably nervous about not presenting their experiments in full, lest the audience think that they are not rigorous scientists. My usual advice is that you should aim to lose most of the audience on occasion, as you delve into the details of an experiment, but then rapidly pivot back to a more general conclusion that can be understood by everyone. If you drag your talk into the morass of details surrounding your experiments and you don't return, then you can be assured that most people in the room will not follow you. If they are generous, they will think you are a great scientist. More likely, they will think the talk is boring. Picture your talk like the silhouette of a very peaked mountain range rising from and then descending into the plains. Start very general, then ratchet up the details until you hit a peak of an elegant experiment. Very rapidly summarize this result for a more general audience. Then, you are free for an ascent up another peak. Of course, it is ideal if you can always use plain language, with minimal jargon, even when you are explaining your most sophisticated experiments. (Most talks abound in jargon. So you must examine your language very carefully to minimize the jargon.) The audience will not think you are dumb for using plain language. They will think you are brilliant for explaining such complicated work with such straightforward language. The ability to explain the most complex problem in the plainest of language is a sign of true understanding.