Tutorial 16: giving good talks, part 3: rehearsal

October 25, 2011

The best part of a month ago, we posted the first two articles in a series of four on giving good talks: part 1 on planning, and part 2 on preparing the actual slides.  Then we got distracted and posted a whole sequence of articles on Open Access ([1], [2], [3], [4], [5], [6]).  If that seems like an intimidating sequence to catch up, you should just read the last one, which shows that the money Elsevier alone takes out of academia is enough to fund every research article in every field in the world as open access at PLoS ONE’s rate.

We now return you to your regularly scheduled programming.

If you followed the advice in the first part of this series, your talk has a clear story that it means to tell, and your slides illustrate the story with maximum clarity.  As you’ve been assembling the slides, you’ve also been figuring out what you want to actually say.  So are you ready to give the talk now?

Not if you want it to be the best it can be.  And why wouldn’t you?

A few years ago, when I was still a student, I was talking with a well established and respected professional about preparing talks.  He was very casual about it.  “That’s one of the big differences between an old pro and a student”, he told me.  “Students take a long time over preparing their talks, but the pros just throw it together on the plane on the way over.”  I nodded and smiled politely; and said to myself, “so that’s why students’ talks are usually better.”

So why do you need to rehearse your talk?

1. Fitting into the time

One of the most unprofessional things you can do is run over your time-slot.  If you do this, then you’d better hope you have a good session moderator, who will cut you off dead.  The alternative is that all the people who are scheduled to follow you in that session will hate you forever, for eating into their time.

You also don’t want to fall short of filling your time — it’s rarer, but I’ve seen it done that someone gives a talk that takes maybe eleven minutes, and then has to squirm at the podium taking a sequence of increasingly irrelevant questions for nine minutes.

You want to aim to come in about a minute before the end of your slot, maybe two minutes max.  That allows time for a couple of questions; or in emergencies, allows you a little bit of slop, in case you misjudge your pace.

With experience it becomes possible to estimate roughly how long your talk is going to take just from the slides.  But you never really know until you actually give it.  It doesn’t matter if you’re a grad student giving your first talk, an established researcher, or an emeritus professor: be a pro, rehearse your talk, and hit your mark.

2. Becoming fluent in delivery

A simple one.  You don’t want to be one of those speakers who keeps having to stop and think “Now what was I going to say next?” or “Why did I put that slide in again?”  You want to talk clearly, confidently and fluently.  How does that happen?  Practice!

3. Maintaining flow and momentum

This isn’t the same thing as mere fluency.  That’s about how you speak, but this is about what you’re going to say.  You already know the Big Picture of the story you’re going to tell from way back in the planning stage, and you know much of the detail because it’s in the slides.  But you will never know how well it works until you actually give the talk.  In my experience there is always something that needs changing to keep the story moving, and to keep it engaging.

It may be that I start talking about the perforated anterior centroparapophyseal laminae of Giraffatitan without having said what a centroparapophyseal lamina is.  I need another slide showing what this is.

Or it may be that some slides I have later in my talk need to be pulled up closer to the front, because they lay out background information.

Or, conversely, I have a sequence of slides near the start of the talk that don’t really follow from what preceded them or lead into what follows; but they make sense when I shift them further back in the talk.

It’s amazing how often it is that you only find these problems by actually running the talk.  No amount of paging through the slides and frowning thoughtfully will reveal these structural gaffes.  You need to actually use the slides, in the context of giving a talk, to see where the structure is off.

In fact, it can be useful to think in terms of building two talks. When you make the slides, you’re really piling up raw material, which will hopefully be close to everything you’ll end up needing, but will almost certainly not be an exact fit. It’s often necessary to rebuild the talk to some extent during rehearsal, as you learn by experience what you don’t need, what you do, and what order it should come in.  The talk you end up with, even if it uses nearly all the same material, can be different in fundamental ways from the one you started with.

4. Deciding what to cut

This is a special case of  maintaining flow, but I want to treat is separately because it’s so painful to do.

I hate cutting slides that I have expended valuable effort on.  But I end up doing it in nearly every talk that I give.  It’s not that there’s anything wrong with the slides: they just don’t fit the flow of the talk.  Maybe they’re off on a tangent that isn’t in the direction you need to go; sometimes they are just redundant.

In my last talk, I had a sequence of slides showing that the sequence of cervicals in the AMNH Camarasaurus specimens were not complete or articulated or even necessarily each from a single animal.  They were beautiful slides, including cleaned up plates from Osborn and Mook 1921, the single greatest ever publication on sauropods.  But when I ran the talk, it was apparent that they just weren’t necessary.  They followed slides when I showed that the necks of Giraffatitan HMN SII, Apatosaurus louisae CM 3018 and and Mamenchisaurus hochuanensis CCG V 20401 were incomplete, disarticulated or distorted.  If I’d then gone on to do the same for Camarasaurus, the audience would have been saying “All right, we get it already, can we move on now?”

So I cut the slides.  It hurt to do it.  But it made a better talk.

Pro tip: it’s easier to make too many slides, and decide what to cut after a rehearsal run or two, than to make too few slides, come in short, and have to pad things out. And when you cut slides, don’t actually delete them out of the presentation file. Move them to the very end, after your conclusion and acknowledgment slides. That serves two purposes: first, those slides are still around in case you decide later you need them back in the talk (because you ditched something else, for example), and second, it’s worth leaving them even in the final version, because they might come in handy during the post-talk Q&A. Sometimes you only have room to discuss n points in the talk, and if point n+1 is covered in a post-conclusion slide and someone in the audience fortuitously sets you up to talk about that with their question, you can sneak a little more presenting into the Q&A time (don’t force it though).

5. Getting feedback

So far I’ve not said who to rehearse your talk to.  For much of what I’ve discussed above, it suffices to run it on your own, with only a stopwatch for company.  That can help you with timing, fluency and flow.

But it’s not really a talk until you give it to someone.  So I strongly encourage you to find a victim, and deliver the talk exactly as you will at the conference.  Get your victim to make notes as you speak, then go through them afterwards.  (Do not stop to discuss as you’re giving the talk: not only will it mess up the timings, it will break the flow that you’re trying to understand.)

There are plenty of reasons to do this.

  • The pace of your delivery will be different when you are talking to a real human being.
  • Speaking with an audience will show you whether you truly know the material well enough to cruise confidently through it.
  • Someone who is new to the material will spot flaws that you have become overfamiliar with and can’t see any more.
  • Someone who doesn’t know the material as well as you do will go “huh?” when you suddenly start talking about centroparapophyseal laminae without so much as a by-your-leave.

In a completely ideal world, you’d run the talk on your own, then with a fellow expert in your own field, and finally with an intelligent layman — either someone who works in a different subfield, or perhaps a different field altogether.  That’s how you discover whether you’ve included the right background information for non-specialists to follow your argument.

Do all this, make the relevant tweaks to your slides, and you will — finally! — be ready to actually deliver the talk at the conference.  We’ll discuss that next time.

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10 Responses to “Tutorial 16: giving good talks, part 3: rehearsal”

  1. Albertonykus Says:

    Extremely useful and informative post, but I have to add that the salmon makes me hungry.


  2. Very very smart, very good – but for people like me just utterly useless: my talks are NEVER finished, often not even started, before I have left home :( I know, I need to change that, you can’t be a student or young post-doc researcher and behave like a bored old prof. Still, so far I have survived ;)

  3. Michael Richmond Says:

    Thanks for providing so many good pieces of advice!

    Let me add one item that comes AFTER the talk is over: please make your presentation available on a website somewhere. Not everyone who is interested in the subject was at that meeting. If you convert the presentation to PDF, it will be more widely available.

  4. Mark Witton Says:

    Excellent series of tutorials. I often refer students to SV-POW! for its various ‘How to…’ guides for writing and presenting, not to mention learning a thing or two from them myself. Long may they continue.

  5. Don Cox Says:

    A trial run given to a one-person audience will not be an accurate guide to timing, because you need to speak more slowly to a full audience, with longer pauses.
    I find a PDF file is better for delivery than Power Point. Every computer has the PDF reader on it, and it avoids the temptation to use bullet points.

    Bullet points are soporific.

  6. Mike Taylor Says:

    Don, what you say about timing makes sense; all I can tell you is that it doesn’t match my experience. I’ve found that when I give my talks to an audience, they take the same time they do when I give them to a single person in rehearsal.

    Does every computer really have a PDF reader? I wouldn’t want to bet my whole talk on that, especially when I know the presentation computer has PowerPoint, because everyone else is using it. Its safest to be in the mainstream when technology is concerned and time is short!

    No argument on bullet points, though :-) I think they do have a place, but that place is only in a brief summary of points that have already been made in individual slides — for example, in a Conclusions slide at the very end.


  7. […] have clear slides with striking, relevant images and no visual distractions; and you should have rehearsed your talk so that it’s clear and coherent, and fits into the time available with a minute or two […]


  8. […] that’s it — how to make good slides.  Next time we’ll look at rehearsing the talk.  (It’ll be a much shorter post than this one.) Share this:FacebookRedditTwitterLike […]


  9. […] Also: several times as I watched Graeme’s talk, I internally raised an objection (such as low explanation-of-variation values of PC1 and PC2 in the plots he was showing) only for him to immediately go on to note the issue, and then explain how he deals with it. This should not be too difficult to emulate: anticipate possible objections and meet them in advance. This is something to have in mind when rehearsing your talk. […]


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