In a math talk, is it better to display the number of slides left?

Question

In a math talk (at a seminar or a conference, not teaching) that uses projected slides, is it better to display the number of slides left or not? What are the pros and cons? Some people tell me they like it, others prefer when it doesn't appear. I'd like to have some objective comments about this.

For some context, talks in math are typically one hour long, so the number of slides can be large. I like to cut talks into a few short sections. Right now I'm using the following layout, displayed at the top of every slide (from the "Frankfurt" beamer theme):

The current slide in the current section is highlighted, as well as the title of the current section.

Answer 1

Halmos advises that in preparing a talk you should have a block of material that you can omit if you are running short of time. But if the slides show number of pages left, you cannot do that invisibly. For example: in an hour lecture, if you are 5 minutes from the end of the hour, but your numbering shows you are only halfway through your slides, the audience will be getting restless.

Answer 2

A method to please both probably exists. Just tug a #/## at the lower corner, with the first number being the current slide number and the second one being the total slide number. People who have question on a certain slide can jot down the number quickly and come back (rather than "Can you go back to the third dot under 'The Model?'"); people who find a large bar intrusive will be less likely bothered by some small numbers at the corner.

I personally don't have problem with how beamer displays the time-line; it looks elegant. (I sometimes use it just to be that "lone kid in the department who uses LaTeX.") However, it requires some skills to be truly effective. Too many times I have seen very long section names used in this device, which clutter up the time-line badly.

And to be honest, I'd rather save the area on the slide to arrange information beautifully for those who pay attention then to give up 10-20% to set up a device for those who doze off and want to hop back in. Even I do care about them, major section signposts do not need to be on the screen all the time, the speaker (or a transition slide, or a small phrase next to the #/## index) can also deliver the transition.

Disclaimer: I don't give math talks, I work in biomedical field.

Answer 3

I would always use a

current page/last page

setting. Additionally, you should have an outline of the talk the help the audience to navigate through your talk (but not to spend five minutes of the talk to read out your outline).

This helps the audience to keep track of where they are, and also help the chairperson of the session to see where you are going with your talk. When I am a chairman, I usually get nervous when a speaker has no outline and no page numbers and his time is running short. I then keep asking myself, when I should interrupt the speaker and it usually turns out for the worse of the speaker…

But you need to keep a few things in mind:

• The number last page should really be the number of the page that you want to display last. If you have any back-up slides after that, insert the correct number manually, e.g. by \renewcommand{\inserttotalframenumber}{22}. You may or may not restart the frame counter after that last official slide.

• Make sure that each counted frame/page is really one page. I've seen a talk that had ~100 "official frames" but more than 80 of them showed a single image that was part of a movie.

• Train you talk such that you don't have to omit something. It's a matter of preparation and can be done. Put in time, effort and also practice your talk to get the right timing. While you plan, keep in mind that you may have questions during the talk.

Answer 4

I would omit the slide count altogether; what is important is which topics you have covered and have yet to cover. For example, you might periodically show a slide that looks something like

x Topic 1
x Topic 2
  x Topic 2a
  * Topic 2b
* Topic 3

at which point you would indicate that you have completed talking about Topic 2a and will proceed to discuss Topic 2b. The fact that Topic 1 was already covered, and that Topic 3 is still to come, is implied.

Your audience already knows how much time you have been allotted for the entire talk; they don't need constant reminders about how much longer you will be talking. The purpose of the topic lists is not to let them know how much longer you will be talking, but to remind them how each section of your talk fits into the whole.

The point @Penguin_Knight raises about the slide numbers providing a point of reference for a question is valid. You can provide a slide number, though, without providing a slide count.

Answer 5

tl;dr: Show it. In the beginning, the audience will be "warned" if your slide cadence will be fast or relaxed. And both you and audience will know how fast your progress is. If you have two slides pending chairmen are usually well-disposed when you are running short on time. If they don't know they will more likely interrupt you and ask you for speeding up. If you add extra slides for discussion - tables, reference citations, more details, etc. do not count them to the pages counter. It is awkward to have "Thank you" slide with number 10/15.

For short talks (10-20 min) I ommit the outline part, because it is always Introduction - Experimental - Results - Conclusion setup. I believe that every field has its "typical pattern". And it also cost time I would like to spend elsewhere (Results).

I have modified the crane layout. Above the header there is the title of the speech and in the footer there is my affiliation, conference name and date and the page numbering.

For longer talks (>30 min) like plenary lectures, I would divide the talk into parts and adress them in outline. In that case I would also show th page numbering (page/pages) and small "progress bar".

Regarding GEdgar's point, having half of the slides pending when having 5 minutes left during 1 hour lecture is utterly poor timing and displaying page numbering is of lesser issue.

Answer 6

In general user experience (human computer interaction, human factors, psychology) research, progress indicators are to let people know how long they need to wait or work to get a job done, and to allow them to determine if something has gone wrong, or if they thus need to conduct themselves differently (speed up, slow down). You already have a natural progress indicator built into your talk: the time. If your talk is one hour and there is 30 minutes left, the audience need only check the clock to see just how close you are to being done. The concern would be if you are suddenly going to be done early (and I don't recall ever being worried that any speaker was going to finish talking too soon), or too late (a very real concern), so a progress indicator would really only be useful to determine "on time, going over time, will finish early".

There is a second type of progress indicator available to you during a talk, which is...well, you. You can simply say things like "let me check the time...ah yes, we are right on schedule!", or "in the interests of time I'll omit some less interesting details here...", etc. You are providing the audience useful information they want to know, namely "will I need to prepare to walk out on this joker while he is still talking to get to the next talk on time", or at worst "can I possibly survive until the end of this talk...". Again, the time is the natural progress indicator here, so everything is likely to be judged relative to that.

In your proposed method of slide progress indicator, my question would be "what does this progress indicator add that the time and you as the speaker are not already providing?" What does your system provide to the audience, which they can not already determine trivially by context?

Other things your system could do is serve as a kind of mental map, allowing the audience to see how what you are saying fits into the talk as a whole. In most academic talks I'm use to, this is already provided both by the introduction/overview and the natural structure of talks. Unlike in website navigation, it is not assumed that your audience will get mentally lost, such as by getting up and walking off to get lunch and then expecting to pick up from where they left off (a big reason for such a progress indicator on a web presentation/form).

The biggest use I can imagine in this is actually not for the audience, but for you the presenter. At a glance you can see how you are pacing each section, and with some previously calculated mental math you can see if you need to speed up or slow down. The status indicator can also serve as a reminder to you of what is next, which can help you talk about the right thing at the right time and segway smoothly into the next slide and section. I know I personally regularly rearrange my talks as I revise them, and its easy to remember the order of the slides as it originally was and forget your last revision.

So in the end, based on my understanding of related research domains and personal experience giving talks and listening to them, I don't think the progress indicator of slides left/slide numbers is going to be a significant benefit to your audience. However, I do see how the system might be useful to you, and if it helps you give a better, more organized, more confident, smooth, useful talk, then that is of tremendous benefit to your audience indirectly and you should go for it! So long as you don't provide false indication, such as making it seem like you are going way too fast or too slow to make appropriate use of your time slot, then I don't think there is any real concern in choosing the system if you feel it helps you.

Answer 7

Would you like, in an exciting movie, to have a counter at the bottom of the screen, saying: "50 out of 90 minutes"? There may be movies that profit from this as a suspense build-up, but most of the time, this would be quite a distractor and very counterproductive.

No, tell a good story, build suspense, and develop your argument stringently, don't bore your audience with structure which may make sense post-hoc, but not pre-hoc. Ideally, make them ache for the next slide.

Of course, you yourself should ensure to be well on time, though, but take care of not turning this into the worry of your audience.

And, if you conclude a few minutes before the expected time, when expectation is still high, and people have not yet remembered to look at their watches, you've done it the right way (TM).

Answer 8

Part of a good talk is good time management. If you have prepared well, including trying out your talk before it gets serious, you should have a good idea of how much time you will need and can adjust accordingly. You will even be able to get an idea how long you can engage with audience comments and questions. For the purpose of this answer, I will assume that your time management is good. If itisn't, you might as well just inslt your audience by swearing at them.

If your time management is spot on, you have two reasons for why you might want to display the number of slides left.

1. You may want to make it easier for the audience to refer to some slide of yours. In that case, precise slide titles will serve this function better. I think it is easier to ask for the slide that gives the equivalents of the definition of a woolladuh than asking for slide 7.

2. You may want to signal that our talk is on time. I think this is indeed legitimate in many contexts. In a conference where only short presentations are allowed, worrying that the speaker before you steals all your time might prevent you from paying attention. In a setting where people running out of time is a real possibility, I think the (number of current slide)/(number of total slides) works well, it gives the relevant information while minimizing the increase in noise. For a long seminar presentation, providing a roadmap of your talk will do more to ease your audience.

Answer 9

I would not display number of slides left when a) you have good reputation or goodwill with an audience (very interesting topic, you have been invited, people already heard your other talks) or b) your presentation will be approximately at a constant pace.

However, I would display number of slides left, if you are c) in the environment where many people (try to) go over their allocated time (e.g. conference) or if d) you have a slide for which you know will spend disproportionate amount of time on. But d) is best handled otherwise (e.g. split it into multiple slides), as you may get the opposite effect, depending where in the presentation such slide stands.

Number of slides left is to assure the auditorium "I know what I am doing, bear with me, I am aware of the time constraints", and if you then go over your allotted time it will look a bit silly.