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February 3, 2013 / jpschimel

Why do people blow the punchline in scientific talks? The destructive effect of acknowledgements slides

Last words are our strongest. That’s why the punchline comes at the end of the joke and the conclusions at the end of a presentation. The conclusion slide is the “take home message” that we want our audience to soak up. So we should leave that message in front of them for as long as possible. Even while people are asking questions—let them stew on your conclusions.

But it has become common to end with an acknowledgements slide, usually that has a long list of funders, advisors, students who helped in the lab, etc. And since speakers are usually running out of time, they often skim over the list, almost dismissively, which does little to honor the contributors. In any case, to borrow a famous quote “Frankly my dear, I don’t give a damn.” What we want to learn from your talk is not your assistants’ names, but your science.

A final acknowledgements slide shuts off the conclusions before we’ve had a chance to assimilate them or to write them down—it undermines the message. That is shooting yourself in the foot, or maybe some part of your anatomy higher up and more vital.

The growth of acknowledgements slides is a Powerpoint effect. In the days of slide projectors, slides cost money so no one bothered with acknowledgements. But since images have become free, the tradition from papers of including acknowledgements percolated into presentations. But in a paper, acknowledgements are a postscript that readers can (and usually do) ignore. In a talk, there is no ignorable postscript—the last slide is part of the talk and should be reserved for your concluding take home message.

I argue therefore that you should generally skip an acknowledgements slide entirely. No one will really miss it. If you need to put agency logos somewhere to recognize funders, they comfortably go on the title slide or in the corners. If it is really essential to include acknowledgements in a presentation, either:

A) Make it the first slide following the title. Tell us who was important to the work before you begin the real story. This avoids disrupting the flow of the presentation and shows that recognizing these people is important to you, rather than being an afterthought. This is key in talks within your own Department (e.g. thesis defense seminars) when the people who helped will be in the audience and may actually care that they are recognized. It is also the most appropriate strategy when we give seminars at other Universities. As professors, our job is to produce both science and scientists; it’s our job to advance our students’ and postdocs’ careers and highlighting them for our colleagues is part of that. So highlight them—mention them first, and then weave their names into the talk as you present the strongest possible science story. For example “My student Jane Doe tested that hypothesis in an experiment that…” That’s a real acknowledgement.

B) Alternatively, show us the acknowledgements and then go back to the conclusions slide; leave that hanging on the screen while people ask questions and you discuss the work further. That gives them time to consider your conclusions and to absorb them.

My first principle of writing is that as an author it is your job to make the reader’s job easy. The same is true as a speaker. Help your audience assimilate your core message; that means giving them time with your conclusions. A second principle is to always think about what you are doing and why—does it advance the message? Or are you just doing it because you’ve seen other people do it and so it seems obligatory?

Don’t roll over your conclusions with an unnecessary and meaningless acknowledgements slide, or even worse, a throw-away “Questions?” slide. Your last slide is your take home message; use it for your most important message: your scientific conclusions.


Leave a Comment
  1. Jay T. Lennon / Feb 3 2013 6:28 pm

    Good points. I find that acknowledgements at the beginning of the talk disrupt the flow. When someone starts their talk, I’m ready for them to get into the questions; I’m eager to learn about the problem. So, I like your option B better.

  2. Michael J. Proulx (@MichaelProulx) / Feb 8 2013 1:35 pm

    Option A is best — they need acknowledgement (and jobs!) and this leaves the end of the talk pristine.

  3. Alex SL / Feb 8 2013 2:09 pm

    Your A and B are two good alternatives, but doing without the acknowledgements would be just impolite. Especially as long as everybody else has such a slide it will also strongly come across as impolite.

    Thinking about my field, I would however say that you may underestimate our researchers’ attention spans and overestimate the importance of the conclusions slide. The slide that needs to be on during the discussion is usually somewhere in the middle – a phylogenetic tree or ordination graph or whatever that presents the major results. The second to last slide may represent a few concluding bullet points, but that is not what people would want to discuss in my experience.

    And since speakers are usually running out of time

    Well, that’s their own incompetence and can be easily avoided.

    • jpschimel / Feb 8 2013 3:00 pm

      A talk is for the AUDIENCE. Every decision about how to structure it should be made with their needs first and foremost.

      Importantly, its not attention span that I’m concerned with but people’s ability to soak up complex thought as fast a speaker can deliver it. When someone runs through 3 or 4 final points, bing, bing, bing, and then flashes to the acknowledgements, the chances that someone in the room didn’t fully get all those points is very high. It’s not that I think they won’t remember their questions, but that they may have missed something. You need to give them time to assimilate the message. Maybe the critical image you want to leave them with is somewhere in the middle–so why not include it on that final slide so that the audience can stew on that?

      At a conference when you have a 15 minute slot, you don’t have much time so it’s important to use it as efficiently as possible to maximize the punch of the message. In an hour slot at a visiting seminar, you have more time to play with, but even there, I prefer to name the important people up front. Remember that in a movie, the front credits are for the important names. The final credits naming all the people who did anything roll when the movie is OVER and most people are walking out. That’s like the acknowledgements section in a paper. It’s an appendix. But there is no comparable “appendix time” in a talk. It’s not over until you step off the stage at the end of the questions.

      Beginning scientists, particularly, learn to do many things because they see others doing it without ever questioning whether it is a good idea. Traditions simply evolve. Most students I’ve ever spoken to about it never thought about why they end with an acknowledgements slide other than because they see others do it. When put to it, most agree that it makes more sense to end with the conclusions.

      • Alex SL / Feb 8 2013 9:49 pm

        A talk is for the AUDIENCE.

        Wow, I never even realized.

        More seriously, the audience may be made up of people who, if there is no acknowledgements slide in a culture where everybody else has one, will think, “didn’t even thank me for the samples I sent him, that [insult]; so much for future collaborations.”

        Again, I think that putting them onto the second slide makes sense and will take that into consideration for the next talk. But not having them at all is dickish, and people notice, especially if you are talking in front of a close-knit community of only ca. 120 researchers from the same field.

        I notice that once again half your comment implicitly treats poor organization of the talk and running out of time at its end as natural constants that a speaker is simply helpless to do anything about. Would it not be the most elegant solution to design the talk so that there is enough time for the major points to sink in before the last slide?

        And if we are talking about the usual 12 min talk + 3 min questions or 15 min talk + 5 min questions, the first step would be not having 3 or 4 final points, bing, bing, bing in the first place but only one or two. Squeezing too many messages into such a short presentation is setting it up for failure right from the start. Two days ago my student gave a talk in a symposium, and the first thing we did was leave out one of the two analyses she did so that it would not get too confusing.

  4. Thony Christie / Feb 8 2013 2:14 pm

    I take part every year in a series of public outreach lectures that have a whole series of promoters and sponsors. We always do the acknowledgements before the lecture even starts as a separate item. Functions well and disturbs nobody.

    • SpiralChaotic / Feb 8 2013 5:51 pm

      After reading the post, I was about to reply with exactly what Thony Christie said. Definitely want to end with the powerful high note; leave the behind-the-scenes stuff to paper or Web links.

  5. Ted C. MacRae / Feb 8 2013 3:37 pm

    I give a lot of presentations, often with contributors in the room. I do not use an acknowledgment slide, either at the beginning or the end, not only for the reasons mentioned but also because if you include one person then you have to include every person that ever touched the project in any way, shape or form, which serves to dilute the whole message of the acknowledgment slide. Instead, while the title slide is still up I give a verbal acknowledgment to those few people whose efforts were instrumental in the research presented – they thus become a part of the story with no interruption by a distracting extra slide.

  6. 4gravitonsandagradstudent / Feb 8 2013 3:42 pm

    As Alex pointed out, the issue with this idea is that the slide that is up during most of the questions period is _not_ the last slide: rather, it’s the slide that generates the most controversy or confusion. So that is the slide where the message of the talk should be centered. Unfortunately, that tends to vary based on the pet projects of the attending professors.

  7. Roz / Feb 8 2013 5:40 pm

    I agree that acknowledgements at the end are too distracting from the message. As an audience member, I immediately scan the list of names and want to check out all the people in lab photos (Do I know him? etc.)

    How about this for option C: giving acknowledgements throughout the talk, at the appropriate moment(s)… “and for this part of the project, X helped me with Y”. I think this is rarest, but I prefer it.

  8. nodders / Feb 8 2013 5:54 pm

    At conferences, I end my talk with “and above all, I would like to say thank you to the patients and volunteers who make our research possible and worthwhile. Thank you all”. With emphasis on “patients and volunteers” and “worthwhile” bits.
    I find that too often in medical research we (researchers) lose sight of what we really are striving for.

  9. katejeffery / Feb 9 2013 7:38 am

    This is a good article – it is true that conclusions need time to be digested.

    I’m not a big fan of acknowledgments at the start of a talk, because as Jay said, people want to dive into the material – and anyway they won’t remember who did what out of context. I’ve tried it once or twice and it always felt awkward.

    I know quite a lot of people who put names and a photograph alongside each piece of data they present, so that we know who did what as we go along, which I really like and would recommend. (I now put names, but not photographs, but may start doing so as it nicely personalizes the work). But that doesn’t allow for people who contributed other things than data, or other collaborators who have a more general connection to the lab but not that particular work.

    I’ve stopped reading through the list of acknowledgments as it wastes valuable time, which is why I like to leave that slide up at the end for assimilation. One possible compromise would be to present the conclusions down the left-hand side of the last slide and then add the contributors/funders etc on the right, leaving both sets of info available for digestion during questions. That would be quite cluttered though.

    Interesting issue! I hadn’t really given it enough thought, will do so now.

  10. namnezia / Feb 9 2013 9:42 am

    Skipping the acknowledgment slide is just plain arrogant and disrespectful of the folks who actually did (and paid for) the work.

    • jpschimel / Feb 9 2013 11:34 am

      I didn’t say that you shouldn’t honor the people who did or paid for the work. I said do it in a way that doesn’t diminish the impact of the work they supported. I am always very careful to ensure that I do honor my team–that’s why I put if first and weave their names into the talk. And I ensure that I maximize that honor by maximizing the message they worked to produce–which means using my last image that sits on the screen to reinforce the message.

      • namnezia / Feb 9 2013 1:25 pm

        “I argue therefore that you should generally skip an acknowledgements slide entirely. No one will really miss it.”

        This to me tells me that that would be your first inclination, unless you “have to” acknowledge funders, etc. See, our job as scientists is not just about the work, it is also about mentoring. And making sure that a particular finding or story is well associated with the grad student or postdoc, is going to be greatly beneficial to such people, especially if they are in the audience too, for example at a specialized scientific meeting.

        I agree that it is a good idea to put acknowledgments first, since you then have no chance of skipping them if you are rushing towards the end, and in general that’s what I’ve always done.

  11. Sarah Cornell / Feb 10 2013 10:30 am

    A very closely related issue is that a lot of speakers can’t keep to time… so leaving conclusions to the end is a very risky option!

    I put acknowledgements on the title slide – and completely agree that proper credit should be given to students/research assistants throughout a presentation, especially when they have produced a tangible piece of the story. Accountability matters in science, after all (which reminds me, look up Lance Kwok’s lovely article on “White Bulls” and academic parasitism…)

    I’ve taken to presenting conclusions – well, key message/s – right at the start, as well as at the end, especially in short talks. It is often easier as a listener to follow the building up of the the story when the foundations of the key messages have already been heard than to follow strands of narrative all the way through to a putative Ta-Da at the end. Especially if the science is complex (or the program is running late because earlier presenters tried to fit 15 detailed slides into 15 minutes).

    • jpschimel / Feb 10 2013 11:38 am

      An interesting approach to dealing with conclusions. I’ve seen it reasonably commonly in the biomedical literature, where papers often end the introduction with a short section “in this paper we show…”
      I think it is critical to recognize and advertise people who were important to the work, as you and others have pointed out. It is part of mentoring and advancing your people. But the way I’ve usually seen acknowledgements slides used, it doesn’t achieve that role.

      If something is important, then you need to take the time to do it right. If you’re not going to take the time to do it right, therefore it must not be important. If it’s not important, why do it at all?

    • Stella / Feb 11 2013 8:12 pm

      Yes! I have often thought having the conclusions at the start would be a far better way of doing talks. I am sick of this ‘murder mystery’ approach to talk structure – you don’t know if the results are actually interesting, so you don’t know what sort of attention you should pay to the methods. That and too many people spend too long on the introduction and methods, and too little time on the results. having the conclusions first would really change the whole feel of a talk.

  12. Craig Jones / Feb 13 2013 9:27 am

    I have never once cared to see or hear an acknowledgment slide in a talk and I have never once included it–either I have coauthors I list at the start on a title slide, or maybe there is some particular insight courtesy of somebody else whom I mention when I hit that insight, but it is like sitting through the credits at a movie without the possibility of a credit cookie or some interesting music. How many people do you find still in the movie theater at the very end even when there is this stuff? Scientific presentations are dull enough without deliberately taking the most boring parts of popular media and inserting them into talks.

    And I was taught from the very start of my career in earth science that a talk consists of three things: you tell the audience what you are about to tell them, then you tell them, and at the end you tell them what you told them. Even in 12 minute talks. Is this not common practice elsewhere? I get angry at a talk that doesn’t tell me why I should care, where we are going, and why we are following the route we are on to get there. At least tell me the mystery that is going to be solved if you feel that you can’t afford to ruin the theatrical moment at the end when you discover the Holy Grail….if I want a story where we don’t know where we are going when we start, I tune into Prairie Home Companion’s News from Lake Wobegone.

    Tell you what has gotten on my nerves lately: it is the proliferation of logos. I am half waiting for the cheerleaders to get everybody in a fever for Old State U’s science team to win that conference! We are a hairsbreadth away from ads in presentations (maybe you all in medically sponsored research are there already; I don’t go to your meetings). Must we know on EVERY slide that your university (or company) has one of the ugliest designs ever paid for by intelligent humans? One that clashes with the color scheme Microsoft suggested for you? Is there a big theft ring of slides where you need each slide fingerprinted so if it shows up elsewhere you can rise from the audience with a loud “AHA! Caught you, you intellectually deficient toad!”? Really? C’mon, everything you place on a slide should have a point and should inform the audience in the most effective way possible (which also means, please don’t read your slide to me). Anything that distracts is, well, a distraction and deflects attention from your message (unless your message is, wow, I mastered the “master slide” control in PowerPoint).

    I feel sorry for those of you who are crushed when not acknowledged in a slide. Is it really more important that you be acknowledged to a room full of people who really don’t care than to have the science that you helped foster be presented more thoroughly?

  13. Tony Hartshorn / Mar 5 2013 10:24 pm

    I buy your thesis. A related issue is just plain ol’ trying to cram too much in! Illustrated nicely here:

  14. ntthung / Oct 3 2017 8:59 am

    Dear Professor Schimel, there’s a typo in the title. I think you meant “scientific”. And many thanks for the post. Since reading it, I always end my talks with the Conclusion slide, and I do notice people reading it after I ended.


  1. Links 2/7/13 | Mike the Mad Biologist
  2. Why do people blow the punchline in scientitic talks? The destructive effect of acknowledgements slides | Watershed Hydrology Lab
  3. 2/15/13 Link Round-Up
  4. Where to put acknowledgement slides – Research Pointers
  5. 7 ineffective habits of scientists who communicate with public audiences – Denise Graveline

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