Why do people blow the punchline in scientitic 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.