Learning how to give talks
The current two weeks, 80% of my working hours consist of participating in courses on how to teach. The courses include three days on "teaching in higher education", which covers several aspects of teaching, including giving lectures---and a "Master class" on "presenting with theatre skills". Both are a nice surprise.
I did not expect the courses to be bad, but I was prepared for the worst. What I learnt from the presentation courses I had to take as a student, was that "slides" were holy. Lectures with teachers writing on the blackboard I learnt to associate with complex derivations I never bothered to follow and could better check out later at home. As students we learnt to give smooth overhead or beamer presentations, to which we talked.
I will refrain from discussing now whether the above approach was a good way to get started. Maybe it was. However, in the past years I got convinced more and more that it is not a good way to continue.
An eye-opener for me were Erik Demaine's lectures in the Aarhus Summer School on Massive Data Sets. I can still picture him drawing on the blackboard how to lay-out a tree in memory for optimal cache performance. The nice thing about a good "blackboard talk" is that it is much easier to follow what is happening. You are with the speaker when he writes or draws things on the board. Slides and computer presentations, on the other hand, often contain too much information and the speaker hardly gives you any time to discover the nice bits of information and explanation hidden in the slides.
Another eye-opener was the seminar on approximation algorithms organized by Alexander Wolff for a dozen students in Karlsruhe. The students showed a variety of approaches to giving a talk. Talks given with overhead transparencies or a computer presentation tended to be average; talks with the blackboard tended to be either very good or very bad (the bad student used the blackboard because he "did not have time to prepare slides", read: "did not take time to master the material"). I prepared my own presentation late, during and between the first day's talks, and could thus draw inspiration from the students' blackboard talks while making my computer presentation. The audience was impressed by the way I organized information on the screen.
I was afraid that the course on teaching in higher education would try to convert me back to the powerpoint doctrine: someone must have made that up, it must be the educationalists. Not so. No powerpoint doctrine. It was not them, and the teachers are very well aware of the strengths and weaknesses of the various media one can use. Nevertheless, what they can still teach me about how to give a talk is mostly polishing.
But the Master class provides some insights that are really new to me. To start with, we got explained two models of giving a talk: the clew model and the onion model.
The clew is a logical, linear argument building up to a conclusion at the end of the talk, like a clew unwinding until you finally come to the core. Miss one step in the talk and you lose the plot and miss the point. And yes indeed, this is exactly what happens when I listen to most conference talks and some lectures. In a three days' conference, I actually follow the first five minutes of one or two dozen talks. That is more or less it. After those five minutes, I get lost. I miss a "slide" because I am still thinking about the previous one, get distracted by some random personal associations I had with something the speaker said, or simply doze off because the speaker has a tiring accent.
The onion talk starts with the main message, and adds depth in successive layers around it, always returning to the main message between layers. Since the main message and the main ideas are repeated often, a listener can still follow most of the talk even after dozing off for a minute. Also the talk does not get screwed up near the end when the speaker is running out of time, because by then, the most important things have been said already and the speaker has no reason to hurry.
This is an interesting way to look at it, not only for lectures but also for conference talks. Until recently, I was already prepared to accept that people do not have to remember anything from a conference talk except that they have to remember the speaker or the topic well enough that they may read the paper. This can be achieved in five minutes, so what do we use the other fifteen minutes of a typical conference talk for? We typically use it to explain too much in too little time---all doomed to be forgotten.
I will keep that onion in mind while preparing my next conference talk. I will give one or two talks at the upcoming ISAAC in China, so there you may hear to what extent I decided to go onion and whether it works or not.
So what about the theatre skills, you may ask? Well, this is all so new to me that I will refrain from posting commentaries here. I can confirm though that it is very interesting---and confronting---to have someone look at your expression and relation with the audience instead of just seeing to it that you present a knot-free clew with legible slides. It is too early to tell if I, that is my audience, will actually benefit from it.