I wish that more lecturers would consider returning to blackboards, instead of the lazy slides they currently do. It would both improve their talks and waste less of their prep time.

The nice thing about blackboards is that lecturers don’t try to write every word on a screen, but just talk as normal, only putting up explicitly technical content like diagrams and formulas. They can add or remove things from the board in response to audience feedback, and can improvise new ideas. Maybe most importantly, (sufficiently large) blackboards keep a large amount of context in view at any given time.

Blackboards are especially good as classroom tools because they are a fundamentally improvisational and accessible medium. You can’t prepare all the drawings in advance, which means that anything a lecturer can do on the board a student can in principle also do, and the form of the teacher’s lecture is a direct part of the pedagogy: the student can learn to imitate the same mode of thought with access to the same tools. There can be a drawing- and formula-based dialog between teacher and students in which they are all operating as equal peers, unlike powerpoint where one participant spent hours making a bunch of pretty graphs or typing up formulas in a cryptic markup language, and the other participant gets no insight whatsoever into how.

Making good use of computers would mean handing out interactive demonstrations with their full code available [code might be implemented in some drawing-based environment, not necessarily just lines of ASCII] at every lecture, and then showing how the code works and showing how to twiddle the parameters as part of the lecture, alongside the traditional writing-and-drawing-on-a-blackboard part of the lecture. Ideally students would have some way of also interacting with the same medium during class.

But making good interactive diagrams or writing code whose primary purpose is exposition takes 2 orders of magnitude more prep time than just throwing words and static diagrams up, and is just not feasible for individual lectures in a current education setup. Ideally we would have much better improvisational computer demonstration/diagram tools, but in practice the drawing tools we have are not really designed for a computer medium, and all pretty much suck. (If Bret Victor’s ideas from “Inventing on Principle” and “Stop Drawing Dead Fish” and “Drawing Dynamic Visualizations” were turned into polished, production-ready, mainstream tools, we might have a chance.)

I’ve seen some pretty effective lectures that were done live-coding style, e.g. in some notebook-based tool, but it depends on having the right topic for the lecture.