On using slides for a lecture

Last evening I attended Pratap Bhanu Mehta’s New India Foundation lecture on the role of religion in politics in Modern India. It was a rather complex topic, with a lot of philosophical underpinnings, and as it happened, I soon lost track, and consequently interest, and so I ended up writing this blogpost as I sat in the audience.

Later, I was wondering what PBM could have done to communicate better and make his lecture more easily understood. Let’s assume here that PBM is an academic and so the last thing he would want to do is to “dumb down” the lecture (also my hypothesis is that he perhaps upped the academic quotient since the venue for the lecture was IISc but that’s just speculation and we’ll keep it aside). There is a certain way he is comfortable speaking in, weaving academic arguments, and let us assume that he is best talking that way, and it is not ideal to change that.

Imposing the above and any other reasonable constraints on what PBM would not change about the lecture, the question remains as to how he could have made it easier for the audience to follow him. And thinking about it in hindsight, the answer is rather obvious – visual aids such as slides (or even a blackboard).

The problem with the lecture was that given its complexity there were several threads of thought that the audience member had to keep track of as PBM built his argument. The flipside of this is that if you happened to miss a line of what PBM said, one important thread in the web would get lost, after which it would be extremely difficult to follow the rest of the lecture (This is perhaps what happened to me because of which I started blogging). To put it another way, the lecture as it happened required a high degree of concentration as well as maintenance of a reasonably sized cache in the minds of each audience member, which meant that the mental energy required to follow was really high.

In an unrelated conversation after the lecture, someone was talking about how the ancient Greeks reacted to the invention of writing with horror, saying that the human mind was perfectly capable of storing and transmitting information, and that writing would lead to a diminishing of human mental powers. As it turned out, writing helped free up memory space in human minds and that allowed for more complex thinking and a lot of subsequent scientific development. Of course cultures such as India’s which continued to insist on learning the scriptures by rote lost out a bit because considerable mental capacity continued to be used as a means of storage rather than for processing power.

So the idea is that when you have a complex talk that involves a complex web of thought, considerable mental energies of the audience goes into just maintaining a cache of all that you’ve said, and the arguments that you’ve constructed. And on top of that they need to continue to listen to you with concentration as you continue to weave the web. The rate of dropoff can be rather high. So the least you can do to help the audience ingest your lecture better is to help free up their cache, and putting out all the arguments spoken thus far on a screen, which means that their mental power can go into ingesting and digesting your new information rather than simply maintaining the cache. And that will improve your throughput!

So to generalise, use of visual aids (slides are preferable to blackboards since you don’t waste time writing, but if there isn’t much to be written blackboards will do, too, since slides might constrain) is a necessary condition to ensure high throughput when your talk involves a rather complex web of argument. It simply makes it easier for the audience to follow you and you can communicate better!

Of course if you are of the persuasion that there is a certain way you communicate which you’re unwilling to change and it is the audience which needs to make an effort to catch your pearls of wisdom, none of the above applies to you.