20 August 2009

A Nobel prize winner’s view on slides versus ‘chalk and talk’

One of the best things I’ve ever read on presenting complicated technical material to audiences is an anthology published by the Royal Institution that was taken from the writings of Michael Faraday (19th century pioneer of magnetism and electricity) and Lawrence Bragg (20th century Nobel prize winner).

Both of them were famous for their ability to take audiences, whether lay or professional, to the frontiers of science.

Writing decades before the invention of PowerPoint, Bragg had this to say about slides and ‘chalk and talk’ (which isn't a million miles away from some of the points in my last three posts on the subject):

'Lecturers love slides, and in a game of associations the word 'lecture' would almost always evoke the reply 'slide'. But I think we ought to apply to slides the same test, 'What will the audience remember?'

'Some information can only be conveyed as slides, photographs, or records of actual events, such as the movement of a recording instrument, for instance, a seismograph. But slides of graphs or tables of figures are in general out of place in a lecture, or, at any rate, should be used most sparingly, just because the audience has not time to absorb them.

'If the lecturer wishes to illustrate a point with a graph, it is much better to draw it, or perhaps clamp the component parts on a magnetic board or employ some device of that kind.

'I remember well the first time I was impressed by this latter device, during a lecture on airflow through turbine blades. The lecturer altered the angle of incidence and the air arrows by shifting the parts on the board.

'It is again a question of tempo – the audience can follow at about the rate one can draw (my emphasis); one is forced to be simple, and the slight expertise of the drawing holds attention. One must constantly think of what will be retained in the audience’s memory, not of what can be crammed into the lecture.'

(From Advice to Lecturers: An anthology taken from the writings of Michael Faraday & Lawrence Bragg, London: The Royal Institution of Great Britain, 1974, ISBN 07201 04467),


pintosal said...

In my latter years at school I went to a Royal Institution Christmas Lecture. This being the early 1960s, 'slides' were the things that caused tears in my trousers, and only later did I associate slides with 35mm transparencies.
I digress ...
This 1962 lecture by R.E.D. Bishop was entitled "Vibration". It was full of illustrations of various scientific phenomena, presented in an engaging way that young minds could grasp.
The most vivid image for me was when he spread a huge canvas sheet on the floor, and then released a stream of ball bearings from a funnel in the roof of the lecture theatre.
At the level of the bench, the balls struck a metal disk on the end of a 3 metre long pointer pivoted along its length.
The imact of the ball bearings caused the pointer to lift, and the end opposite where the ball bearings struck, began to flutter.
Then he turned towards us and said "That's what Brownian motion looks like".
And not a bullet point in sight.

Max Atkinson said...

Did you ever get to hear any of Bragg's Christmas lectures, I wonder?

I was given 'Advice to Lecturers' by his daughter, who was a delegate on one of my courses at the Henley Management College.