ABSTRACT
The duration of a lecture is frequently determined by the one-hour slot allocated to it rather than by educational principles. Levels of attention and rates of learning fall off fairly rapidly during lectures. Passive attention, in particular, is prone to a sharp decline over even quite a short period. Documentary makers assume that about four minutes is the limit one can expect an audience to pay attention to the same image or ‘talking head’, and usually change the image at very much shorter intervals than this. During prolonged sessions (such as in symposia where one 20-minute presentation is immediately followed by another, without pause for breath) this use of breaks is absolutely vital. Breaks which allow uninhibited physical movement, social chat, noise, a change of seat or a breath of fresh air work better than quiet restrained breaks.
