continuity bugs in linear slide presentations

Whenever you take a non linear media and flatten it (make it linear), you introduce problems of two kinds:

1) Discontinuities in logic. The audience needs to remember what was connected to what, earlier in your presentation, to see the connection logic.

2) Discontinuity in time. As time passes, the audience remembers less and less of what they heard and saw. As a result, the memory fails to reconnect the time-broken strands of a disrupted argument.

Here is an illustration. Each square represents a slide. The slides are numbered from 1 to 5. The eroding effect of time on memory is here symbolized by the greying of colours, from dark (last slide best remembered) to grey (started to fade in memory) to dotted line (first slide, may have been presented 8 to 10 minutes before slide 5, vague or no longer remembered).

flattening problems

I assume here that all slides are equal in duration. Things worsen when slides are text heavy. We have all encountered slides that are so dense in information and take so long to explain that the audience has forgotten what was said at the beginning of the slide by the time the end of the slide is reached!

So here is my tip:

Visualize the logical connections between your slides, either as a domino or a graph. This will help you identify the potential memory-related problems your audience may face. And apply one of the following solutions to remove these problems.


The Announce technique consists in telling the audience what will be covered in the next (two) slides. The audience, once alerted, finds it much easier to keep the information of slide 1 in memory and relate it to slide 2 and 3.

The Repeat technique simply re-presents past information so as to be able to refresh fading memory (like the refresh cycle that keeps RAM memory alive!)

The Merge technique consists in keeping on the same slide all related elements, presenting them one by one (one at a time) to avoid overwhelming the audience with too much information at once, but allowing people to see past information on the same slide. Naturally, this is only possible if the slide can contain these related elements without losing readability.

The Restructure technique, as its name indicates, looks at alternative structures that would enable the contents to be presented without discontinuities.


By Jean-luc Lebrun