Your brain is a wonderful thing. Some brains are more wonderful than others, of course (such as my wife’s) And people have been researching how they work for a long time. Even before neuro-science became popular (or even possible!), people were looking our learning capacity…
How does this research apply to presenting?
Way back in the depths of time (in terms of psychology as a science), George Miller was looking at how memory worked. In 1956 while at Princeton University’s Department of Psychology he published a paper in Psychological Review which looked at something called ‘working memory,’. It’s now one of the most cited papers of all time! There’s an online version which has Miller’s approval at: http://www.musanim.com/miller1956/ It’s largely a review of previous work and is written quite nicely, even if it’s a bit old now.
You can think of working memory as the amount of information you can cope with at any one time. When it gets overloaded you start to be unable to process things – a bit like a juggler taking more and more balls until it all gets a bit much and balls end up on the floor. An alternative analogy might be a we browser that has so many tabs open that it can’t really load any of them properly. (My worst case was 19 tabs.)
Just like a juggler, different people are different: some can juggle different numbers of balls while some can process different numbers of facts at once.
Miller’s paper is big and complicated (and often mis-presented to say that people can only remember seven things) but it started off looking at binary comparisons and gave rise to the idea of ‘bits’ of information. He uses height, but gender is an easier idea to work with, I think. People are either male or female (let’s assume that’s true for simplicity) and we need just one ‘bit’ of information to know which they are. What that means is that with two bits of information we can handle four possible outcomes; with three bits, eight and with four bits of information, 16 outcomes.
The simple idea shows how that might work. Using just two ‘bits’ of information…
- Bit of information one (male vs female)
- Bit of information two (with glasses vs. without glasses)
Which gives us
- Outcome 1 – man without glasses
- Outcome 2 – woman without glasses
- Outcome 3 – man with glasses
- Outcome 4- woman with glasses
You can see how quickly even binary options multiply to give us a lot of options for us to keep straight during presentations. Miller was interested in what he called ‘absolute judgement’ – which means he ignored things such as how fast someone can process bits of information – and concentrated simply on how many bits they could handle at one time. For example, this can be done by asking people to identify different musical notes in a sequence/set, and counting how many times they get it right.
So how limited are presentation audience’s memories?
He comes to a rather depressing conclusion about how smart we are, as a species.
For just one, two or three notes, people rarely get confused. Increasing to four different notes means mistakes are still pretty unusual. That makes sense. Then, rather suddenly, if five or more notes involved, mistakes become pretty commonplace. What this seems to mean is that presentation audiences (well, anyone really!) can only handle a limited number of bits of information at a time before things start to get out of hand and our juggler starts to be glad he’s using juggling balls and not raw eggs.
Depressing, eh? It means you’ve to to keep your presentations more simple than you thought.
What’s more, it’s important to remember that all of this is based upon looking at only one dimension at a time. In our example musical notes range in only one dimension, from ‘low’ to ‘high’. When you start to look at things which vary with multiple dimensions things get messier quickly.
All in all, Miller suggests that we can only cope with around seven bits of information. I’d like to think I can remember more than that, of course, because I’ve got more than seven friends and they’ve got different names, but that’s not what Miller was talking about. He was looking at how much information we can handle at a time… and for the presenter that is critical!
The final result is the so-called Miller’s Law: people can handle seven pieces of information at a time, plus or minus two.
Don’t panic: stay with me, because I’ll look at the bigger picture in a bit. But for now, how you apply Miller’s Law to your presentations should be pretty obvious and can be summed up like this: don’t overload your audience with too many facts and figures at once. They can’t cope and they’ll start to make mistakes, getting confused between them. It’s a bit like trying to watch a TV programme with so many characters that you lose track of who’s who, particularly if they’re similar to each other. If one twin is good and the other is evil, but there are too many people all together and one of the characters is wearing another one’s clothing… well I just get confused.
I need tags or subtitles as characters come on the screen to remind me who they are. “James – John’s brother. He’s the one who was by the river with his friend’s wife two scenes ago but with her sister in the same place two episodes ago. He’s also had plastic surgery, so you need to remember he was also the person who started the fire in the chip shop.”
Is it just me, or does that sound like an episode of Hollyoaks?!
As it turns out, therefore, your presentation’s audience needs these tags as well. They can’t keep too much information in their heads at once. Maybe it’s just coincidence but ask yourself how many central characters their are in successful, long running sit-coms or adventure series. There were six Friends; the Starship Enterprise had a crew of over a thousand but we were only ever interested in seven or so; Big Bang Theory has about the same number of key characters. Don’t get too hung up on that – there’s no evidence behind this paragraph other than my tendency to watch too much TV.
Let me try to recover my credibility.
I once read Steven Hawking’s “A Brief History of Time”. It’s a great, great book but it contains so much information it’s impossible to read and absorb at one go, especially as much of the information is challenging. I found myself understanding each and every page I read at the time I read it, but unable to remember what I’d read more than three pages ago. I had to keep going back over material to remind myself what X meant, so that I could understand how it fitted with Y to give Z. The only reason I got through it was because I was stubborn (and on a bet).
What are the presentation take-aways here?
- Don’t give your audience long lists of things – or at least don’t do so if you expect them to be able to remember or compare them. Don’t ask them to rank more than seven or so things. Stick to the limit of what people can process in the moment. Don’t give example after example after example to prove your point – there’s no point!
- When you’ve got lots of information, there’s no advantage in bombarding your audience with it. You’ve got to drip-feed it. And then you’ve got to wait. You’ve got to wait until they’re ready to move on. (See this guest-blog on the half-life of ideas in your presentations.)
- Keep it simple. Are you sure you need every single fact, figure or item of information you’ve included? Would a summary do? An average? A lot of presenters include stuff that’s not necessary out of fear of missing something out and end up drowning their audience. When you’ve written your presentation, go back over it again, looking at your facts and see if you can cut them.
- Be brutal – don’t ask if you can cut it. Let your default be to ‘cut’ and see if you can justify it, remember that you’ve only got 7±2 to play with!