Brain bandwidth – the explanation for everything

Actually, of course it’s not. It doesn’t explain why I like the colour pink. That headline was just to trap you. To occupy enough of your brain bandwidth that you were distracted from whatever else you were doing and focused on my words. And you need a lot of brain bandwidth for that. In fact, it’s estimated that listening to the human voice (which I know is not exactly what you’re doing) occupies about half a human’s brain bandwidth. What are you doing with the other half? Could you listen to another human voice, in that case? No, because you also need some bandwidth to remain sitting on your chair, to refrain from fidgeting, to think about the thing I said a few seconds ago, to wonder what I’m going to say next, to process the irritating sound of someone sniffing and to stop your tongue lolling out of your mouth, which it would otherwise actually be doing if you didn’t occupy a very tiny amount of bandwidth holding your jaw and facial muscles in check.

Brain bandwidth theory does explain a lot, though. And it is endlessly fascinating.

I first came across the concept in Scarcity: The True Cost of Not Having Enough by Sendhil Mullainathan and Eldar Shafir and then again in The Organized Mind: Thinking Straight in the Age of Information Overload by Daniel Levitin, two books which have been most influential on me and which I quote from regularly in my talks. I’ve applied it to my experience of the world around us and here is how I explain it.

Think of broadband bandwidth. For any broadband-connected device there is a finite amount of bandwidth. If someone is using a significant amount of it – streaming, for example – there is less left for everyone else and other things will happen more slowly or not at all. You’ll notice this especially when using wifi on a train. Grrr.

The brain works in just the same way. Our bandwidth for conscious activity (mental or physical) is finite. (Cognitive scientists have measurements for it but these measurements depend on exactly what is being measured, and that varies. Levitin quotes one measurement – 120bps and the 60bps human voice rate I mentioned above – from Csikszentmihalyi, the founder of the concept of “flow” and Robert Lucky from Bell Labs.) Everything we do (thinking and doing) occupies some bandwidth. Some things occupy a little and others a lot. Examples of things that occupy a little, for most people, are: walking, drumming your fingers or tapping your foot, and things that we are very very expert at because we’ve done them often. Examples of things that occupy a lot are talking, listening to information, doing anything we have to concentrate hard on, doing things that we are not expert in because we haven’t done them before.

As with broadband, when something is occupying a lot of bandwidth, other tasks happen more slowly and less well. (Though we can learn to do two particular tasks together if we practise. See below.)

Driving a car is a good way to envisage this. When you were learning to drive, you had to concentrate extremely hard. You would not have been able to hold a conversation while driving. Almost all your attention (which is another word that fits with the brain bandwidth concept) was involved in trying to drive. Now that you are an expert, because you’ve done these actions so many times that they have become somewhat automatic, you don’t usually have to use so much of your attention. Of course, you still have to use a fair amount, but you could also have a conversation while driving. But then, every now and then while you’re driving along, something happens that means you have to focus more: the traffic increases, you come to a part of the journey where you have to look out for a turning, roadworks happen, the weather becomes difficult. Then you will find that you tend to stop conversation; you might turn the radio off; you have instinctively realised that you need more brain bandwidth for the driving.

A few more interesting examples:

  • If someone is walking at their own pace while being asked simple but increasingly difficult mental arithmetic questions, they will begin to walk more slowly as the sums become harder. Eventually, they usually stop. I’ve tried this with audiences – it’s hilarious!
  • When I do public speaking, I don’t walk about. At all. When I explain to the audience that the reason I don’t is because I can’t, because too much of my bandwidth is taken up by talking and there’s not enough for walking, they laugh. But then I go on to point out that if you’re walking along chatting to someone you will slow down or stop when you come to something important or shocking or difficult, and they all start nodding. It’s common experience.
  • Teenagers who drive are 5 times more likely to have an accident if there’s someone else in the car with them. The explanation is usually offered that they are more likely to take risks when someone is with them. This may be true (and some fMRI evidence supports that) but I think it’s equally likely that their driving skills are less expert and therefore they are using more brain bandwidth, and the act of talking to someone distracts them too much.
  • When someone is working while listening to music, they will almost always voluntarily turn it down or off when they come to something they need lots of concentration for. Even my husband, who is definitely the world’s most obsessive music-listener.
  • I gather that when a music pupil is preparing for a performance and has got to a state of being really fluent at the piece, some music teachers will test this by asking them questions while they’re playing. What the teacher is doing is testing that the piece has become automatic and using less bandwidth.
  • Air force pilots (and I assume the same applies in other areas of the military) have to practise managing disasters over and over again because the least amount of bandwidth should be used, freeing the rest for reacting to the unexpected. the unexpected takes a lot of bandwidth so as many as possible scenarios must become “expected” or at least practise and automatic.
  • Next time you’re in a situation where two people ask you things at once, notice what that feels like in your head. And how stressful it feels!

Why is this brain bandwidth theory so relevant to wellbeing, stress, performance and all these things I’m so interested in? Here are some ways in which it really matters and in which it answers some questions or offers some context and understanding:

Stress and preoccupation

When I talk about stress I explain the benefits of it and then mention three downsides: first, that you can have too much adrenalin and have a sense of panic instead of simple alertness. Second, cortisol has a habit of building up and over time causing problems with sleep, mental health, focus, mood, performance and physical illnesses. And third, “preoccupation”.

Preoccupation describes the fact that if our brain bandwidth is occupied by “stuff” (I’ll come to what that stuff might be in a moment!) then we have less available to focus on the task in hand. If the task in hand is simple or trivial or familiar, it won’t be such a problem, but if it’s something that we really need to focus on, it could be. And it will lower our performance on that task.

Things that “occupy” our minds – the “stuff” – in other words, things that occupy a lot of bandwidth – and note that these are not necessarily bad things, not necessarily “stressful” either, just things that take up bandwidth:

  • Worries, anxieties, intrusive negative thoughts – if we’re worried about something or someone, it’s hard to focus on our work; we’ll make more mistakes; and we’ll be more snappy
  • Processing information or tasks – such as things we’re trying to learn, understand or remember
  • Anything new and unfamiliar
  • Other people being around us – they could be distracting us or making us feel unrelaxed; other people are hard to ignore
  • Working on screens – because when we are using a screen there is almost always competing information on the screen, adverts and icons and notifications designed to attract our attention away from what we are doing (I have some fascinating things to say about this in my talks for adults and older students!)

There are others but there’s a particular reason I’ve picked those ones: many (most? almost all?) young people in school are dealing with all or most of those things almost all the time.

This means that their bandwidth is being severely challenged and it’s likely often to be extremely difficult for them to keep enough focus on the task in hand.

The consequences of that

  • Exhaustion – that situation is occupying a great deal of energy – the brain is a very energy-hungry organ, as you’ll have heard
  • Mistakes and forgetfulness – you know that the times when you have “a lot on your mind” are the times when you make mistakes
  • Loss of executive control – you know that the times when you have “a lot on your mind” are the times when you snap, say and do things you don’t mean
  • Loss of cognitive ability – it’s harder to learn new things if we can’t devote our full attention

Something that adds to the problem

Too many of us – myself included – allow ourselves to occupy some of our brain bandwidth by having our phone nearby or our email window open, allowing notifications or even the thought of notifications to distract us slightly. You’ll find references to much of the science on this here. Scroll towards the end of the document.

Questions you might be asking:

  • Can we increase our brain bandwidth by practising? Probably not (except perhaps by the use of drugs but I’m not going to talk about that because a) I don’t know enough and b) I can’t believe it would be a good idea.) Those of us who try to multi-task a lot (which would presumably be how you’d try to increase bandwidth) actually get worse at doing the thing we presumably want, which is surely to perform better on the task or tasks that are important to us. As for learning to do two things at once, it seems that we can do this when it’s two specific things – for example, patting our head while making our other hand go round and round on our stomach, or using our left and right hands for different tasks, as we do in music – but this doesn’t seem to make us have bigger bandwidth, just use less of it for those two tasks. I’m not going to be categorical about this but I feel it’s unlikely that we can build our bandwidth in any useful way.
  • So, does this mean that we shouldn’t listen to music if we want to focus on our work well? I’ve talked about this here.

I think you’ll now find lots of examples in your own life of times when you notice your bandwidth being challenged. It’s also useful to notice and appreciate those times when we really do manage to devote enough bandwidth to the task in hand. For example, I really enjoyed writing this piece. I wrote it all in one go, without noticing the time, and found myself mostly in Csikszentmihalyi’s state of “Flow” – a very good place to be, satisfying and engaging without being stressful.

And now I’m going to make a cup of coffee. Fortunately, on my own because something I forgot to tell you is that I cannot talk while doing anything with my hands. If I have someone round for coffee, I have to prepare everything first, otherwise I won’t be able to talk to them. I’m not exaggerating – my hands either freeze while I’m talking or else are quite likely to be doing entirely the wrong thing, such as pouring the water onto the biscuits. Talking takes up a  lot of my brain bandwidth, much as I love doing it. I put it down to my strongly introverted personality.

But that’s a story for another day.

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