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A PHYSICIST WRITES . . .
(October 2008)
A reader suggested that I write a column on “the fantastic capabilities of the brain, in routine driving situations.” Over the years I have looked at several of its capabilities in relation to driving (and fantastic is not too strong a word for them), but I think it would be interesting now to try to survey everything that the brain does to keep you safe — and to put you at risk! — while you’re at the wheel.
Driving is obviously a multi-task activity: many things are being done at once. Yet we are never concentrating on more than a small number of them at any time. The others are happening either semi-automatically (so we can focus attention on them if necessary), or subconsciously and out of our control. It’s extraordinary to think that our brains acquired the ability to learn such a highly complex activity long before vehicles appeared. What evolutionary step gave us this power, you wonder, ready to be applied when the time came?
The first essential when we’re driving is information. Most of it reaches us through the eyes, which send it on into the brain. Here, you might assume, the images from each retina are just put there for you to look at. Not at all: your subconscious brain deconstructs these two distorted, upside-down and mostly fuzzy images and, from the bits, builds an astonishing imaginary model of the scene in full 3D. This model is what you ‘see’ — usually with nearly all the items in it already recognized, from your vast memory of things.
And you wouldn’t believe the quantity of high-speed brainwork that has gone into assembling it: detecting lines and boundaries, sensing colours and motion, then merging the input from the two eyes to grasp the solidness of objects, and finally trying to identify everything in view. I have read that between 1/4 and 1/3 of our brain-cells are employed in processing what our eyes see.
In order to cope with this huge subconscious workload, the brain has to set priorities. Sometimes these favour what you are consciously looking at while driving, and sometimes they don’t. Either way, they can get you into trouble! For example, when concentrating hard on a vehicle just ahead (whether it’s parked or on the move) there’s quite a risk of not seeing something significant happening further on, or to the side, simply because the brain decides it’s not significant and so doesn’t bring it to your conscious attention. Good advice, therefore, is always to keep your eyes and your attention moving around.
But even this can leave us unaware of vital things. Suppose a road is joining from the left, and you are rapidly scanning it (and your mirror) for merging traffic: if another car is exactly in line with the door-pillar, with only its front and rear ends visible, there’s a real danger that the subconscious brain will not bother to connect them together and allow you to recognize them as the vehicle you are looking out for. Similarly, when only a small part of a car is visible in the side mirror, you may not see it as such. The answer, perhaps, is to remember to look consciously for the ends of vehicles, also for anything that appears not to be moving much (relative to your own car).
While all the information is coming in, different parts of the brain are interpreting traffic signs, monitoring traffic lights, coordinating your limbs to control the car, reacting to hazards, deciding if you should accelerate or slow down, planning the course ahead and then checking that you’re keeping to it — and, all the while, consulting your memory of the rules of the road to ensure you stay within them. What a tangle of conscious, semi-automatic and subconscious processes working together!
I’ve said in the past that it’s often not easy to estimate your speed (other than from the speedometer). But isn’t the brain clever at judging relative speeds, in other words how fast other vehicles are moving past you, or across your path. You know exactly where they will all be, at any point over the next few seconds ... or at least, you think you know. The problem is that the brain isn’t nearly so good at detecting acceleration or braking (unless you see brake lights, of course). So you may need to allow quite a margin, when aiming to slip past another car.
Looking further at memory: your long-term memory holds not only the rules of the road as I mentioned (plus your own ‘personal’ driving rules and habits), but also knowledge of countless routes, both on the map and along real roads. And on the road, short-term memory is needed to remind you of the speed limit, what gear you’re in, and what ‘driving situation’ you’ve just been through — in case you have to stop suddenly and be a witness!
Sometimes, though, I find myself realizing (you too?) that I have no recall at all of the last stretch of road or how I negotiated it. If my subconscious was doing the driving, was it doing it safely? And looking ahead (into the future, I mean), will I be able to detect when my driving really begins to deteriorate?
Because another thing the brain is clever at is concealing one’s ‘defects’ from oneself: blind spots in the eyes, worsening reaction time to emergency situations, the onset of poor body coordination, or perhaps deterioration of the brain itself. No wonder that some ageing motorists are unaware — or they deny, at least — that their standard of driving is starting to drop. As for me, I am not even sure I’ve remembered to say everything that I meant to about the brain, in this column!
Peter Soul
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