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A PHYSICIST WRITES . . .

(October 2013)

If I say that I weigh my words, you will know what I mean. But if I say I also weigh other peopleís words, I shall need to explain! Firstly, my collection of books (not to mention Mrs Sís own collection) fills 19 metres of shelf length, and I know Iíll never live long enough to read or reread everything I want to. So I aim to avoid bookshops Ė and when that fails, I try hard to resist buying yet another book, succumbing only if the number of words in a tempting one is out of proportion to the price. This adds one more tome to my reading-list, but I canít help it.

And then when packing for a holiday, I find Iím weighing words again: did you realize that even just among paperbacks, the words-per-kilo rate varies by more than a factor of two?  Hence I tend to pick out books from the shelves that will give me more words for less load...

Which is how, last summer, I got to know a most readable book called simply Risk, by Dan Gardner. I can recommend it to anyone who may be interested in understanding why individually we find it hard to assess the dangers we and the world might be facing Ė and how this inability of ours is exploited by the media, by politicians and by every type of organization.

Hereís an example: when people are asked in surveys, it turns out that they believe they are much more at risk from terrorism and violent crime than they really are (from analysis of the statistics). This is of course because of all the media stories, both reported and fictional, that they see about such activities. And the result is that politicians and others get public support for taking costly and unreasonable preventative measures, including imposing restrictions on us all.

The book kicks off with the astonishing fact that road deaths in the US rose by 1600 in the twelve months following 9/11 (they then returned to Ďnormalí). Fear made travellers turn from planes to cars, misjudging the risks involved. In fact they would have been far safer in the air than in vehicles even if terrorist attacks were a regular occurrence.

Mr Gardner doesnít have much else to say about danger on the road, however, so I thought I would outline some of his psychological basics and see what emerges when I try to apply each of them to driving...

Head versus Gut: we think in two quite different ways. It was Ďgut instinctí that saw the human race safely into and through the Stone Age. Then later we developed Ďhead reasoningí, in order to cope with the modern world. But Head is slow, and unable to control or understand Gut, while Gut only learns gradually from Head. When a quick decision is needed, Gut takes charge, for better or worse. (You could say that Head and Gut are conscious and subconscious thought, respectively.)

I might start by mentioning that riding (ie, staying balanced on) a bicycle is entirely a matter of quick decisions by Gut, with Head having practically no idea how itís done! By contrast, learning to drive requires a great amount of thinking, during which Head grapples with all the automatic skills needed, until finally Gut absorbs them. Worryingly, among the most important skills is reacting correctly in an emergency: this is almost entirely Gutís responsibility Ė but where is there an opportunity to practise it? Only on a skid pan or on an empty road...

The Anchoring Rule: Gut pulls Head this way and that. Suppose you need to guess or come up with a quick numerical value for something, but you donít have much to go on: if you happen to see or hear a possible number mentioned, then without your realizing it at all, your response will be shifted towards that value (even if itís an unlikely one). As an example, if you are being tempted by a special-offer display in a shop, and you then notice a sign, Limit of 12 per customer, you will very probably take more items than otherwise.

I donít need to explain how this rule applies to buying/selling a car with a carefully chosen asking-price attached! Iím more interested in what it suggests about speed-limits, namely that seeing a 40 or 50 sign at the end of a 30 mph stretch will induce drivers to accelerate straight up to the new limit. And then, presumably, each repeater beyond will encourage them to stay there (also reminding them not to exceed the limit, of course).

As an advanced driver, I always thought that the reason I drive near to the limit, when itís not silly to do so, was the instruction given to me long ago to make good progress. Now I suspect that my subconscious is simply reacting to the number on the sign as a target, as if an internal cruise control is being readjusted!

But hereís the crunch question: what is the effect on the average driver of seeing an NSL or national speed-limit sign (plus any NSL repeaters)? Bear in mind (a) that this sign was perfectly designed, originally, to say No Speed Limit At All, and (b) that a significant fraction of motorists are unaware that it really means a 60 mph limit (or 70 on dual carriageways and motorways). Anyway, I know what I believe: NSL signs are a danger to us all...

Confirmation Bias: once you hold a particular belief, you pay more attention to further evidence that supports it than you do to anything contradicting it.

Therefore no, please donít bother me with survey results indicating that NSL signs are in fact fully understood by everyone! Instead, what Iím thinking here is that having recently upgraded from an old Corolla to a newish Golf, I am enjoying driving a (relatively) luxurious car: comfortable seat, inaudible engine, good acceleration and brakes, and plenty of safety technology. Hence each time I find myself on a motorway in fast heavy traffic, I relax in an increasingly strong belief that Iím in firm control, well protected, and indeed hardly moving at all (relative to the surrounding vehicles, at least).

But hang on: in reality Iím travelling at a fearsome speed, I am no better a driver than I was before, and nor is everyone else around me! I must remember the danger Iím in. Thank goodness, then, for...

The Example Rule: letís say youíre wondering how much at risk you are from something, such as a particular disease. Almost certainly, your Gut conclusion will be influenced a lot more by how easily you can recall facts about it or examples of it, than by what these may actually be telling your Head about the threat.

This effect constantly generates misguided levels of concern: if a human case of bird flu in the Far East hits the headlines, people everywhere reach for face-protectors. Conversely, popular opinion says that diabetes (an example of an unnewsworthy disease) causes far fewer deaths than road accidents Ė whereas in fact itís the much bigger danger. However, the point I want to make here is that stories of events like Septemberís multiple crash in foggy Kent, splashed on front pages of newspapers, are a good thing in one way: they ought to have the effect of reminding all drivers to weigh up what theyíre doing.

Peter Soul

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