This column originally appeared in The Observer magazine/Guardian online

Are you an optimist or a pessimist? Is the glass shown below half full or half empty?


Just kidding. These days, psychologists have much more sophisticated ways of probing your optimism.

So, in percentage terms, how likely do you think you are to be diagnosed with cancer at some point in the future?

The average rate (according to Cancer Research UK) is 50%. Would you like to move your guess up or down?

Now, in percentage terms, how likely do you think you are to suffer a domestic burglary over the next 12 months?

The average rate (according to the Crime Survey for England and Wales) is 3%

The extent to which you changed (or didn’t change) your answers in response to the facts is a measure of your optimism. On the whole, most people are optimistic, and change their answers more when doing so gives a favourable than unfavourable outcome. For example, suppose that you estimated your risk of cancer at just 20%. On hearing that the population risk is 50%, most people up their guess a bit, but not by much (and rarely as high as 50%).  On the other hand, suppose you estimated your risk of burglary at 10%. On hearing that the population risk is just 3%, most people lower their guess quite a bit, often to 3% or even lower. If you changed your answers unfavourably (or not at all) then you’re either a pessimist or a realist.

In fact, the two are probably one and the same. Since most people go around with a rose-tinted view of the word, anyone who doesn’t seems unusually pessimistic by comparison. Many psychologists argue that the reason behind this optimism bias is that, in many cases, dwelling on the true odds of life’s various misfortunes would be just too awful to enable us to go about our business.

NB: Although the Independent reported that this claim was debunked in a recent study, another study debunked this debunking. It will be interesting to see whether the authors of the former study issue a re-debunking that debunks the debunking of their own debunking.

A fully referenced version of this article is available at Order Psy-Q by Ben Ambridge (Profile Books, £8.99) for £6.99 at

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