There are sensible reasons for irrational behaviour

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If we are persistently irrational, perhaps the behaviour is not irrational.

Imagine you are in a helicopter above Los Angeles without a chart and want to fly to Reno, Nevada. In what direction would you fly? Of course, it is a trick question. The coast of California slopes in a north-westerly direction and although Reno is inland and Los Angeles on the sea, Reno lies slightly to the west of LA. There are many similar paradoxes: Edinburgh is located west of Liverpool, Rome east of Venice. Our mistaken answer illustrates the fallibility of human judgment.

Or does it? Get real. Anyone in a helicopter above Los Angeles without a chart and wanting to fly to Reno, Nevada, is a fool and should lose his pilot’s licence. The usual way to go from Los Angeles to Reno is to take Highway 5 north to Sacramento and then turn east, as you would expect, on Highway 80.

If you were in a helicopter above Los Angeles without a chart, you would be well advised to follow a similar route, and not just because pilots without navigational aids are often advised to use main roads for guidance. If you attempted to fly directly to Reno you would collide with Mount Whitney.

What we keep in our heads is not the real map of California, or Britain, or Italy, but a stylised, simplified map organised around a north-south, east-west grid, and the stylised map is in fact more useful to route planners than a truer representation. Juan Luis Borges told the story of the competition to produce the most perfect map: the winning entry was completely useless because the most perfect map is a full-size reproduction of the world.

The helicopter pilot is the signature example of one of the earliest of the growing stream of books about our supposed irrationality, which assert that our analytical skills are poor and our judgment faulty. But if we really are “predictably irrational”, why does this behaviour persist? Perhaps evolution is smarter than the authors of these books.

When people read quickly “a bird in the the hand”, many omit the redundant “the”. But who is making the mistake? Is it the subject, trying to make sense of a silly task, or the experimenter, who devised the silly task to elicit the mistake? The practical skill of making sense of statements that do not say exactly what the writers intend is useful even if it sometimes leads us astray.

Should we conclude from optical illusions that we should eschew our judgment of space and distance in favour of careful measurement and calculation? Perhaps, but if we did we would find it difficult to walk down the street, far less drive a car. Our judgment of speed and distance, although fallible, is also remarkable. The most sophisticated optical equipment with extensive computing capability struggles to replicate the performance of a small child, and does not stand comparison with that of a cat or a fly.

Analytic skills are neither necessary nor sufficient for good operational performance, as the many barely articulate Olympic medallists demonstrated. The Wason test is a meaningless card game used by experimental psychologists. Most participants muff it when it is simply presented as a card game. Faced with the same problem in a practical, social context, most people master it easily.

These demonstrations of our supposed irrationality mostly involve artificial situations – the helicopter pilot without a chart, the phrase deliberately framed to mislead – in which sensible, practical rules that we use to get through the complexities of everyday life give misleading answers. The skills we inherited from our ancestors and learnt as children are not always appropriate. Mistrust people from other tribes, a useful rule for most of human history, is a destructive principle in an age of cheap travel and mass migration. But that means we should understand our behaviour better, not discard the evidence of experience. There were no collateralised debt obligations on the savannahs or even when I was at school. But the old rule of “don’t eat something if you don’t know what’s in it” would have served investors well.

A cheery disposition is often objectively unjustified, but makes life better. If irrationality is predictable, it probably isn’t irrational.

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