Read the following quickly A BIRD IN THE THE HAND. Many people who are asked to do this say “a bird in the hand”. Experimental psychologists use such exercises to demonstrate cognitive illusions. The mistakes that are identified are not random, but systematic. Very few people read “a bird in the the hand” when you have written “a bird in the hand”, but the converse misreading is very common.

But who is actually making the mistake? Doesn’t the fault lie with the experimenter who asks his subjects to parrot a meaningless phrase, rather than the subject who valiantly finds sense in nonsense? Many London taxi drivers display signs that suggest they believe London’s third airport is called Stanstead. Even Transport for London, which ought to know better, displays a sign to this effect at Baker Street Underground station – but no one has the slightest difficulty understanding what is meant. If you approached the staff and said: “I see the sign for buses to Stanstead Airport, but where do I find the buses to Stansted Airport?” you would rightly be regarded as a pedantic fool rather than a careful observer. The skill of piecing together sense from fragmented and inaccurate information is a central attribute of human intelligence. Literal interpretation, and insensitivity to context, are not marks of rationality but mental disorders.

If you ask people whether they would rather have $100 now or $110 a week from now, many people will plump for the $100. But if you ask if they would rather have $100 in 52 weeks’ time or $110 in 53 weeks, almost everyone prefers the larger sum. Yet 52 weeks from now, all those who postpone gratification could have had $100 in cash rather than $110 in a week’s time. Faced with just this situation a year ago, many chose the immediate $100.