IMAGINE there are four cards on a table in front of you, on which are written
鈥淎鈥�, 鈥淒鈥�, 鈥�4鈥� and 鈥�7鈥�. You are told that each card has a number on one face and
a letter on the other. You are also told that the rule is that a card with a
vowel on one side has an even number on the other. Which card/cards do you have
to turn over to find out whether the rule holds true? This is a version of the
Wason test beloved of experimental psychologists. It would be a disservice to
the discipline to reveal the answer while there may still be papers to publish
about it. So we won鈥檛.
If you find it hard, don鈥檛 worry. You鈥檙e in good company. Over many
repetitions of the test, designed to include a wide variety of subjects (though
doubtless with a real-world skew towards readily available undergraduates),
fewer than 10 per cent get the right answer. You may still be a gifted human
being, and you might even make a good lawyer or musician. There is, however,
strong reason to doubt whether you should be a scientist.
Before dealing with that arrogant assertion, try another puzzle.
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It was a dark and stormy night. A man was driving his son home. The car
skidded off the road and hit a tree, killing the father instantly. The son was
seriously injured鈥攂ut with the kind of luck necessary to make stories
work, an ambulance was passing and took him to hospital. There, he was wheeled
into the operating theatre, where the surgeon exclaimed: 鈥淚 can鈥檛 operate!
That鈥檚 my son!鈥� What happened?
If you can鈥檛 work this out, you should definitely never design an experiment.
You are also disqualified from being a feminist. This is embarrassing to the
majority of self-defined feminists, many of whom propose ever more bizarre
explanations heading resolutely away from the answer: 鈥淭he surgeon鈥檚 his
尘辞迟丑别谤.鈥�
The stormy-night puzzle is a test of your ability to apply the 14th-century
principle of Occam鈥檚 razor, often translated as 鈥淒o not multiply entities
unnecessarily.鈥� Or, in a 21st-century version, 鈥淲hatever happens, try all
possible ways of explaining it in terms of things we already know about, before
introducing aliens or dark matter.鈥�
The key to doing this well, or at all, is to throw off the shackles of
established ways of thinking about known entities. The unstated assumption 鈥渁
surgeon is a man鈥� is a case in point. Huge amounts of bad
science鈥攅specially, these days, bad evolutionary psychology and genetic
determinism鈥攁re caused by accepting such received wisdom.
Another, subtler, case is the assumption that there is鈥攐utside criminal
law鈥攕uch a thing as evidence. Karl Popper鈥檚 assertion that experiments can
only falsify theories really works. And that鈥檚 a hint about how to approach the
Wason test and identify bad science.
A final puzzle. After your first day in a new job, you arrive late at an
office party. You see one couple kissing. And a second couple not kissing, whose
hands you can鈥檛 see. And a third couple wearing matching wedding rings. And a
fourth couple not wearing wedding rings. What further observations of these
couples do you have to make to establish which of them are having extramarital
affairs?
This is, of course, another trick. If you find the connection with the first
puzzle obvious, drop whatever you鈥檙e doing and take up science immediately. It
needs you.