IMAGINE there are four cards on a table in front of you, on which are written
“A”, “D”, “4” and “7”. 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’t.
If you find it hard, don’t worry. You’re 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—but 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: “I can’t operate!
That’s my son!” What happened?
If you can’t 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: “The surgeon’s his
dzٳ.”
The stormy-night puzzle is a test of your ability to apply the 14th-century
principle of Occam’s razor, often translated as “Do not multiply entities
unnecessarily.” Or, in a 21st-century version, “Whatever happens, try all
possible ways of explaining it in terms of things we already know about, before
introducing aliens or dark matter.”
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 “a
surgeon is a man” is a case in point. Huge amounts of bad
science—especially, these days, bad evolutionary psychology and genetic
determinism—are caused by accepting such received wisdom.
Another, subtler, case is the assumption that there is—outside criminal
law—such a thing as evidence. Karl Popper’s assertion that experiments can
only falsify theories really works. And that’s 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’t 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’re doing and take up science immediately. It
needs you.
