Like all good logic puzzles, the concept of Wason's Selection Task is easy to understand and its solution is kick-yourself easy once explained. But working it out isn't so straightforward.
When creating this puzzle in 1968, British psychologist Peter Wason described it as "deceptively easy".
The subject is confronted with four cards - each with a number on one face and one of two colours on the other. One shows 5, one 8, another blank with a blue face and another blank with a green face. A statement above the card reads: "If a card shows an even number on one face, then its opposite face is blue."
Which cards do you need to turn over to find out if the statement is correct?
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Answer: 8 and green
It turns out that more than 90 per cent of people get this one wrong, which, as Nautilus point out, is because the wording tricks the brain. Most people choose the eight (the even number) and the blue card because those are the ones mentioned in the statement.
Watch and listen to the answer being explained by Spiked Math below: