You’re presented with the four cards above. Each has a number on one side and a color on the other. Which card(s) must be turned over to test the idea that if a card shows an even number on one face, then its opposite face is red?

In a 1966 study by Peter Wason, fewer than 10 percent of respondents correctly indicated the 8 and brown cards.

Interestingly, respondents perform significantly better when they’re presented with the same task in the context of policing a social rule (e.g., the rule is “If you are drinking alcohol then you must be over 21” and the cards are marked “27,” “16,” “drinking Coke,” “drinking beer”). About 90 percent of people perform this task correctly — supporting the idea that our facility for such tasks evolved to catch cheaters in a social environment.