PT Puzzle: Card Logic

Image: Puzzle cards that read, R E 7 2
Yuko Miyake
Puzzle 1: Each card has a letter (consonant or vowel) on one side, and a number (odd or even) on the other.

Rule: If there's a vowel on one side of the card, there is always an odd number on the other.

Challenge: How many of the pictured cards must you turn over to see if any break this rule?

Image: Puzzle cards with icons for soda, wine, adults and children

Yuko Miyake
Puzzle 2: Each card has two people (over or under 21) on one side, and what they're drinking (soda or wine) on the other.

Rule: If someone is drinking wine, he or she must be over 21.

Challenge: How many of the pictured cards must you turn over to see if any break this rule?

The Science: Why is Puzzle 2 easier to figure out? Our familiarity with scoping out underage drinkers makes it more tangible. "The brain deals better with things that are readily identifiable, that you have experience with," says neuroscientist Richard Restak. Familiar situations are meaningful, and meaningful information is processed between the frontal lobe and the temporal lobe, a brain pathway involved in deep understanding.

But the context-free logic of Puzzle 1 uses a pathway between the frontal and parietal lobes. We can't tie our own memories to it, says Restak, so the numbers and letters on its cards appear arbitrary. It skirts the circuitry involved in making sense of something well enough to explain it.

So how can we keep our cortices up to speed? Puzzle designer Scott Kim advocates "working abstract concepts into real-world scenarios" by drawing diagrams or making analogies. That can close the gap between meaningful and arbitrary information, "so you end up using the part of the brain that enables you to think more clearly."

Puzzle adapted from The Playful Brain by Richard Restak and Scott Kim (Riverhead Books, 2010)

Answer: In both puzzles, the smallest number of cards you need to flip is two. In Puzzle 1, you must turn over the E card to check for an odd number and the 2 card to make sure there isn't a vowel on the other side. (Turning over the R won't help, since it's not a vowel; neither will turning over the 7 card, since what's on the other side is irrelevant.) Only 25 percent of people get Puzzle 1 right, so if you stumbled, you aren't alone. In Puzzle 2, you must turn over the wine card (the rule is broken if the opposite side says under 21), and the under 21 card (seeing wine breaks the rule). Over 90 percent of people get this one right.


photo: Diego Cervo/Shutterstock

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