In a totally sweet New York Times article of this title, John Tierney discusses a probability experiment conducted by professors Craig Fox and Jonathan Levav.
Here’s how it works.
One of the profs shuffles five cards, one of which is an ace, and then deals two cards to a participant and keeps three for himself. All cards are facedown. No peeking. If the participant’s hand happens to have the ace, he earns $1.
Easy, right?
Here’s the first twist: The prof peeks at his own cards and then offers the participant the chance to switch hands. Duh. Most of the participants see that the odds of getting an ace are 3 to 5 for switching and 2 to 5 for keeping their own hand, and so most of them choose to switch.
Now, what do you think happened when the good professor told a second group of participants that he would look at his cards, turn up two cards that are not the ace, and then offer them a chance to switch hands?
Check the answer. It’s as good as the puzzle.
Psy-Op: Pick a Number, Any Number
For this trick to work, you gotta do it like you mean it. Do the math in your head as quickly as you can. Then flip to the back for the answer. Ready? Go!!
What is:
6–2?
8–4?
12–8?
16–12?
Now quickly pick a number between 12 and 5!