Remember the old television show Let’s Make a Deal? Monty Hall would given contestants, typically dressed in outrageous costumes, a choice of three doors. The contestant would receive whatever was behind the door they selected. One of the doors had a great prize behind it. Pick that door and you get a valuable gift like a car or a vacation. But behind the other two doors were gag gifts. It might be a rooster or a lifetime supply of paper clips.
There was always one extra twist to the show: Once you pick a door, before revealing what was behind it, Monty would do you the favor of opening one of the remaining two doors and show one of the gag gifts. At that point, he'd let you switch doors if you wanted to do so. You could stick with your original choice as well.
What's the right move? Our instinct tells us to to stick to our guns. But you should go against that instinct and switch. Why? The chances you’ve picked the wrong door is two-out-of-three. But with only two doors left, your odds of getting the great prize goes up to 50-50.
But there’s more afoot here than just winning a prize on a TV game show.
Economist M. Keith Chen says this phenomenon has been overlooked in some of the most famous psychology experiments. He claims The Monty Hall Problem shows there's a logical flaw in the idea of choice rationalization. Choice rationalization is the idea that once we reject something, we tell ourselves we never liked the one we rejected anyway. Psychologists say we do this because it spares us the pain of thinking we made the wrong choice. Chen believes it’s not the act of picking that makes people suddenly prefer one over the other. He claims the preference was there all along. It's just that the preference was so slight it was not initially obvious until other possibilities are cleared out. You can read his own explanation here.