The question is, which cards do you turn over to test the truth of the statement? Try to select the fewest cards that will do it. The Wason Selection Task was developed by English psychologist Peter Wason to study how people think. They often don’t think rationally.
I found the most difficult part was finding my answer among the multiple choices, because there are a lot of them. More than 90% of Wason’s original subjects selected the wrong answer. Maybe we are doing better in the 21st century, because when I snagged this video, 20,626 people had viewed the puzzle video, and 5393 had viewed the correct answer. However, that number may have been skewed by people checking out all the answer videos. I didn’t bother checking the incorrect answers. You can read about Wason’s research into the human tendency to select irrational paths at Nautilus. -via Digg
Update: Oh, okay, I clicked a wrong answer, and the video it went to gives you the option of seeing the correct answer video. That explains why the correct answer had much more than 10% of the views of the original.