Here’s a holiday quiz question for you: what do puzzles, poker, and misinformation have in common? The answer is at the bottom of this column.

Let’s try an easier question first. In Santa’s workshop, if it takes five elves five minutes to wrap five presents, how long does it take 50 elves to wrap 50 presents? You probably know the answer to that one; it follows a classic formula for a trick question.

But as you groped towards the correct answer you may have had to fight off your instinct to blurt out a tempting wrong answer: 50 minutes. The arithmetic is no challenge for an astute FT reader; the difficulty with this problem is pausing for the brief moment necessary to carry that arithmetic out, while fending off the obvious but incorrect answer that pops into your mind unbidden.