There is actually a "mind trick" where you make someone choose a number between 1 and 4, guess it is 3, then make them choose a number between 1 and 10, and guess it is 7. It works, because there is a statistical bias toward these numbers, but the way you do the trick is also important (the way you gesture with your hands primes the person to answer with these numbers).

I've always loved such mind tricks, and I have done this one quite a few times. Before discovering HN, I used to go out a lot, and, when talking to cute girls, I've done this "trick" many times for giggles. Some girls really believed I was a psychic when I got it right :)

Funnily enough, knowing about this trick and the "statistical preference" for the number 7 made me choose 7 in this experiment, without thinking twice about it. I realized this afterward...