Here's a really simple parlor trick that my young daughter (who is now grown up) and I used to pull on guests:
I would tell the guests to pick a number from one to five. I would have them whisper it in my ear. I told them that I would send the number across the room via telepathy. My daughter invariably "guessed" the number.
How did she "guess" the number? After I got the number from the subject, I would use that number of words to address my daughter.
Examples:
If the subject guessed one, I'd look at my daughter and say "Well?"
If the subject guessed two, I'd look at my daughter and say something like "Got it?"
If the subject guessed three, I'd look at my daughter and say something like "The number is...?"
If the subject guessed four, I'd look at her and say something like "What is the number?"
If the subject guessed five, I'd look at my daughter and say something like "What number are you getting?"
It works like a charm and people almost never guess how it works.
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