Here is a well-traveled card trick/mindreading illusion that has popped up again and again on the Internet, even circulating in the form of a PowerPoint presentation purporting to be (though it almost certainly is not) the work of master stage magician David Copperfield.
The illusion can be startling, until you figure out how it works -- at which point you may find yourself wondering how anyone could possibly fall for such a simple, obvious deception.
It goes something like this:
I can read your mind!
Don't believe me? Here, I'll prove it.
Take a look at these 6 cards:
Now pick one, just one, and hold the image in your mind. Concentrate!
Are you thinking of the card?
Excellent.
I will now, through the magic of the Internet -- even though we're not in the same room and possibly not even on the same continent -- read your mind...
Got it! I know which card you chose. I will now make it disappear...
Voila! It's gone!
Amazed? Don't be.
This is truly one of the simplest yet most effective mindreading illusions ever devised. How does it work?
Take another look at the "before" and "after" card layouts and all should become clear:
Fig. 1
Fig. 2
See it? The obvious difference, besides the fact that there is one less card in Figure 2, is that none of the cards in the second layout are the same as in the first. I didn't just make your chosen card disappear - in effect, I made all of them disappear, replacing them with different ones.
Like most magic tricks, this one depends on misdirection: since our attention and memory are focused on just one card out of the six, most of us fail to absorb any details about the other five cards. Hence, when they're subsequently replaced by a set that looks approximately the same, we accept it as exactly the same. Voila!
From the Guide to Urban Legends on About.com
