The three of spades

There is a fascinating sub-culture in the circles of magicians and illusionists called magic for magicians. It relies on the fact that a professional magician knows how most tricks are done and can work out how others are performed based on this knowledge and understanding. To fool these people requires something very special, or in fact, perhaps something very simple:

Present a deck of 52 cards, ask you magically minded friend to select one at random, look at it, and put it back in the deck. You the peel off his three of spades as the top card on the pile.

The expert has the eye to know that you didn’t force the card on him, he saw no slight of hand when you revealed his card, no distraction at the key moment, no, well, anything. How was this done? As a non-magician, you might have guessed already. Every card was the three of spades.

This works because the magician is looking for the complex and is fooled by the simple. He wouldn’t dream of trying to trick someone with so crass a trick and so would never think that it might be tried on him. It’s an obvious ‘wood for the trees’ issue.

This could, (and will in some quarters I suspect) be used as an example for certain overly enthusiastic and overconfident people to show how researchers have made mistakes because of their expertise. But I don’t think this is right, the magician might be fooled in the short term, but only because he started too high up the ladder of possible solutions. He certainly has the knowledge and experience to work back down the chain of complexity and work out the problem. However, it does provide a salient lesson in checking your assumptions (here that the deck was normal) and making sure things you think you know, or expect to be the case (card trick generally start with you showing the deck to be normal) really are.

Though even if you don’t check it, someone else will sooner or later. And again, that breadth and depth of knowledge that works across the branches of science and the individual researchers will soon spot a miss-step in assumptions or reasoning. But still, no reason not to have another look yourself when confronted with a surprise.

1 Response to “The three of spades”



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