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Sleight-of-hand a trick of the eye

Magicians rely on illusions that have a basis in understanding how our brains work. Dr Karl steps out of the lab and on to the stage to pull more than a rabbit out of his hat.

Wide-eyed magician

(Source: iStockphoto)

Last time, after I started off talking about how to bend a spoon for fun and profit, I moved into how we can use the marvellous art of magic to uncover some of the secrets of the human brain.

I mentioned that magicians use a whole bunch of devices to entertain the audience, starting with visual illusions and optical illusions.

The third device they use is the cognitive illusion.

The magician aims to misdirect the attention of the audience. As a result, they won't notice that something has changed. This is called inattention blindness.

For example, a magician might move his hands slowly in a curve, or quickly in a straight line.

Your eyes will accurately follow the slow-moving hand, in a smooth pursuit. But when your eyes follow a fast-moving object, they don't move smoothly.

Instead, they jump from one location to the next. These sudden eye movements are called 'saccades'. During a saccade, you are effectively blind.

You actually see reality only at the beginning and end of a saccade. The stuff in between you make up and insert into reality.

Another neuro-scientific fact to add to the mix is that our brains treat curves differently from straight lines.

Straight lines are fairly predictable — they'll just go straight. But curved lines (and corners as well) are less predictable. So our brains are wired to pay more attention to curved lines. And this is something a magician can do to get you to not notice something, or to misdirect your attention.

The fourth device used by magicians is the field of special effects. These include false gunshots, impressive explosions, and so on.

The fifth device is the gimmick: mechanical devices, secret devices and so on. This might include a spoon made of a special metal alloy (such as nitinol) that might change shape at a certain temperature.

Now the right person to catch out a magician is another magician, not a scientist. A scientist is definitely the wrong person.

Firstly, a scientist is expecting everything to be honest and above-board. They don't know how to deal with a magician who is aiming to trick you.

So scientists are no different from the rest of us. They are easily tricked.

Secondly, there's an old saying, "You set a thief to catch a thief". Only a thief knows the tricks of a fellow professional thief. So, in trying to catch a magician, only a fellow professional magician would know what to look for, and where and when.

So back in 1973, when the TV host, Johnny Carson, invited Uri Geller onto his show to bend some spoons and metal items, he also invited James Randi along. Johnny Carson had been an amateur stage magician earlier in his career. James Randi knew that it was easy to prepare and weaken a spoon.

All you had to do was bend it back and forth many times until it got hot, and the force needed to bend the spoon suddenly decreased.

So, before Geller went on air, Randi changed all the spoons and other metal items that Geller had planned to use. Geller responded by saying that his 'power' couldn't be turned on and off like a switch, and that he simply didn't feel strong enough to try.

Mr Geller started his climb to fame with the bending spoon trick in 1972. But in 1968, a conjuring magazine had been published in Israel, and it gave "the instructions for a spoon trick that was indistinguishable from the Geller demonstration".

Uri Geller is not a psychic with supernatural powers. He's just a skilled magician, who turned a few basic magic tricks into a career.

To quote the Skeptic's Dictionary: "Geller is a fraud, he has no psychic powers, and what Geller does amounts to no more than the parlour tricks of a conjurer".

And as James Randi saidz: "If Uri Geller bends spoons with divine powers, then he's doing it the hard way".

Tags: neuroscience, pseudoscience, psychology

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Published 07 September 2010

© 2015 Karl S. Kruszelnicki Pty Ltd