Mind and Magic

Dec 08 2015

In Sleights of Mind, the authors cannily explain some of the latest science of the brain though examples of magic tricks, illusions and mind games that demonstrate the fallibilities of the human mind and the way in which magicians often have greater insight into the innermost workings of our brain than most neuroscientists.

They start with visual perception, showing as many other have, that there is so often a gap between what we perceive and what is really out there in the world. This gap is caused by the way in which the brain constructs reality, where what we all see, hear, feel and think very much depends on what we expect to see, hear, feel and think. Our past experiences and memories (which are fallible as we see later), shape our expectations of what will happen much more than we realise and often much more than real events influence what we experience. What we experience mostly depends on what has been “useful” for us to experience on previous occasions.

Often it’s the everyday cue that help us decipher the world, that play tricks with us when they are manipulated by magicians. For example, we use occlusion (the covering of an object by something in front of it) and perspective (the way in which objects and lines recede towards a central point the further away they are) in order to perceive depth and distance. Magicians are able to use these cues to deceive us into believing that we “really” see something that is not actually there. So a playing card that is partially hiding another playing card in a magician’s hand must be closer to you, right? Sometimes wrong, as a magician may look like he is placing a card behind others or in the middle of the deck, but is he really putting it there?


Similarly, the bending spoon trick depends on the fact that we expect objects to be whole and to look as they normally do in terms of shape and size, so when someone plays with multiple bent spoons in their hands, they become multiple whole and untampered spoons. The laws of Gestalt show that we are more likely to see the whole picture as it normally looks (the law of good continuation, or amodal completion), than to break up scenes into their little pieces, which if a magician is involved may not be quite so wholesome.

Magicians also use the different qualities of our central and peripheral vision. Our peripheral vision is more attuned to overall patterns and structure (as well as movement) than our central vision. These different aspects of our visual perception are very important in the cues of contrast that we use to identify different objects and more importantly people. Research has shown that one of the big differences (and important cues) in differentiating men from women is that female faces tend to have more contrast than males, and the amount of contrast can be used to make a female face look more male, or vice-versa.

The brain integrates multiple cues, including those from different senses, in interpreting the world and what is happening around us. If you see a bright light and hear a loud sound, your brain automatically associates the two events, even if they are unrelated. What a food sounds like can influence its taste (see here), and this goes for the interaction between sound and your skin. In a fascinating experiment, researchers delivered puffs of air to people’s ankles and played the sounds pa and ta.  However, when the sounds were played without the puffs, they were more likely to be heard as ba and da.

This is similar to the McGurk effect that is better known, and demonstrates that we should be wary of when a magician taps the table or bangs his hat, as the real excitement may be happening somewhere else or sometime else. Ventriloquists rely on the fact that we correlate the sounds we hear with the mouth we see moving, and cinemas use the same trick to make it seem as though words come from the actors mouths when they are actually coming from the speakers behind you.

Magicians sometimes rely on the fallibility of memory and the use of misinformation to create mental confabulations of what we have experienced. This is not quite the same as implanting memories in Inception, but it is surprising and concerning how easily even small words and phrases can reshape the way we remember an experience. When asked about the speed at which a car “hit” or “smashed into”  another car, observers gave faster estimates for the first than the second, Similarly, magicians manipulate our minds by implanting the right words and phrases into their patter.

Ultimately the mind is a prediction machine, and that makes it very easy to manipulate as once it thinks it knows what to expect it tends to take the easy option and stop looking at alternatives. When a magician tosses a ball (or other object) into space yet another time, you expect it to follow the same trajectory that it did on the previous occasions, even if he has actually slipped it into his other hand. There is also some manipulation of your gaze involved in this trick, to make sure you look in the right places at the right times (even from the bob of the magician’s head which we are inclined to follow as fellow humans).

Ultimately, much of this trickery relies on the brain’s focus on cause and effect and the way in which expectations are so important in making the world an orderly and predictable place. Magicians know this and rely on it to make us see, hear, feel and think what should be there, but what they have made sure is not. For a while they make us see what we want to see, because that’s what they want us to see too, rather than the truth for what it really is. Like much in art and culture, magic is all about the element of surprise and the breaking of expectations, and that’s why we love to watch.

REFERENCE
Sleights of Mind: What the neuroscience of magic reveals about our everyday deceptions by Macknik & Martinez-Conde

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