A TV commercial posted online shows an English magician named Dynamo apparently levitating off the side of one of London's iconic double-decker buses, as amazed onlookers gape, point, and, because this is 2013, shoot photos and video with their phones. He then slides off the bus, produces a can of Pepsi Max, opens it, and takes a sip.
It was posted on Monday, and by Thursday afternoon, it already had more than 2.3 million views. Have a look at the video at the top of this page, if you haven't done so already.
"If you can just take a moment to look at things from a new perspective," says Dynamo in his gentle Yorkshire accent, "you might see the world in a whole new light."
So how did Dynamo do it? Here, we reveal his secret: He had the soda can in his pocket the whole time.
OK, we're not going to say how Dynamo floated alongside the bus: Exposing the secrets of individual magicians serves only to diminish the entertainment. (It can also ruin their livelihoods, and why would we want to do that?)
So instead, we'll just give away how every magician everywhere performs every illusion. And we'll share some cognitive psychology with you along the way.
At the heart of every illusion is misdirection, the manipulation of the audience's attention.
"Everyone knows what attention is," wrote William James in his seminal 1890 work, "Principles of Psychology."
"It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others, and is a condition which has a real opposite in the confused, dazed, scatterbrained state which in French is called distraction, and Zerstreutheit in German."
And skilled magicians are the ultimate Zerstreutheitmeisters. Gesturing hands, shiny props, dazzling spotlights, flying doves, "assistants" in sparkly outfits, and, in Dynamo's case, waggling feet and a smartphone are all expertly deployed to take your mind off of where the "magic" – usually a fairly straightforward mechanism – is really happening. And we fall for it almost every time.
We get fooled for two big reasons: The first is that we aren't able to take in all of the stimuli in our environment all at once. You might think that you're eyes are merely windows to the outside world, but the picture that you're seeing right now is mostly a simulation. As you focus your attention on these words, the rest your visual field is sketched out in only the barest detail. It only appears like a rich vista because your brain is constantly filling in the gaps, not with what it actually perceives, but with what it expects to perceive.
Want proof? Place your left hand over your left eye. Extend your right arm forward, with your index finger raised. Now, staring at a point straight ahead, and not at your finger, slowly move your arm to the right. When your arm is at an angle of about 15 degrees, the tip of your finger will vanish. Presto!
This happens because of a human blind spot, the point at which the optic nerve attaches to the retina. There are no photoreceptors on that part of the eye. But most of us are never aware that we have a pair of empty spots hovering right in front of us. Your brain just fills in the gap with whatever is in the background. You see what you expect to see.
Magicians don't usually exploit this physiological blind spot, but they exploit our cognitive blind spots all the time. For instance, you watch as a conjurer appears to pass a coin from the right hand to the left. Your attention, honed by thousands of generations of your rock-throwing forbears, leads the target, missing the sleight. You're surprised when the magician reveals the left hand to be empty. Then, while you're looking at the left hand, you fail to notice the right hand slipping the coin into a pocket. The human mind naturally assumes that the background, that is, everything but the empty hand that you're staring at, remains static.
The other big reason that we are so easily fooled by magicians is that humans are intensely social animals. In 1969, the psychologist Stanley Milgram conducted an experiment in New York City that involved volunteers staring up at the sky, gazing at nothing in particular. With one person looking up, about one in 25 passers by also looked up. When five people looked up, about one in five followed suit. As the number of upward-gazing volunteers grew, so did the upward-gazing passers-by. Milgram described this behavior as a "contagion."
Magicians are masters of contagious attention. A paper published in the journal Current Biology in 2006 had subjects watch the Vanishing Ball illusion, a simple trick in which the magician tosses a ball in the air a few times, only to have it apparently vanish in midair:
In the final "toss," the ball actually remains in the magician's hand. But our attention follows the gaze of the magician. When the magician's gaze followed the trajectory of the toss, more than two thirds of the subjects said they saw a ball where there wasn't one. Most even suspected that there was someone at the top of the screen catching the ball. But when the magician looked straight ahead, only a third were fooled. It's the social cues, not the sleight-of-hand, that makes the trick work.
The subjects had cameras tracking their eyes. Interestingly, the researchers found that the observers eyes only followed the actual tosses, not the imaginary one. It wasn't their eyes that were fooled. It was their minds.
So the next time you attend a magic show, here's how to see through the illusions. First, keep an eye on the magician's other hand, the one that doesn't seem to be doing anything interesting. Second, never look where the magician is looking.
Or better still, don't. Just sit back enjoy the show. After all, you paid money to be entertained, not disillusioned.
[Editor's note of full disclosure: The writer's mother is a magician, thus his reluctance to completely spill professional secrets].