Collection 2: "Magic and the Brain" by Susana Martinez-Conde and Stephen L. Macknik

The trick and its explanation by John Thompson (aka the Great Tomsoni) reveal a deep intuitive understanding of the neural processes taking place in the spectators’ brains—the kind of understanding that we neuroscientists can appropriate for our own scientific benefit.

The more they stare at her, the less they notice the hidden devices in the floor, and the better adapted their retinal neurons become to the brightness of the light and the color they perceive.

All during Thompson’s patter after his little “joke,” each spectator’s visual system is undergoing a brain process called neural adaptation.

All during Thompson’s patter after his little “joke,” each spectator’s visual system is undergoing a brain process called neural adaptation.

All during Thompson’s patter after his little “joke,” each spectator’s visual system is undergoing a brain process called neural adaptation.

The responsiveness of a neural system to a constant stimulus (as measured by the firing rate of the relevant neurons) decreases with time.

An illusion created by an image like this one often induces a false sense of flowing movement in the concentric rings...

An illusion created by an image like this one often induces a false sense of flowing movement in the concentric rings...

Second, Thompson performs the real trick only after the audience thinks it is already over. That gains him an important cognitive advantage—the spectators are not looking for a trick at the critical moment, and so they slightly relax their scrutiny.

Second, Thompson performs the real trick only after the audience thinks it is already over. That gains him an important cognitive advantage—the spectators are not looking for a trick at the critical moment, and so they slightly relax their scrutiny.

They manipulate the focus and intensity of human attention, controlling, at any given instant, what we are aware of and what we are not. They do so in part by employing bewildering combinations of visual illusions (such as afterimages), optical illusions (smoke and mirrors), special effects (explosions, fake gunshots, precisely timed lighting controls), sleight of hand, secret devices and mechanical artifacts (“gimmicks”).

They manipulate the focus and intensity of human attention, controlling, at any given instant, what we are aware of and what we are not. They do so in part by employing bewildering combinations of visual illusions (such as afterimages), optical illusions (smoke and mirrors), special effects (explosions, fake gunshots, precisely timed lighting controls), sleight of hand, secret devices and mechanical artifacts (“gimmicks”).

But the most versatile instrument in their bag of tricks may be the ability to create cognitive illusions. Like visual illusions, cognitive illusions mask the perception of physical reality.

Yet unlike visual illusions, cognitive illusions are not sensory in nature.

Rather they involve high-level functions such as attention, memory and causal inference. With all those tools at their disposal, well-practiced magicians make it virtually impossible to follow the physics of what is actually happening—leaving the impression that the only explanation for the events is magic.

Rather they involve high-level functions such as attention, memory and causal inference. With all those tools at their disposal, well-practiced magicians make it virtually impossible to follow the physics of what is actually happening—leaving the impression that the only explanation for the events is magic.

Neuroscientists are just beginning to catch up with the magician’s facility in manipulating attention and cognition.

Of course the aims of neuroscience are different from those of magic, the neuroscientist seeks to understand the brain and neuron underpinnings of cognitive functions, whereas the magician wants mainly to exploit cognitive weaknesses.

Neuroscience is becoming familiar with the methods of magic by subjecting magic itself to scientific study—in some cases showing for the first time how some of its methods work in the brain.

Many studies of magic conducted so far confirm what is known about cognition and attention from earlier work in experimental psychology. A cynic might dismiss such efforts: Why do yet another study that simply confirms what is already well known?

By applying the tools of magic, neuroscientists can hope to learn how to design more robust experiments and to create more effective cognitive and visual illusions for exploring the neural bases of attention and awareness.

Magicians use the general term “misdirection” to refer to the practice of diverting the spectator's attention away from a secret action. In the lingo of magic, misdirection draws the audience's attention toward the “effect” and away from the “method,” the secret behind the effect.

Borrowing some terms from cognitive psychology, we have classified misdirection as “overt” and “covert.” The misdirection is overt if the magician redirects the spectator's gaze away from the method—perhaps simply by asking the audience to look at a particular object.

“Covert” misdirection, in contrast, is a subtler technique; there, too, the magician draws the spectator's attentional spotlight—or focus of suspicion—away from the method, but without necessarily redirecting the spectator's gaze. Under the influence of covert misdirection, spectators may be looking directly at the method behind the trick yet be entirely unaware of it.

When event A precedes event B, we often conclude, rightly or wrongly, that A causes B. The skilled magician takes advantage of that predisposition by making sure that event A (say, pouring water on a ball) always precedes event B (the ball disappearing).