Science News - April 25, 2009

Magicians often rely on misdirection — getting the audience to look to the wrong place while the performer pockets the dove or switches a live fish for a fake. By carefully controlling the audience’s gaze and using gestures to draw focus away from the trick, a magician can force spectators to look away, too.

Macknik explains a classic trick called the French Drop to illustrate this point. A magician holds a coin in the left hand and pretends to pass the coin to the right hand, which remains empty. “What’s critical is that the magician looks at the empty hand. He pays riveted attention to the hand that is empty,” Macknik says. The audience takes its cue from the magician and focuses attention on the right hand, believing it to hold the coin.

Controlling where spectators move their eyes takes skill. Perhaps more impressive, though, is controlling spectators’ minds. Several experiments have now shown that people can stare directly at something and not see it.

For a study published in Current Biology in 2006, Kuhn and his colleagues tracked where people gazed as they watched a magician throw a ball into the air several times. On the last throw, the magician only pretended to toss the ball. Still, spectators claimed to have seen the ball launch and then miraculously dis-

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appear in midair. But here’s the trick: In most cases, subjects kept their eyes on the magician’s face or on the ball, which never left his hand. Only when the ball was actually at the top part of the screen did participants look there. Yet the brain perceived the ball in the air, overriding the actual visual information: The brains, not the eyes, were fooled.

Understanding how magicians carry off tricks by manipulating perception begs the question of whether their success depends on some people being less perceptive. (And, alternatively, of whether there really are tough crowds.) Researchers trying to answer that question get only one shot: Once the ball in the magician’s hand is pointed out, it’s impossible to miss. “The tough part with studying inattentional blindness, and with magic, is that you can only do it once,” says Daniel Simons of the University of Illinois at Urbana-Champaign.

Simons and his colleagues found a way around this problem by first measuring how perceptive people are. Then the team asked whether more perceptive people succumb less easily to inattentional blindness, which is when a person doesn’t perceive something because the mind, not the eyes, wanders. In a paper in the April Psychonomic Bulletin & Review, the researchers report that people who are very good at paying attention had no advantage in performing a visual task that required noticing something unexpected. Task difficulty was what mattered. Few participants could spot a more subtle change, while most could spot an easy one. The results suggest that magicians may be tapping in to some universal property of the human brain.

“We’re good at focusing attention,” says Simons. “It’s what the visual system was built to do.” Inattentional blindness, he says, is a by-product, a necessary consequence, of our visual system allowing us to focus intently on a scene.

Magical experiments

Magicians have perfected their tricks over the millennia. So the techniques magicians use on stage, says Macknik, are “exceptionally robust,” which, in neuro-

scientists’ lingo is very high praise for a strong effect. “Cognitive neuroscience’s experiments are really crappy compared to magicians’,” he says. In his experience, subjects often guess what the experiment is about, which ruins the experiment.

There’s another reason the tricks up magicians’ sleeves may prove more powerful than anything dreamed up in a lab. Many classic visual attention experiments completely ignore social context, something known to affect attention and perception and long exploited by magicians.

Martinez-Conde and Macknik plan to study the effects of one aspect of social context — laughter — on attention. Magicians like Mac King have the audience in stitches throughout a performance. Martinez-Conde says one of her collaborators, magician John Thompson, told her that when the audience is laughing, time stops, giving the magician a golden opportunity to act unnoticed.

Understanding how emotional states can affect perception and attention may lead to more effective ways to treat people who have attention problems.

“Scientifically, that can tell us a lot about the interaction between emotion and attention, of both the normally functioning brain and what happens in a diseased state,” says Martinez-Conde.

Channeling attention within different settings — such as a hospital rehabilitation unit or a classroom of unruly fifth graders —is one lofty aim of this new marriage between magicians and neuroscientists. “Here we can take methods from magicians,” Macknik says, and find new ways to treat people who have brain trauma, Alzheimer’s disease and attention-deficit/hyperactivity disorder. “We don’t know how it’s going to work because no one’s ever done it before.”

He expects that the study of consciousness and the mind will benefit enormously from teaming up with magicians. “We’re just at the beginning,” Macknik says. “It’s been very gratifying so far, but it’s only going to get better.” s