The Science of Illusion


Most talks on the brain science of illusion feature slides or recordings, but the presentation last night at AAAS in Washington, DC, offered illustrations in four dimensions—a live performance by mesmerist Alain Nu. “The Man Who Knows” treated us to a series of experiences hard to explain but easy to enjoy. I’m going to describe a bit of what happened but you may want to just jump to the event’s video below to see for yourself, for reasons I’ll get to in a minute.

For example, Nu showed us a can of soda, popping the top, pouring soda into two ice-filled glasses, crumpling the can a bit as he invited two volunteers to quaff it down. After they had, Nu’s hands danced around the can, and its bends slowly straightened—and then it was full of soda. He popped the top, and poured more soda out, to the evident enjoyment of the two volunteers, who got a second helping. How did he do it? After his set, Nu joined three scientists who told us we’d only fooled ourselves.

“What we saw was what we always see: a simulation of reality in our minds,” said Stephen L. Macknik, a researcher at SUNY Downstate Medical Center in New York. Our brains are limited; we use a limited number of neurons to simulate reality, pulling in and combining information from eyes, memory, and other senses and regions to create an illusion of reality that we take as real. In fact, he said, “you’ve never interacted directly with the world.”

“What Alain has done is taken some of this information–which is quite sparse … and tweaked it in ways that are unexpected.”

“The brain is the magician’s confederate,” agreed fellow SUNY researcher Susana Martinez-Conde. The two also are co-authors of Sleights of Mind: What the Neuroscience of Magic Reveals About Our Everyday Deceptions and write the Illusion Chasers column for Scientific American Mind. “Our brain fills in gaps, makes assumptions”—we assume we know all about cans of soda, for example, but shown in a different light (and with a hand waving around it) do we see its shape anew?

Not only that, do we remember even what we thought we saw? Our memory of what happened is often different than what we saw happen in the moment, said Martinez-Conde, who often gets asked “how did they do that?” by people who have seen a variation of this performance. Often the way they describe the trick is so confusing that she can’t determine which illusion it was. “It would be almost impossible to reconstruct what happened from your memory,” she said. So, rather than believe what my eyes told me about that freaky soda can, you might want to check out that video.

One illusion we all subscribe to, Macknik explained, is our “perfect” field of vision. He had us use our fingers to discover what is there all along: a blind spot in our vision, where the eye “erases” the blank caused by our nose blocking the view (here’s a video example, check for yourself). “So do you have x-ray vision in your blind spot or are you blind in your blind spot?” he challenged us. The answer? “You have learned to fill things in—a blank in your vision.”

Nu described another self-experiment that fascinates him: If you sit in a semi-dark room and stare into a mirror at your face for a minute or two, your face seems to morph and change (see also an Illusion Chasers column on this effect). “The most interesting thing is not how it’s done but why it’s done,” he said. “How do we take the illusion and make it a part of our reality?”

Illusion is the sister of delusion, said panelist Richard Restak, a neurologist at George Washington University School of Medicine and Health Sciences and a longtime member of the International Brotherhood of Magicians. Restak, a prolific author and a member of the Dana Alliance for Brain Initiatives, is working on a book on delusions.

He told us of one patient he mesmerized to treat her severe neck pain, using a guided visualization involving walking and riding an elevator up and down, releasing the pain. The treatment worked—she walked out of the office not wearing her neck brace—but Restak forgot to “wake her up” from the illusion. He later got a call from her orthopedic surgeon: When he asked her how she’d gotten better, the patient told him that all Restak did was walk out of the office with her and ride up and down the elevator together. She didn’t remember it all was an illusion.

How did it work? Does it matter? For example, with the technique past-life regression, Nu said, “Hypnotists don’t care if it’s real or not because they do know it will help you.” Perhaps, like with the placebo effect, “it’s the ritual that’s important,” he said. Even words like “Just take the pill, it’s a sugar pill, it’s a placebo, but they say it will work,” and it does, he said.

What about con artists, who take our filling-the-gaps tendencies and use them to scam us? Many of the people who are calling out how con artists—from all walks of life—scam us are magicians, Macknik said. They think this is bad behavior and shouldn’t be done by anyone: magician, lawyer, doctor, salesperson, whoever. As for those of us who have fallen for cons, “yes, you should feel bad,” he said, but “you shouldn’t feel stupid. None of these [con] methods would work if your sensory systems weren’t working well.”

Nu decried the stigma that magicians are con artists. “What they really do is illustrate to you that that can really happen.” Mentalists illustrate the pleasant and entertaining aspects of it, but in the process show that the manipulation is possible and others may not be so kind. Mind-owners beware.

This event, at the American Association for the Advancement of Sciences (AAAS) in Washington, DC, was part of the Neuroscience and Society series, supported by AAAS and the Dana Foundation. Previous sessions include Stress and the Brain (story, video), Acquiring Taste and Smell (story, video), and The Science of Sleep (story, video). The program will return in the spring.

—Nicky Penttila

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