Sleights of Mind - The Science of Magic

As he ran through the trick a second time, annotating each step, we saw how we had been led to mismatch cause and effect, to form one false hypothesis after another. Sometimes the coins were coming from his right hand, and sometimes from his left, hidden beneath the fingers holding the bucket.

He left us with his definition of magic: "The theatrical linking of a cause with an effect that has no basis in physical reality, but that - in our hearts - ought to."

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In his opening address, Michael Gazzaniga, the president of the consciousness association, had described another form of prestidigitation - a virtual reality experiment in which he had put on a pair of electronic goggles that projected the illusion of a deep hole opening in what he knew to be a solid concrete floor. Jolted by the adrenaline rush, his heart beat faster and his muscles tensed, a reminder that even without goggles the brain cobbles together a world from whatever it can.

"In a sense our reality is virtual," Dr. Gazzaniga said. "Think about flying in an airplane. You're up there in an aluminum tube, 30,000 feet up, going 600 miles an hour, and you think everything is all right."

Dr. Gazzaniga is famous for his work with split-brain patients, whose left and right hemispheres have been disconnected as a last-ditch treatment for severe epilepsy. These are the experiments that have led to the notion, oversimplified in popular culture, that the left brain is predominantly analytical while the right brain is intuitive and laid-back.

The left brain, as Dr. Gazzaniga put it, is the confabulator, constantly concocting stories. But mine was momentarily dumbstruck when, after his talk, I passed through a doorway inside the Venetian Resort Hotel Casino and entered an air-conditioned simulation of the Grand Canal. My eyes were drawn upward to the stunning illusion of a trompe l'oeil sky and what I decided must be ravens flying high overhead. Looking closer, my brain discarded that theory, and I saw that the black curved wings were the edges of discs - giant thumbtacks holding up the sky. Later I was told they were automatic sprinklers, in case the clouds catch fire.

"It's 'The Truman Show,' " said Robert Van Gulick, a philosopher at Syracuse University, as I joined him at a table overlooking a version of the Piazza San Marco. A sea breeze was wafting through the window, the clouds were glowing in the late afternoon sun (and they were still glowing, around 10:30 p.m., when I headed back toward my hotel). How could we be sure that the world outside the Venetian - outside Las Vegas itself - wasn't also a simulation? Or that I wasn't just a brain in a vat in some mad scientist's laboratory.

Dr. Van Gulick had come to the conference to talk about qualia, the raw, subjective sense we have of colors, sounds, tastes, touches and smells. The crunch of the crostini, the slitheriness of the penne alla vodka - a question preoccupying philosophers is where these personal experiences fit within a purely physical theory of the mind.

Like physicists, philosophers play with such conundrums by engaging in thought experiments. In a recent paper, Michael P. Lynch, a philosopher at the University of Connecticut, entertained the idea of a "phenomenal pickpocket," an imaginary creature, like Apollo the thief, who distracts your attention while he removes your qualia, turning you into what's known in the trade as a philosophical zombie. You could catch a ball, hum a tune, stop at a red light - act exactly like a person but without any sense of what it is like to be alive. If zombies are logically possible, some philosophers insist, then conscious beings must be endowed with an ineffable essence that cannot be reduced to biological circuitry.

Dr. Lynch's fantasy was a ploy to undermine the zombie argument. But if zombies do exist, it is probably in Las Vegas. One evening as I walked across the floor of the Imperial Palace casino - a cacophony of clanging bells and electronic arpeggios - it was easy to imagine that the hominids parked in front of the one-armed bandits were simply extensions of the machines.

"Intermittent conditioning," suggested Irene Pepperberg, an adjunct associate professor at Brandeis University who studies animal intelligence. If you want to train a laboratory rat to pull a crank to get a food pellet, the reflex will be scratched in deeper if the creature is rewarded with some regularity but not all the time.