A lot of people don't like magic because it make them feel stupid, but in reality getting fooled by magic tricks says little about your intelligence. You can easily outsmart someone who is smarter than you, and our susceptibility to magic and illusions is poorly correlated with IQ. As the British mentalist Ian Rowland once wrote, "A rocket scientist can be fooled by a deceiver, because she knows about rocket science and not deception."
Indeed, the annals of science are replete with accounts of brilliant professors shamelessly taken in by dime-store swindles. Back in the seventies, metal-bender Uri Geller pulled the wool over the eyes of a labful of Ph.D.s using sleights-of-hand a fourth grader could carry out. When asked if he thought folks like Geller were the real deal, physicist Richard Feynman once replied, "I'm smart enough to know that I'm dumb."
Unlike Geller, I do in fact possess psychic powers and to prove it to you I'm going to predict the exact difference in the amount of pocket change we are both carrying. All I need you to do is remove some change from your purse or your pocket -- not more than a couple of bucks, to keep this short -- and hold it in your fist. Shake it around a bit so I can feel the vibrations. Excellent. I am definitely getting a reading now, more than I had hoped for in fact. My sixth sense is telling me three things: that I have as much change as you do, plus two extra quarters, and enough left over to bring your total up to $2.35. You look skeptical. Lay your change on the table and count it. Great. Now since we are doing this remotely, you'll have to be my stunt double. Reaching in my pocket it appears I have ten quarters, two dimes, a pair of nickels, and five pennies -- totaling $2.85. (I was going to do laundry later.) I want you to pretend my pile of change is on the table next to yours -- or even better, procure this array of coins for yourself and do it for real. Now I predicted my pile would contain exactly as much as yours plus two quarters, so please remove from my pile the exact amount you were carrying in your pocket, plus an additional two quarters, and set this amount aside. I also predicted that what remained in my pile would be exactly enough to bring your total up to $2.35, so push the rest of my coins into your pile, merging the two, and add them all up. Was I right? I told you I was psychic!
If you were fooled by this trick you're in good company, because so was Albert Einstein, when British mentalist Al Koran (real name: Edward Doe) performed it for him at a dinner club. The secret is all in the wording. Initially, I said I was going to predict the difference in the amount of change we were carrying, but that was not what I ended up doing, though it might have appeared so. I spun this equivocation by claiming I would make three predictions, as though that were somehow better. In truth, my three predictions, taken together, were logically equivalent to the statement: "I have $2.85." To see why, let's call the amount of change in your pocket X. I started with $2.85 and removed an amount equal to X from my pile, along with two quarters, leaving me with $2.85 - 0.50 - X = $2.35 - X. We then took this remainder and added it to your pile (X). You don't have to be Einstein to realize that:
$2.35 - X
After Koran fooled Herr Einstein twice with this trick -- which, by the way, makes for a great bar bet -- he took pity on the physicist. "It's not the numbers, but the words that fooled you," he said. A victim of his own expectations, Einstein assumed a sophisticated mathematical principle was involved when in fact a simple grammatical swindle had laid him low.
As The Trick That Fooled Einstein illustrates, intelligence and experience can sometimes blind us to the obvious. Indeed, many expert magicians will tell you that some of the hardest people to fool are children. "I'd rather have an audience full of Ph.D.s than an audience full of children," magician skeptic James Randi once told me. "Scientists are easier to deceive because they're so well educated. They're educated in a universe that behaves itself, not a universe that lies to them. I'd rather do a card trick for a scientist than a kid any day. Kids aren't smart enough to be fooled."
As adults, we carry around a matrix of unconscious assumptions that lend structure and stability to our lives, but which can also anchor us to a ruinous logic -- kind of like how seatbelts are a great idea until they trap you inside a burning vehicle. By contrast, the young mind is largely untethered to preconceptions about how the world works.
My all time favorite forest-for-the-trees story involves the philosopher of language J. L. Austin, a very proper Oxford Don who spent his life thinking about speech. In the prime of his career, Austin gave a talk in which he asserted that while a double negative in English always has a positive connotation (as in, "I don't disagree"), in no language does a double positive have a negative meaning -- at which point the quick-witted New York City philosopher Sidney Morgenbesser blurted out: "Yeah, yeah."