Not long ago, one of the world’s top tennis coaches, a man named Vic Braden, began to notice something strange whenever he watched a tennis match. In tennis, players are given two chances to successfully hit a serve, and if they miss on their second chance, they are said to double-fault, and what Braden realized was that he always knew when a player was about to double-fault. A player would toss the ball up in the air and draw his racket back, and just as he was about to make contact, Braden would blurt out, “Oh, no, double fault,” and sure enough, the ball would go wide or long or it would hit the net. It didn’t seem to matter who was playing, man or woman, whether he was watching the match live or on television, or how well he knew the person serving. “I was calling double faults on girls from Russia I’d never seen before in my life,” Braden says. Nor was Braden simply lucky. Lucky is when you call a coin toss correctly. But double-faulting is rare. In an entire match, a professional tennis player might hit hundreds of serves and double-fault no more than three or four times. One year, at the big professional tennis tournament at Indian Wells, near Braden’s house in Southern California, he decided to keep track and found he correctly predicted sixteen out of seventeen double faults in the matches he watched. “For a while it got so bad that I got scared,” Braden says. “It literally scared me. I was getting twenty out of twenty right, and we’re talking about guys who almost never double-fault.”

Braden is now in his seventies. When he was young, he was a world-class tennis player, and over the past fifty years, he has coached and counseled and known many of the greatest tennis players in the history of the game. He is a small and irrepressible man with the energy of someone half his age, and if you were to talk to people in the tennis world, they’d tell you that Vic Braden knows as much about the nuances and subtleties of the game as any man alive. It isn’t surprising, then, that Vic Braden should be really good at reading a serve in the blink of an eye. It really isn’t any different from the ability of an art expert to look at the Getty kouros and know, instantly, that it’s a fake. Something in the way the tennis players hold themselves, or the way they toss the ball, or the fluidity of their motion triggers something in his unconscious. He instinctively picks up the “giss” of a double fault. He thin-slices some part of the service motion and—blink!—he just knows. But here’s the catch: much to Braden’s frustration, he simply cannot figure out how he knows.

“What did I see?” he says. “I would lie in bed, thinking, How did I do this? I don’t know. It drove me crazy. It tortured me. I’d go back and I’d go over the serve in my mind and I’d try to figure it out. Did they stumble? Did they take another step? Did they add a bounce to the ball—something that changed their motor program?” The evidence he used to draw his conclusions seemed to be buried somewhere in his unconscious, and he could not dredge it up.

This is the second critical fact about the thoughts and decisions that bubble up from our unconscious. Snap judgments are, first of all, enormously quick: they rely on the thinnest slices of experience. But they are also unconscious. In the Iowa gambling experiment, the gamblers started avoiding the dangerous red decks long before they were actually aware that they were avoiding them. It took another seventy cards for the conscious brain to finally figure out what was going on. When Harrison and Hoving and the Greek experts first confronted the kouros, they experienced waves of repulsion and words popping into their heads, and Harrison blurted out, “I’m sorry to hear that.” But at that moment of first doubt, they were a long way from being able to enumerate precisely why they felt the way they did. Hoving has talked to many art experts whom he calls fakebusters, and they all describe the act of getting at the truth of a work of art as an extraordinarily imprecise process. Hoving says they feel “a kind of mental rush, a flurry of visual facts flooding their minds when looking at a work of art. One fakebuster described the experience as if his eyes and senses were a flock of hummingbirds popping in and out of dozens of way stations. Within minutes, sometimes seconds, this fakebuster registered hosts of things that seemed to call out to him, ‘Watch out!’”

Here is Hoving on the art historian Bernard Berenson. “[He] sometimes distressed his colleagues with his inability to articulate how he could see so clearly the tiny defects and inconsistencies in a particular work that branded it either an unintelligent reworking or a fake. In one court case, in fact, Berenson was able to say only that his stomach felt wrong. He had a curious ringing in his ears. He was struck by a momentary depression. Or he felt woozy and off balance. Hardly scientific descriptions of how he knew he was in the presence of something cooked up or faked. But that’s as far as he was able to go.”

Snap judgments and rapid cognition take place behind a locked door. Vic Braden tried to look inside that room. He stayed up at night, trying to figure out what it is in the delivery of a tennis serve that primes his judgment. But he couldn’t.

I don’t think we are very good at dealing with the fact of that locked door. It’s one thing to acknowledge the enormous power of snap judgments and thin slices but quite another to place our trust in something so seemingly mysterious. “My father will sit down and give you theories to explain why he does this or that,” the son of the billionaire investor George Soros has said. “But I remember seeing it as a kid and thinking, At least half of this is bull. I mean, you know the reason he changes his position on the market or whatever is because his back starts killing him. He literally goes into a spasm, and it’s this early warning sign.”

Clearly this is part of the reason why George Soros is so good at what he does: he is someone who is aware of the value of the products of his unconscious reasoning. But if you or I were to invest our money with Soros, we’d feel nervous if the only reason he could give for a decision was that his back hurt. A highly successful CEO like Jack Welch may entitle his memoir Jack: Straight from the Gut, but he then makes it clear that what set him apart wasn’t just his gut but carefully worked-out theories of management, systems, and principles as well. Our world requires that decisions be sourced and footnoted, and if we say how we feel, we must also be prepared to elaborate on why we feel that way. This is why it was so hard for the Getty, at least in the beginning, to accept the opinion of people like Hoving and Harrison and Zeri: it was a lot easier to listen to the scientists and the lawyers, because the scientists and the lawyers could provide pages and pages of documentation supporting their conclusions. I think that approach is a mistake, and if we are to learn to improve the quality of the decisions we make, we need to accept the mysterious nature of our snap judgments. We need to respect the fact that it is possible to know without knowing why we know and accept that—sometimes—we’re better off that way.

Imagine that I’m a professor, and I’ve asked you to come and see me in my office. You walk down a long corridor, come through the doorway, and sit down at a table. In front of you is a sheet of paper with a list of five-word sets. I want you to make a grammatical four-word sentence as quickly as possible out of each set. It’s called a scrambled-sentence test. Ready?

01 him was worried she always

02 from are Florida oranges temperature