Some years ago, a young couple came to the University of Washington to visit the laboratory of a psychologist named John Gottman. They were in their twenties, blond and blue-eyed with stylishly tousled haircuts and funky glasses. Later, some of the people who worked in the lab would say they were the kind of couple that is easy to like—intelligent and attractive and funny in a droll, ironic kind of way—and that much is immediately obvious from the videotape Gottman made of their visit. The husband, whom I’ll call Bill, had an endearingly playful manner. His wife, Susan, had a sharp, deadpan wit.

They were led into a small room on the second floor of the nondescript two-story building that housed Gottman’s operations, and they sat down about five feet apart on two office chairs mounted on raised platforms. They both had electrodes and sensors clipped to their fingers and ears, which measured things like their heart rate, how much they were sweating, and the temperature of their skin. Under their chairs, a “jiggle-o-meter” on the platform measured how much each of them moved around. Two video cameras, one aimed at each person, recorded everything they said and did. For fifteen minutes, they were left alone with the cameras rolling, with instructions to discuss any topic from their marriage that had become a point of contention. For Bill and Sue it was their dog. They lived in a small apartment and had just gotten a very large puppy. Bill didn’t like the dog; Sue did. For fifteen minutes, they discussed what they ought to do about it.

The videotape of Bill and Sue’s discussion seems, at least at first, to be a random sample of a very ordinary kind of conversation that couples have all the time. No one gets angry. There are no scenes, no breakdowns, no epiphanies. “I’m just not a dog person” is how Bill starts things off, in a perfectly reasonable tone of voice. He complains a little bit—but about the dog, not about Susan. She complains, too, but there are also moments when they simply forget that they are supposed to be arguing. When the subject of whether the dog smells comes up, for example, Bill and Sue banter back and forth happily, both with a half smile on their lips.

Sue: Sweetie! She’s not smelly . . .

Bill: Did you smell her today?

Sue: I smelled her. She smelled good. I petted her, and my hands didn’t stink or feel oily. Your hands have never smelled oily.

Bill: Yes, sir.

Sue: I’ve never let my dog get oily.

Bill: Yes, sir. She’s a dog.

Sue: My dog has never gotten oily. You’d better be careful.

Bill: No, you’d better be careful.

Sue: No, you’d better be careful. . . . Don’t call my dog oily, boy.

How much do you think can be learned about Sue and Bill’s marriage by watching that fifteen-minute videotape? Can we tell if their relationship is healthy or unhealthy? I suspect that most of us would say that Bill and Sue’s dog talk doesn’t tell us much. It’s much too short. Marriages are buffeted by more important things, like money and sex and children and jobs and in-laws, in constantly changing combinations. Sometimes couples are very happy together. Some days they fight. Sometimes they feel as though they could almost kill each other, but then they go on vacation and come back sounding like newlyweds. In order to “know” a couple, we feel as though we have to observe them over many weeks and months and see them in every state—happy, tired, angry, irritated, delighted, having a nervous breakdown, and so on—and not just in the relaxed and chatty mode that Bill and Sue seemed to be in. To make an accurate prediction about something as serious as the future of a marriage—indeed, to make a prediction of any sort—it seems that we would have to gather a lot of information and in as many different contexts as possible.

But John Gottman has proven that we don’t have to do that at all. Since the 1980s, Gottman has brought more than three thousand married couples—just like Bill and Sue—into that small room in his “love lab” near the University of Washington campus. Each couple has been videotaped, and the results have been analyzed according to something Gottman dubbed SPAFF (for specific affect), a coding system that has twenty separate categories corresponding to every conceivable emotion that a married couple might express during a conversation. Disgust, for example, is 1, contempt is 2, anger is 7, defensiveness is 10, whining is 11, sadness is 12, stonewalling is 13, neutral is 14, and so on. Gottman has taught his staff how to read every emotional nuance in people’s facial expressions and how to interpret seemingly ambiguous bits of dialogue. When they watch a marriage videotape, they assign a SPAFF code to every second of the couple’s interaction, so that a fifteen-minute conflict discussion ends up being translated into a row of eighteen hundred numbers—nine hundred for the husband and nine hundred for the wife. The notation “7, 7, 14, 10, 11, 11,” for instance, means that in one six-second stretch, one member of the couple was briefly angry, then neutral, had a moment of defensiveness, and then began whining. Then the data from the electrodes and sensors is factored in, so that the coders know, for example, when the husband’s or the wife’s heart was pounding or when his or her temperature was rising or when either of them was jiggling in his or her seat, and all of that information is fed into a complex equation.

On the basis of those calculations, Gottman has proven something remarkable. If he analyzes an hour of a husband and wife talking, he can predict with 95 percent accuracy whether that couple will still be married fifteen years later. If he watches a couple for fifteen minutes, his success rate is around 90 percent. Recently, a professor who works with Gottman named Sybil Carrère, who was playing around with some of the videotapes, trying to design a new study, discovered that if they looked at only three minutes of a couple talking, they could still predict with fairly impressive accuracy who was going to get divorced and who was going to make it. The truth of a marriage can be understood in a much shorter time than anyone ever imagined.

John Gottman is a middle-aged man with owl-like eyes, silvery hair, and a neatly trimmed beard. He is short and very charming, and when he talks about something that excites him—which is nearly all the time—his eyes light up and open even wider. During the Vietnam War, he was a conscientious objector, and there is still something of the ’60s hippie about him, like the Mao cap he sometimes wears over his braided yarmulke. He is a psychologist by training, but he also studied mathematics at MIT, and the rigor and precision of mathematics clearly moves him as much as anything else. When I met Gottman, he had just published his most ambitious book, a dense five-hundred-page treatise called The Mathematics of Divorce, and he attempted to give me a sense of his argument, scribbling equations and impromptu graphs on a paper napkin until my head began to swim.

Gottman may seem to be an odd example in a book about the thoughts and decisions that bubble up from our unconscious. There’s nothing instinctive about his approach. He’s not making snap judgments. He’s sitting down with his computer and painstakingly analyzing videotapes, second by second. His work is a classic example of conscious and deliberate thinking. But Gottman, it turns out, can teach us a great deal about a critical part of rapid cognition known as thin-slicing. “Thin-slicing” refers to the ability of our unconscious to find patterns in situations and behavior based on very narrow slices of experience. When Evelyn Harrison looked at the kouros and blurted out, “I’m sorry to hear that,” she was thin-slicing; so were the Iowa gamblers when they had a stress reaction to the red decks after just ten cards.