This does not mean that our inner psychological states and personal histories are not important in explaining our behavior. An enormous percentage of those who engage in violent acts, for example, have some kind of psychiatric disorder or come from deeply disturbed backgrounds. But there is a world of difference between being inclined toward violence and actually committing a violent act. A crime is a relatively rare and aberrant event. For a crime to be committed, something extra, something additional, has to happen to tip a troubled person toward violence, and what the Power of Context is saying is that those Tipping Points may be as simple and trivial as everyday signs of disorder like graffiti and fare-beating. The implications of this idea are enormous. The previous notion that disposition is everything — that the cause of violent behavior is always "sociopathic personality" or "deficient superego" or the inability to delay gratification or some evil in the genes — is, in the end, the most passive and reactive of ideas about crime. It says that once you catch a criminal you can try to help him get better — give him Prozac, put him in therapy, try to rehabilitate him — but there is very little you can do to prevent crime from happening in the first place. The old understanding of handling crime epidemics leads inevitably to a preoccupation with defensive measures against crime. Put an extra lock on the door, to slow the burglar down and maybe encourage him to go next door. Lock up criminals for longer, so that they have less opportunity to do the rest of us harm. Move to the suburbs, to put as much distance as possible between yourself and the majority of criminals.

Once you understand that context matters, however, those specific and relatively small elements in the environment can serve as Tipping Points, that defeatism is turned upside down. Environmental Tipping Points are things that we can change: we can fix broken windows and clean up graffiti and change the signals that invite crime in the first place. Crime can be more than understood. It can be prevented. There is a broader dimension to this. Judith Harris has convincingly argued that peer influence and community influence are more important than family influence in determining how children turn out. Studies of juvenile delinquency and high school drop-out rates, for example, demonstrate that a child is better off in a good neighborhood and a troubled family than he or she is in a troubled neighborhood and a good family. We spend so much time celebrating the importance and power of family influence that it may seem, at first blush, that this can't be true. But in reality it is no more than an obvious and commonsensical extension of the Power of Context, because it says simply that children are powerfully shaped by their external environment, that the features of our immediate social and physical world — the streets we walk down, the people we encounter — play a huge role in shaping who we are and how we act. It isn't just serious criminal behavior, in the end, that is sensitive to environmental cues, it is all behavior. Weird as it sounds, if you add up the meaning of the Stanford prison experiment and the New York subway experiment, they suggest that it is possible to be a better person on a clean street or in a clean subway than in one littered with trash and graffiti.

"In a situation like this, you're in a combat situation," Goetz told his neighbor Myra Friedman, in an anguished telephone call just days after the shooting. "You're not thinking in a normal way. Your memory isn't even working normally. You are so hyped up. Your vision actually changes. Your field of view changes. Your capabilities change. What you are capable of changes." He acted, Goetz went on, "viciously and savagely… If you corner a rat and you are about to butcher it, okay? The way I responded was viciously and savagely, just like that, like a rat."

Of course he did. He was in a rat hole.

FIVE

The Power of Context (Part Two)

THE MAGIC NUMBER ONE HUNDRED AND FIFTY

In 1996, a sometime actress and playwright by the name of Rebecca Wells published a book entitled Divine Secrets of the Ya-Ya Sisterhood. Its arrival in the bookstores was not a major literary event. Wells had written one previous book — Little Altars Everywhere — which had been a minor cult hit in and around her hometown of Seattle. But she was not Danielle Steel or Mary Higgins Clark. When Wells gave a reading soon after her book was published in Greenwich, Connecticut, there were seven people in the audience. She had a smattering of reviews here and there, mostly positive, and in the end her book sold a very respectable 15,000 copies in hardcover.

A year later, Ya-Ya Sisterhood came out in paperback. The first edition of 18,000 copies sold out in the first few months, exceeding expectations. By early summer, total paperback sales had reached 30,000, and both Wells and her editor began to get the sense that something strange and wonderful was about to happen. "I'd be signing books and there would be groups of women who would come together — six or seven women — and they would have me sign anywhere between three and ten books," Wells remembered later. Wells's editor, Diane Reverand, went to her marketing people and said it was time for an advertising campaign. They bought one ad, opposite the contents page of the New Yorker magazine, and in the space of a month sales doubled to 60,000. Going from one reading to the next, across the country. Wells began to see changes in the composition of her audience. "I started noticing mothers and daughters coming. The daughters would be in their late thirties, early forties. The mothers were of the generation who went to high school during World War Two. Then I noticed that there started to be three generations coming, twenty somethings as well. And then, to my total delight — and this didn't happen until later — there would be teenagers and fifth-graders.''

Divine Secrets of the Ya-Ya Sisterhood was not yet on the bestseller lists. That wouldn't happen until February 1998, when it would hit the charts and stay there, through 48 printings and 2.5 million copies. The national media attention — the articles in the big women's magazines and the appearance on television shows that would turn Wells into a celebrity — hadn't started yet either. But through the power of word-of-mouth, her book had tipped. "The turning point for me was probably in northern California, the winter after the paperback came out," Wells said. "I walked into a situation where all of a sudden there were seven hundred and eight hundred people at my readings."

Why did Ya-Ya Sisterhood turn into an epidemic? In retrospect, the answer seems fairly straightforward. The book itself is heartwarming and beautifully written, a compelling story of friendship and mother-daughter relationships. It spoke to people. It's sticky. Then there's the fact that Wells herself is an actress. She didn't read from her novel as she traveled across the country so much as she acted it out, playing each character with such skill that she turned her readings into performances. Wells is a classic Salesman. But there is a third, less obvious, factor here, which has to do with the last of the principles of epidemics. The success of Ya-Ya is a tribute to the Power of Context. More specifically, it is testimony to the power of one specific aspect of context, which is the critical role that groups play in social epidemics.

In a way, this is an obvious observation. Anyone who has ever been to the movies knows that the size of the crowd in the theater has a big effect on how good the movie seems: comedies are never funnier and thrillers never more thrilling than in a packed movie house. Psychologists tell us much the same thing: that when people are asked to consider evidence or make decisions in a group, they come to very different conclusions than when they are asked the same questions by themselves. Once we're part of a group, we're all susceptible to peer pressure and social norms and any number of other kinds of influence that can play a critical role in sweeping us up in the beginnings of an epidemic.