TROUBLEMAKERS.(pit bulls)

One afternoon last February, Guy Clairoux picked up his two-and-a half-year-old son, Jayden, from day care and walked him back to their house in the west end of Ottawa, Ontario. They were almost home. Jayden was straggling behind, and, as his father's back was turned, a pit bull jumped over a back-yard fence and lunged at Jayden. "The dog had his head in its mouth and started to do this shake," Clairoux's wife, JoAnn Hartley, said later. As she watched in horror, two more pit bulls jumped over the fence, joining in the assault. She and Clairoux came running, and he punched the first of the dogs in the head, until it dropped Jayden, and then he threw the boy toward his mother. Hartley fell on her son, protecting him with her body. "JoAnn!" Clairoux cried out, as all three dogs descended on his wife. "Cover your neck, cover your neck." A neighbor, sitting by her window, screamed for help. Her partner and a friend, Mario Gauthier, ran outside. A neighborhood boy grabbed his hockey stick and threw it to Gauthier. He began hitting one of the dogs over the head, until the stick broke. "They wouldn't stop," Gauthier said. "As soon as you'd stop, they'd attack again. I've never seen a dog go so crazy. They were like Tasmanian devils." The police came. The dogs were pulled away, and the Clairouxes and one of the rescuers were taken to the hospital. Five days later, the Ontario legislature banned the ownership of pit bulls. "Just as we wouldn't let a great white shark in a swimming pool," the province's attorney general, Michael Bryant, had said, "maybe we shouldn't have these animals on the civilized streets."

Pit bulls, descendants of the bulldogs used in the nineteenth century for bull baiting and dogfighting, have been bred for "gameness," and thus a lowered inhibition to aggression. Most dogs fight as a last resort, when staring and growling fail. A pit bull is willing to fight with little or no provocation. Pit bulls seem to have a high tolerance for pain, making it possible for them to fight to the point of exhaustion. Whereas guard dogs like German shepherds usually attempt to restrain those they perceive to be threats by biting and holding, pit bulls try to inflict the maximum amount of damage on an opponent. They bite, hold, shake, and tear. They don't growl or assume an aggressive facial expression as warning. They just attack. "They are often insensitive to behaviors that usually stop aggression," one scientific review of the breed states. "For example, dogs not bred for fighting usually display defeat in combat by rolling over and exposing a light underside. On several occasions, pit bulls have been reported to disembowel dogs offering this signal of submission." In epidemiological studies of dog bites, the pit bull is overrepresented among dogs known to have seriously injured or killed human beings, and, as a result, pit bulls have been banned or restricted in several Western European countries, China, and numerous cities and municipalities across North America. Pit bulls are dangerous.

Of course, not all pit bulls are dangerous. Most don't bite anyone. Meanwhile, Dobermans and Great Danes and German shepherds and Rottweilers are frequent biters as well, and the dog that recently mauled a Frenchwoman so badly that she was given the world's first face transplant was, of all things, a Labrador retriever. When we say that pit bulls are dangerous, we are making a generalization, just as insurance companies use generalizations when they charge young men more for car insurance than the rest of us (even though many young men are perfectly good drivers), and doctors use generalizations when they tell overweight middle-aged men to get their cholesterol checked (even though many overweight middle-aged men won't experience heart trouble). Because we don't know which dog will bite someone or who will have a heart attack or which drivers will get in an accident, we can make predictions only by generalizing. As the legal scholar Frederick Schauer has observed, "painting with a broad brush" is "an often inevitable and frequently desirable dimension of our decision-making lives."

Another word for generalization, though, is "stereotype," and stereotypes are usually not considered desirable dimensions of our decision-making lives. The process of moving from the ...