The power of learning

IN "Minority Report", a policeman, played by Tom Cruise, gleans tip-offs from three psychics and nabs future criminals before they break the law. In the real world, prediction is more difficult. But it may no longer be science fiction, thanks to the growing prognosticatory power of computers. That prospect scares some, but it could be a force for good--if it is done right. Machine learning, a branch of artificial intelligence, can generate remarkably accurate predictions.