But we also have some more direct evidence for the idea that children learn like scientists. Alison and Virginia Slaughter, one of her students, looked at three-year-old children who didn't yet fully understand belief—children who still said they had always thought that there were pencils in the candy box. Then, over the course of a few weeks, Virginia gave the children systematic evidence that their predictions were false. She told them firmly that they hadn't said pencils at all, they had said candies. When the children predicted that Nicky would think there were pencils in the box, she dragged Nicky in and asked him. Another group of children got very similar training about number problems—problems that had nothing to do with the children's understanding of the mind. At the end of the two weeks she asked the children a new question about false beliefs (about a set of soaps that looked like golf balls) The children who had received counter-evidence to their mistaken ideas about the candy box did much better on questions about the golf-ball soap than the children who had learned about numbers. But she also asked the children new questions about all sorts of other aspects of belief, questions such as where beliefs come from and how appearances and realities differ. The children who had gotten the counter-evidence not only did better on the questions about the trick objects, they also did better on lots of other questions about belief. By providing just the right kind of evidence at just the right time, we seem to have provoked a big, sweeping change, a sort of theoretical revolution, in the way these children thought about the mind.
We think that children learn about other people, and that they learn the same way scientists learn about the world. At first they may just ignore counter-evidence that contradicts their theory. In fact, three-year-olds will tell you that they said there were pencils in the box when they first saw it and will even maintain that Nicky said there were pencils in the box, when he actually said just the opposite. Gradually, though, as enough different kinds of contrary evidence accumulate, it's no longer possible to just ignore or reinterpret the facts. When the new theory finally replaces the old one, there are far-reaching implications. The new theory doesn't just let us deal with the contrary evidence; it also lets us understand many other phenomena in a new way. And the new theory lets us create a whole set of new predictions about what will happen in the future.