What Napoleon did wasn’t quite that sophisticated. By dropping the ball in front of MacLean, he demonstrated that he knew where his owner’s attention was focused, which is not quite the same as knowing what MacLean was thinking. Had he released the ball behind MacLean, however, it would be a pretty safe bet that the dog had zero theory of mind. Chimpanzees pass a similar test. Place two chimps in a room with a plate of grapes, and the chimp lower on the social totem pole won’t grab one until the higher-ranking chimp looks away. The animals also clap their hands and make raspberry noises with their lips when they want to get the attention of a researcher who isn’t watching them.

In the next experiment, however, Napoleon does something chimps can’t do. MacLean stands near a wall with the dog on a slack leash, while a female graduate student sits on a chair in the center of the room. She sets two opaque red cups upside down on the floor, one on each side of her. Then, as Napoleon watches intently, a third graduate student enters the room. She places the dog’s tennis ball under one of the cups and pretends to place it under the other, obscuring her motions with a small black board so the terrier isn’t sure which cup contains the ball. If this were a shell game, the dog would have a fifty-fifty shot of picking the right cup. But the seated graduate student gives him a hand, or, more precisely, a finger. She points to the cup on her right, and when MacLean lets go of the leash, Napoleon runs over to it and retrieves his ball. Over several trials, the dog always goes for the cup that is pointed out. Even when the seated student merely gazes at the correct cup, Napoleon gets the message.

This may seem like a simple test, and, indeed, even one-year-old children pass it. But our closest relatives, chimpanzees, fail miserably. They ignore the human helper, pick cups at random, and rarely score above chance. Brian Hare’s lab has become famous for spotting this difference. Napoleon has performed more than just a neat cognitive trick. He has displayed a more complex skill related to the development of theory of mind in children. He wasn’t just clued into the pointing student’s attention; he had shown behavior consistent with understanding her intention. He showed that he realized that the student wanted to show him something, that she had a desire.