In another experiment, researchers recorded “alone barks” of dogs when they were alone, and “stranger barks” when a stranger was approaching. When researchers played three “alone barks” to different dogs, these dogs showed less attention to each bark. But when they played the fourth bark, the “stranger bark,” the dogs quickly jumped to attention. They did the same thing when the barks were reversed, showing that dogs could clearly distinguish between the two types of barks. Using a similar test, the dogs also distinguished between the barks of different dogs.
How well do people understand what dogs are saying? Researchers played a collection of barks to a group of people. Regardless of whether they owned a dog or not, most people could tell from a bark whether a dog was alone or being approached by a stranger, playing or being aggressive. Unlike dogs, people were not very skilled at discriminating between different dogs. The only time people could tell between different dogs was when they heard the “stranger bark.” This is the exact moment a dog owner would be most likely to want to understand the meaning of a dog bark, since strangers can mean trouble.
These initial studies show that growls and barks do carry meaning that other dogs and, in some cases, people can recognize. This complexity comes as a surprise. Of course, our dogs have known all along—just ask Chocolate and Cina. Still, we know very little about the vocal behavior of dogs.
Brian Hare is an associate professor of evolutionary anthropology at Duke University and the Center for Cognitive Neuroscience, where he founded the Duke Canine Cognition Center. Vanessa Woods is a research scientist at the center as well as an award-winning journalist and the author of Bonobo Handshake: A Memoir of Love and Adventure in the Congo (Gotham, 2010). Hare and Woods are married and live in North Carolina.