WASHINGTON, Nov. 21, 2002 — When humans began domesticating wolves thousands of years ago, it was the beginning of a beautiful friendship. Many dog lovers say their pets seem to know what their masters are thinking. A study in the journal Science, published by the American Association for the Advancement of Science, suggests that might be at least partially right. Something about the process of domestication seems to have given dogs the ability to read certain human social behaviors — something wolves, and even chimpanzees, can’t do.
When Brian Hare, an anthropologist at Harvard University and the Max Planck Institute in Germany, was a student, he and his adviser were discussing whether chimpanzees can take another individual’s perspective.
“Oh, well, my dog does that!” Hare said.
When his adviser challenged him to prove it, a new line of research was born.
Hare has found that dogs are extremely good at finding hidden food in response to human cues, such as gazing or pointing. In his experiments, a researcher showed each dog a piece of food and two cups. Then, while a screen blocked the dog’s view, the researcher would put the food into one of the cups. After removing the screen, the researcher would gesture at the baited container.
Curiously, chimps did not do particularly well in these so-called “object choice tasks.”
“The idea of the object choice paradigm is that animals may be able to think about the thoughts of others, as humans do,” said Hare. “If you hide food and give them a social cue, they should understand that ‘hey, he’s looking at where the food’s hidden, he knows where it’s hidden because he’s hidden it; and he wants me to find it.’”
It’s possible that this type of understanding may be akin to humans’ ability to consider someone else’s point of view, according to Hare. Researchers call this type of perception “theory of mind,” Humans do this all the time, such as when we teach, or deceive others. The jury is still out on whether chimpanzees and other non-human primates possess theory of mind capabilities.
It will take more research to prove that dogs actually use theory of mind, but Hare says his experiments do indicate that dogs have some kind of mental ability to understand the intentions behind certain non-verbal signals from humans.
The orgins of prespective-taking
Hare and his colleagues came up with three possible explanations for why dogs might be capable of this particular sort of human mind-reading. For one, wolves may have evolved the ability to “put themselves in the shoes” of others well before humans came into the picture. Such a skill may have enabled wolves to predict, for example, which way their prey might run during a hunt.
If this scenario were correct, the researchers reasoned, dogs and wolves should perform equally well in the food-finding tests.
Alternatively, exposure to humans may be teaching individual dogs to read certain intentions communicated by their two-legged companions. In this case, puppies, especially those raised without much human contact, would likely not make the connection between a human gesture and the whereabouts of an edible treat.
The third possibility was that the domestication process itself had “hard-wired” dogs with this ability. Dogs that could understand their human masters in certain ways would thus have been more likely to pass along their genes than others.
Hare’s team repeated their experiments, this time comparing dogs with wolves from a wolf sanctuary in Ipswich, Mass. The wolves found the food less often than the dogs did — a strike against scenario No. 1.
The researchers tested their second hypothesis using several groups of puppies. Some had been reared by humans, while others were raised in kennels, with little human exposure. All the puppies performed relatively well, indicating that learning from humans had little to do with their ability to “read” the experimenters’ gestures.
Third time is a charm
In the end, the domestication hypothesis best explained dogs’ ability to read social cues from humans, the authors concluded — although nobody really knows for sure how or why humans and wolves forged the sort of bond that led to the existence of modern dogs.
Humans may have intentionally bred those dogs best able to “understand” certain human signals.
“It’s also possible that … dogs are better than other animals at this simply because they are domesticated,” Hare said. “When you get domesticated, you become calmer and potentially a little bit more attentive, so this ability may be a byproduct of the domestication process.”
Hare thinks that studying additional animals — a population of domesticated foxes is next on his list — should help shed light on which of these scenarios is more likely.
Interestingly, dog brains are only two-thirds the size of wolf brains, according to Hare.
“Most people think domesticated animals are dumb, and less able to solve problems,” he said.
Dog owners, of course, have always known otherwise.
Two additional studies in the same issue of Science also investigate the history of dog domestication. Using genetic evidence from dogs in Asia, Europe, Africa and Arctic America, one research team determined that dogs were first domesticated in East Asia, possibly as recently as 15,000 years ago.
A second research team compared DNA from dogs of the Old World and the New World, and found that several lineages of dogs seem to have accompanied humans into the New World. Thus, all dogs may have a common ancestor, the scientists propose.
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© 2013 American Association for the Advancement of Science