From an evolutionary perspective, dogs are incredibly successful. Their numbers speak to that. Given that dogs share their environmental niche with humans, their success must be a result of learning how to read us. Not just reading human behavior but, I believe, learning to read our intentions, which means that they have a theory of mind for humans. And that is exactly what we found in the Dog Project. So even though Callie and McKenzie were rarified representatives of the world dog population, what we found in their brains showed the defining characteristic of dogs: social learning. Their brains showed that they cared about human intentions.
Proof of social cognition means that dogs aren’t just Pavlovian learning machines. It means that dogs are sentient beings, and this has startling consequences for the dog-human relationship.
Most of the dogs in the world are village dogs. They are not anyone’s pets, although they might look that way at first glance because they often gather near humans. People know who the dogs are, but they might not have names. Village dogs insinuate themselves into the fabric of human societies. They feed on scraps, sometimes garbage, and sometimes food that is deliberately left by humans for them to eat. In some parts of the world, people let them hang around just so that they can eat them later.
If Callie had lived anywhere else in the world, she would have been a village dog. She had that rangy appearance—not too big, not too small—and the eyes of an opportunist. For the first year that she lived in our house, I was convinced that she would run away at the first opportunity of something better. But after the Dog Project, I no longer thought that. The project had changed both her brain and mine.
Indeed, if there is one thing dog ethologists can agree on (and it might indeed be only one thing), dogs are masters of change. If nothing else, dogs’ defining characteristic is their adaptability. Apart from vermin, dogs are the only mammalian species that is found everywhere humans are, and humans have occupied every habitable niche on the planet. As the ethologists Raymond and Lorna Coppinger observed, “The rapidity with which the dog has changed form, and the seemingly endless varieties of its form, challenge the theory of Darwinian evolution, that adaptation must be a slow process.” The Coppingers were referring primarily to dogs’ changing physical form, but the same can be said for dogs’ behavior.
When scientists speak of behavioral change, they are really talking about learning. And, as far as we know, there are only two mechanisms of learning that animals employ: associative learning and social learning. For a century, Pavlovian behaviorists have argued for the predominance of associative learning. Animals, dogs included, are great at learning associations between neutral events and things that they like, such as food, or things that they don’t like, such as pain. But associative learning cannot explain all of animal behavior. For one, it is inefficient. For an animal to learn associations, it has to actually experience the events. This is a trial-and-error process. By this learning mechanism, a dog would actually have to touch its paw to a hot stove to learn that that is something to be avoided.
Social learning is far more efficient. Many animal species employ social learning. Songbirds, for example, learn their species-specific calls from each other. But besides humans, dogs may be the best of all. By watching other dogs, Fido can learn a great deal. He doesn’t have to burn his paw to learn that the stove is dangerous if he sees another dog (or human) do the same. And, of course, puppies learn from each other and their mother, copying behaviors like pulling toys.
I have often wondered how dogs got so good at social learning. While many animals learn from members of their own species, dogs are one of the few that can learn from other species. Herding dogs, for example, learn by observing sheep and cattle. And all dogs learn by observing humans and other members of their households, just like Callie learned how to open doors. Village dogs, even though they are not attached to specific humans, exemplify this ability for social learning. There is no other way they could keep up with the ever-changing form of human society.
In the hot dog experiment, we found that the meaning of the hand signals had transferred to the caudate—a brain region known to be associated with positive expectations. While a cool scientific finding, it was not really unexpected given what we had known about Pavlovian learning. What was more revealing, and what we never commented on in our academic papers, was all the other stuff going on in Callie’s and McKenzie’s brains. The motor cortex activity. The inferior temporal lobe. Those were the regions that pointed toward a theory of mind, and they were the same regions that popped up in the smell experiment associated with familiar humans.
These cortical regions showed that the dogs might be constructing mental models of our actions. The inferior temporal lobe suggested that they were recalling memories, perhaps what one hand pointing up meant, or the identity of the person associated with a sweat sample. These are the types of mental processes that any sentient being would use on a daily basis. Humans use memories and ascribe meaning to people and actions all the time. Apparently, so do dogs.
Even though we found evidence for canine theory of mind in our experiments, Callie and McKenzie were not exactly the same in this regard. They showed differences in how their brains reacted to the hand signals and to the smells. With only two subjects, it is difficult to draw sweeping conclusions, but I will take scientific license to speculate.
In the hot dog experiment, McKenzie had stronger caudate activation to the “hot dog” hand signal. Strangely, Callie was the food lover, while McKenzie much preferred toys as rewards during training. Because of her great love of hot dogs, I had expected Callie to show the stronger caudate activation. But she didn’t. One possibility is that because Melissa and McKenzie had competed in agility competitions, McKenzie was more attuned to hand signals. I had not taught Callie a hand signal before the Dog Project, which might have put her at a relative disadvantage. Another possibility, which I think is very likely, is a genetic basis.
Even though we thought she was a feist, Callie was more like an adopted village dog. A mutt. McKenzie, on the other hand, was meticulously bred to be a herding dog. Border collies are known for their stares, what the Coppingers refer to as the eye-stalk. Border collies don’t just see with their eyes; they use them to control other species. There may have been much more going on in McKenzie’s brain as she not only interpreted Melissa’s signals but also returned them with her eyes. While I had noticed a flicker of that in Callie when her eyes dilated in anticipation, it was nothing like being stared down by a border collie.
In the smell experiment, though, the pattern reversed. Callie had the stronger response to the familiar human smell. Maybe that was because Callie slept with Kat and me in our bed, while McKenzie slept in her crate. Or maybe the bond between Callie and Kat was stronger than that between McKenzie and Melissa’s husband. Could it be that our dogs tell us more about our human relationships than we tell ourselves? The term therapy dog would take on a new meaning.