'Chaser' book cover

Chaser: Unlocking the Genius of the Dog Who Knows a Thousand Words is about psychologist John Pilley, his Border Collie, Chaser, and a retirement project that broke new ground in the field of animal cognition. It's also an inspiring story about a man whose curiosity has kept him going well into his 70s.

It's Not a Trick

Teaching a dog a thousand words is obviously a lot of work, but what was maybe even harder was to convince fellow scientists that a dog can understand even one. And if your dog always comes running when you say "cookie," you may wonder, what's wrong with those scientists? Partly it's that there's a long history to fight.

"A common belief that started with Descartes centuries back is that lower animals cannot reason. They're just machines with blood," Pilley says. "That view continues to persist among linguistic scholars who are not aware of the research that's going on with animal psychologists."

But to be fair, scientists are cautious because people have been fooled before. The animal in one famous case has been immortalized in the scientific lexicon: Researchers talk about needing to avoid the "Clever Hans" effect.

Clever Hans was an early 20th-century horse whose trainer believed he could do arithmetic — until a cleverer observer proved that Hans was actually just reading the trainer's body language. The horse, who answered by tapping his foot, had learned to stop when the trainer unconsciously relaxed at the correct number of taps.

Chaser and John Pilley

Animals are good at picking up on those kinds of clues, so experiments have to carefully exclude them: Does your dog always get a cookie when you're standing in front of that particular cabinet? When you use a certain tone of voice?

So Pilley had to prove, for instance, that Chaser could fetch a toy that he couldn't see, so he couldn't accidentally clue her in by looking at the right object. It also wasn't enough that she understood a word when he spoke — she had to respond correctly to other people, something many of our dogs do not do with words and commands that they seem to know.

Higher Concepts

What made it even harder to convince the scientific community was the kinds of words Pilley taught her. Chaser knows not just proper nouns — say, "bear" for a particular toy — but common nouns as well, like "toy."

"Learning a proper noun is really nothing more than a label for the object," Pilley says. "But when you learn a common noun, you've learned a concept."

Toys like a ball, a rope, a Frisbee and a stuffed bear don't all have a physical quality in common — what defines them is the abstract idea that they're something you play with. Scientists once thought that concepts like this were unique to humans. And, in fact, even human children don't realize at first … that one word like "toy" can refer to many different objects. But Pilley's work with Chaser has shown that a dog can understand this.


More Than Vocabulary Lists

How Chaser learns also goes far beyond memorizing a list. She can infer that a new word is the name of a new object without being explicitly taught.

"We put familiar objects out on the floor for which she had learned a proper noun name," Pilley says. "Then we took a novel object that she'd never seen before, and she'd never heard the name of it."

To make sure Chaser didn't go for the new object just because new things are interesting, first she was asked to fetch a couple of familiar toys. Then he told her to get "Darwin," a word she'd never heard before — and that's exactly what she did.

"She made an inference like a child would," Pilley says, the inferred logic being that if Pilley had wanted a familiar object, he would've used the familiar object's name. Since he used a name Chaser did not know, and there was just one object there without a familiar name, she made the connection that the new word corresponded to the unknown object.

Perhaps most impressive, Chaser has learned some elements of sentence structure, as shown in experiments where she is asked to move her toys around. She can tell the difference when she's asked to take a Frisbee to a ball or the opposite, take a ball to a Frisbee, without being explicitly taught each sentence.

Try This at Home?

If you're still insisting that your dog knows words, too, you may be right. Although the book's title refers to Chaser's "genius," Pilley says he believes that other dogs can learn words with proper training.

If you're inspired to try, one important lesson is that while Pilley is doing a lot of heavy scientific thinking behind the scenes, for Chaser, it's just a huge amount of fun. To motivate a dog to learn, you have to make it matter to her.

"Dog owners need to be aware that words don't have any meaning for them unless [the thing linked to the word] is related to their activities," he says. "Before the dog is even going to listen to words, that object has to take on value for that dog."

So Pilley didn't try to teach Chaser the words for, say, book or telephone. She's incredibly toy motivated, and he made use of that. "That ball has value for Chaser and other dogs because they can play with it," he says. "Then once that object has value, the name of the object can take on value, and then the dog will listen to the word because they get to play with that object."

A Special Team

Even if what Chaser has accomplished is possible for other dogs as well, someone had to figure out how to do it first, and it probably had to be a pair like Pilley and Chaser. Pilley thinks that a consummate herding dog like the Border Collie is already primed for this kind of task.

"In our book we talk a lot about the Border Collies that work with farmers — how they solve difficult situations in working with the sheep," he says. "The Border Collie has been bred for centuries to listen to the farmer and keep their eyes on the sheep. Our hypothesis is that this breed has a special propensity to listen to the words of the farmer."

And Pilley clearly has some special propensities as well.

"If he were a dog, he would definitely be a Border Collie. He has to do; he can't sit," says Pilley's daughter, Deb Pilley Bianchi. "Growing up with my father, everything was an adventure. The reason he didn't accomplish these things earlier is partly that he was busy living his life with a richness that most people don't ever experience."

And it seems like that's still true. When asked why he started this project at age 76 when he could have been sitting on the beach, Pilley says, "I'm not sure I really even know." But one thing he does know is that it has a lot to do with Chaser. "Her enthusiasm for life and for play is contagious," he says, "and life is about doing things."