SPARTANBURG, S.C. - The experiment began with a racquetball that has now been replaced many times.
"Chaser! This is Blue," said John Pilley, a retired Wofford College psychology professor.
"Blue," Pilley repeated, and rolled the ball to his 2-month-old border collie.
He said the name again as Chaser took the ball in her mouth and held it just out of reach in a coy game of keep-away. Tail wagging, paws clattering, she chased Blue across the room in what became the first steps in her training to learn human language.
Blue led to Bamboozle, a stuffed orange horse, Choo Choo, a squeaky rubber train, Cinderella, Dora, Drumstick, Ears and Elmo. The house filled up with toys - 800 animals, 116 balls and 26 Frisbees - kept in huge plastic bins on the back porch. Each had a different name written in marker; Pilley could no longer remember them all.
Chaser is now world famous as the dog who knows more than 1,000 words, the largest known vocabulary of any animal except humans. Besides proper nouns, she knows verbs, adverbs and prepositions. She's learned that common nouns can identify different things. Ball could mean any round or bouncy object, Frisbee any spinning disk or ring. And she can make inferences. If asked to fetch a new toy with a word she's never heard, she'll pick the toy out from a pile of familiar ones.
As her language learning grew, so did the experiment. Pilley has recently started to teach Chaser commands with three elements of grammar, going from the basic "take ball" to "take ball to Frisbee." This is what excites Pilley most as a scientist - that Chaser understands the concept that words play off of one another and that each word in a sentence can have a different meaning.
"We want to stretch it out so we have four, five elements of grammar. They've done that with dolphins and chimps, but no one's done it with dogs," he said.
There seems to be no end to Chaser's abilities and her fame. Since Pilley's findings were first published in 2010, scientists have begun to follow his work as he explores the extent of what dogs are capable of. His approach has led to a new understanding of canine intelligence, one that makes us wonder just how sophisticated a dog's mind can be.
Bred for intelligence
Long before Pilley got Chaser, he was intrigued by border collies.
As a breed, they seemed to have the instinctive ability to follow complex commands while herding livestock but also move them across great distances without supervision.
"You're not breeding them for their looks. You're breeding them for what's between their ears," said Wayne West, who's bred border collies since the 1960s.
Border collies are herders, bred hundreds of years ago to work with sheep, Pilley said. If a farmer's dog didn't listen to the farmer, the farmer didn't breed the dog. Through selective breeding, border collies gradually began to pay more attention to the words themselves.
Though they were quick to learn new behaviors, Pilley's attempts to teach dogs to understand words never got far. All of his research seemed to indicate that dogs didn't even know their own names.
"I wanted to do something other than teach, so finally, at age 67, I retired, but I couldn't find anything that I enjoyed more," he said.
Pilley's wife, Sally, was the one who decided for him. It had been almost a decade since they lost Yasha, a border collie-German shepherd mix, to old age. The time seemed right to get another dog.
Chaser arrived one June day on West's farm as the Pilleys sat beneath an old oak tree.
Although Chaser went home with them primarily as a member of the family, Pilley says he had it in his head from the beginning to teach her words. There was no science or study to go on; he'd simply have to follow Chaser's lead to figure out what worked.
The power of play
One of Chaser's favorite games is playing fetch on the stairs that lead to the Pilleys' loft. She'll nose Blue over the top step, watching it bounce this way and that until someone catches it and throws the ball back up to her.
Play was a powerful tool in teaching Chaser to learn words.
"Before she will listen to the words, they have to have value," Pilley said. "When we're playing with her - catch, find - she's having fun, and so that object takes on value ... and she's also having a relationship with the human."
Chaser had been with Pilley only a few weeks when the journal Science published an article about a border collie in Germany that knew more than 200 words. The Rico study, as it's called now, suggested that a language skill previously thought to be associated only with human children could also be present in another species.
Pilley was eight years into his retirement, but the article's timing with the arrival of Chaser turned him into a scientist again. He decided to set a goal; he would teach Chaser a thousand words and maybe write a paper himself.
In his new book, Chaser: Unlocking the Genius of the Dog Who Knows a Thousand Words, Pilley recalls those first years of training. He worked with Chaser for at least five hours a day over three years, slowly building her vocabulary. Pilley tapped into Chaser's border collie instinct to herd.
Each individually named toy was introduced as if it was part of a flock. "Come by Frisbee," Pilley might say, using the commands farmers would give collies on a farm. Fetching and finding objects all over the house made learning memorable for Chaser, but it took repetition. Each toy's name was said as many as 40 times during an exercise; each exercise was rehearsed 20 times over a day.
Chaser was then re-tested once a month to see what she could remember.
Her success rate never changed; she was right more than 90% of the time.
Pilley took Chaser down to West's farm for a demonstration. West had known that border collies could do extraordinary things. On their own, his dogs could figure out how to move sheep to the farm from half a mile away after learning a dozen basic commands, but Chaser went "far beyond what I realized a dog could have learned," West said.
The world seemed to agree. Pilley's research was published Dec. 8, 2010, and within a week, the news had spread to 46 countries.
Britain's Daily Mail headlined Chaser as the world's brainiest dog. On The Today Show, she was the canine Einstein.
Animal intelligence experts paid attention, too. Brian Hare, an evolutionary anthropologist at Duke University and author of The Genius of Dogs, called Chaser the most scientifically important dog in more than a century.
"There are lots of animals that have been trained to understand hundreds of words ... but what's interesting is how she learned them and the fact that she learned them through inferential reasoning," Hare said.
Pilley's work, along with that of others, has resulted in an explosion in the field of dog cognition. Hare founded Dognition earlier this year as a Web app for people to test their dog's intelligence and record the results. With enough samples, researchers will be able to better understand canine abilities.
"Nobody expected that of all the species out there, it would be dogs that have shown the ability to learn labels for objects like we do," Hare said.
For now, Chaser's training has been put on hold with Pilley's book release, but he doesn't plan to stop their journey of canine discovery.
Pilley often says that Chaser has the intelligence of a human toddler and the intense focus of a border collie. That's a powerful combination, but he believes all dogs have the ability to learn like Chaser with the right mix of praise, play and, of course, patience.
"One reason some of our findings are so important is that we demonstrated - and we're not alone; there are other researchers demonstrating the same thing - that these dogs think. They reason. They make inferences," he said.
(Copyright 2013 by USA Today. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed. )