Support Provided ByLearn More
EvolutionEvolution

Chaser, the language-learning dog with a 1,000-word vocabulary, has died

The border collie achieved international fame for her remarkable grasp on vocabulary and sentence structure.

ByKatherine J. WuNOVA NextNOVA Next
chaserdarwin2 2.jpg

Chaser with a Charles Darwin plush. Chaser was able to pick Darwin out of a pile of toys despite having never seen the toy—or heard the word "Darwin"—before. Image Credit: Julia Cort, NOVA

The world has lost a very good—and very clever—girl.

Chaser, the border collie who garnered international attention for her impressive vocabulary of more than 1,000 words, died last week at her home in Spartanburg, South Carolina. She is survived by members of the Pilley family, her owners since 2004—and an enduring legacy of language learning many once thought impossible for canines.

During her 15 years of life, Chaser displayed a remarkable knack for nouns, learning to distinguish between all the members of a massive collection of well-worn toys. But her gift extended beyond one of rote memorization, says Pilley Bianchi, daughter of owner Sally Pilley. Chaser didn’t just pick up words and remember them. She mastered them conceptually, distinguishing verbs from adjectives, and categorizing objects she’d never seen—not unlike, Bianchi says, a human toddler learning to speak.

Support Provided ByLearn More

The late psychologist John Pilley, Chaser’s original owner and Bianchi’s father, first began training the pup in 2004. At the time, experts in the field were abuzz about another dog in Germany who’d been taught to tell apart 200 items. But Pilley, then 76, had a hunch Chaser might be capable of more. Over the course of the next three years, he patiently coached Chaser on a daily basis, showing her objects like squeaky toys, stuffed animals, and even pieces of clothing, while repeating their names over and over.

Some of the monikers were straightforward—a dolphin plush called “porpoise,” a duck dubbed “mallard”—while others, like a monkey referred to as “Uncle Fuzz,” were a little more whimsical. In total, Pilley showed Chaser 1,022 objects. And she remembered them all.

Robin Pilley Toy Pile.JPG

Chaser with her pile of 1,000-plus toys, each of which she knows by name. Image Credit: Courtesy of Robin Pilley

That was just the beginning, Bianchi says. As Pilley continued to push the limits of Chaser’s language learning abilities, the boundaries only seemed to expand. Chaser didn’t just retain the names of objects: She could sort them into categories, like balls or sticks, based on their common characteristics, even if she’d never encountered the items before.

The same logic applied to tasks of inference. Presented with a group of familiar objects with one foreign interloper, Chaser could nose out the new item, presumably through process of elimination. If she heard an unfamiliar word, she attached it to an unfamiliar thing—an advanced deduction for even a primate. (Watch Chaser do this with NOVA scienceNOW.)

She could also tell the difference between verbs (fetch, take, chase) and adjectives (long, short, big, small). Chaser even seemed to heed the rules of sentence structure—a hint that she had some grasp of grammar.

It became clear that Pilley had stumbled upon something very unexpected. For Chaser, words had meaning, Bianchi says. They weren’t just repertoires of sounds; they were concepts.

All the while, Chaser remained an eager and facile student. Like the rest of her border collie breed, she was an indefatigable worker for one simple reason: It was fun.

“It was actually very simple for Chaser,” Bianchi says. “She learned everything through play. [Learning vocabulary and grammar] sounds very complicated, but for Chaser it was very organic. Her joy of repetition was only exceeded by our exhaustion of it.”

Perhaps this isn’t surprising. For generations, border collies have been bred to maintain a certain professional intimacy with the shepherds they originally served. “Watch a collie work with a sheepherder, and you will come away amazed how small a gesture the person can do to communicate with his dog,” Alexandra Horowitz, a dog behavior expert at Barnard College, told Nicholas Wade at The New York Times in 2011.

But Chaser’s particular talents were enough to garner some attention, and Pilley ended up publishing two peer-reviewed papers on her accomplishments. The pair continued their partnership up until Pilley’s death in June 2018—an event that left the then 14-year-old collie in the hands of Pilley’s wife, Sally, and daughter, Robin, in their home in South Carolina.

Earlier this month, Chaser began to deteriorate from what veterinarians confirmed to be natural causes, Bianchi says. She died on Tuesday, July 23, at the age of 15—a little beyond the typical lifespan of her breed. Following Chaser’s burial in the backyard of the family home, the Pilleys sprinkled some of John’s ashes on her grave.

Mark Olencki (2).jpg

Chaser with John Pilley. Image Credit: Mark Olencki, Wofford College

Chaser was special, but not necessarily unique, Bianchi says, and there’s no reason other dogs can’t preserve and build upon the legacy she’s left. “My father’s goal was to shift the paradigm,” she says. “Dogs are smarter than we give them credit for. He believed there will be a world of Chasers. Humans aren’t at the top of the intellectual ladder.”

For the Pilleys, though, Chaser’s memory is cherished for far more than her mental acumen. She was a study subject, but also a loyal companion and beloved family member, with an infectious enthusiasm that charmed researchers and journalists alike. And not all her commands were for business: Chaser eventually learned that the word “hug” was a request for her to leap into the arms of the beseecher.

Despite her penchant for knowledge, Chaser wasn’t exactly an obedient dog, Bianchi says. “She was a character,” she recalls with a laugh, pointing to the collie’s sense of sass. If Chaser wasn’t a fan of someone—human or canine—she made it known. All you had to do, Bianchi explains, was say their name and see if it elicited a growl. “She knew the names of all the dogs and people [she went on walks with], and she had an attitude about each of them,” she says.

chaser red ball courtesy Pilley Bianchi.JPG

Chaser with a red ball. Image Credit: Courtesy of Pilley Bianchi

Chaser’s mischief also marks one of Bianchi’s fondest memories of the collie—a time when she bolted from Bianchi’s side during a visit to NBC Studios in February 2011. Winter storms had all but shuttered the city, Bianchi says, leaving poor Chaser cooped up in her apartment. The expanse of the studio was the first open space the collie had seen in days. After racing gleefully around the studio, she reappeared with a beach ball she’d filched from a storage room and began to bark and bounce the ball on her nose.

“That ball never touched the ground,” Bianchi says. “We’d never seen her do that.”

“My father really encouraged her to solve problems and just think for herself,” she says. “The studio hands were like, ‘Wow, that’s so awesome! How did you teach her to do that?’ And we just said, ‘We didn’t. She’s just doing it.’”

Receive emails about upcoming NOVA programs and related content, as well as featured reporting about current events through a science lens.