Chaser the Border Collie: The Dog With a 1,022-Word Vocabulary
Plenty of dogs know “ball” and “sit.” Chaser knew the individual names of over a thousand distinct objects — and could tell the difference between a name and a category.
Chaser is the standard reference for Border Collie cognition — see the full list in our most intelligent dog breeds guide.
Nine years, five hours a day
Retired Wofford College psychology professor John W. Pilley trained Chaser for roughly nine years, up to five hours a day, five days a week. His method: show her an item, repeat its name up to 40 times, hide it, then ask her to retrieve it by name.
More than memorization
The breakthrough wasn’t just the word count. Chaser could distinguish between category words like “ball” or “Frisbee” and the individual proper names of over a thousand specific toys, and she could follow simple two-step sentence commands such as “take X to Y” — evidence that she understood something closer to sentence structure than rote association. The findings were published in the journal Behavioural Processes in 2011.
A legacy in canine science
Researchers called Chaser “the most scientifically important dog in over a century” for what her performance revealed about animal cognition. Pilley died in June 2018; Chaser died in July 2019 at age 15.
Chaser’s vocabulary record sits alongside Zeus, Purin, and Bobi among Guinness-caliber talents in our famous dogs guide.
Frequently asked questions
How many words did Chaser know?
Chaser learned the individual names of 1,022 objects, the largest tested vocabulary ever recorded in a non-human animal, documented in a 2011 study in the journal Behavioural Processes.
Who trained Chaser?
Retired Wofford College psychology professor John W. Pilley trained Chaser for roughly nine years, up to five hours a day, five days a week.
Is Chaser still alive?
No — Chaser died in July 2019 at age 15, about a year after her trainer, John Pilley, passed away in June 2018.
