Chaser, a Border Collie from South Carolina, knows the names of over 1,000 different objects. Does anyone find themselves looking at their tail-wagging friend and wondering, “Well, what do you know?”

When it comes to whether dogs can understand words, Chaser—the subject of not one, but two scientific publications—can attest that the answer is: Yes. Dogs can understand words! But Chaser can also attest that the answer could be highly dependent on what goes in, and how.

Chaser: Unlocking the Genius of the Dog Who Knows a Thousand Words came out in paperback last week. Renowned animal scientist Temple Grandin says it best, "After you read Chaser, you will realize that you may have underestimated the intelligence of your dog. Marvelous insights into a dog's mind."

Owners generally peg dogs as a wordy bunch. A 2001 study from the Family Dog Project in Budapest collected 430 different utterances that dog owners thought their dogs knew, 30 on average. The utterances fell into categories like invitation (i.e., “Come”), disallowance (“No! Stop it”), posture (“Sit”), object or person-related actions (“Find the sock,” “Go to mom”), permission (“You can go on the couch”), questions (“Where’s mom?” “You want to go for a walk?”), providing information (“Someone’s coming home!”), and unique (“Show me your tail!”). Owners overwhelmingly thought that their dogs responded appropriately to these utterances most of the time. Few utterances were thought to be followed only occasionally. The researchers made it clear that they were not trying to explore whether dogs actually understood words independent of context, at least not in that study. Instead, they were more interested in gathering a “collection of anthropomorphic anecdotes.”

But do ‘anthropomorphic anecdotes’ hold true? When researchers investigate whether dogs actually understand words independent from context, a different story appears.

Take Fellow, a performing German Shepherd from the 1920’s. When his skills were tested outside their typical context, Fellow only knew some of the words he was thought to know. For example, he performed well on commands that required no special orientation or position, such as “sit,” or “roll over,” but he performed less well on commands requiring specific orientation like, “go find my keys."

Patricia McConnell, Certified Applied Animal Behaviorist and adjunct professor at the University of Wisconsin-Madison, shared a more personal example with me in an interview for the article ‘Say What? What Our Words Mean to Dogs’ in The Bark magazine. McConnell initially thought her dog Willie knew the name of her husband, Jim, but she eventually realized that Willie thought something else was going on:

“To teach Willie, I would say, ‘Where’s Jim?’ and Jim would call Willie over. When Willie consistently went to Jim, I’d say it as Jim was driving up, and Willie would run to the window. One day, Jim was sitting on the couch, and I said, ‘Where’s Jim?’ and Willie ran to the window, all excited. This difference in definitions is more common than people realize — dogs don’t have the exact same concept of words that we do.” (Hecht, 2012)

For Willie, "Where’s Jim?" meant "Somebody is coming up the drive. Let's see who it is!"

Something different is going on for Chaser.

After years of working with John Pilley, an emeritus professor of psychology at Wofford College, Chaser proved that she knows a lot: she knows the distinct names of over 1,022 different objects (an Appendix in her book lists each of her toys from Acorn and Crybaby to Slug and Tie Face). Besides knowing the names of objects, she also knows that objects can fall into different categories—some objects are frisbees, others are toys and of course there are balls—and that some words relate to objects (such as ‘sock’) while others refer to actions (like ‘fetch’). She does not interpret ‘fetchsock' as one word, but instead, two distinct words, and she has been explicitly tested on the verbs ‘take,’ ‘paw’ and ‘nose.’

Last year I interviewed Pilley about teaching language to a dog. He stressed that a big part of Chaser’s learning lies in something both dogs and humans excel at:

P.L.A.Y. played a huge role in Chaser’s way with words. In the interview, which you can read here, Pilley walked me through their playful steps toward word learning. Of the handful of dogs whose word understanding have been tested, play seems a crucial part of their learning and training. For example, a 2012 study describes Bailey, a 12-year old female Yorkshire terrier, who learned the names of over 100 objects, also through play.

For more on the extraordinary bond between a word-happy canine and her devoted human, check out Chaser: Unlocking the Genius of the Dog Who Knows a Thousand Words.


References and recommended reading

Griebel U. (2012). Vocabulary Learning in a Yorkshire Terrier: Slow Mapping of Spoken Words, PLoS ONE, 7 (2) e30182. DOI:

Hecht, J. (2012). Say What? Do Dogs Understand Our Words? The Bark, Issue 72: Nov/Dec 2012

Hecht, J. (2013). How to Teach Language to Dogs. Dog Spies on Scientific American

Pilley, J., and Hinzmann, H. (2013). Chaser: Unlocking the Genius of the Dog Who Knows a Thousand Words. Houghton Mifflin Harcourt

Pongrácz, P., Miklósi, Á., Csányi, V. (2001). Owners' beliefs on the ability of their pet dogs to understand human verbal communication. A case of social understanding. Current Psychology of Cognition, 20: 87-107.

Warden C.J. (1928). The Sensory Capacities and Intelligence of Dogs, with a Report on the Ability of the Noted Dog "Fellow" to Respond to Verbal Stimuli, The Quarterly Review of Biology, 3 (1) 1. DOI: