For one amazing dog, the words "sit," "fetch," and "roll over" aren't the limits of her language -- they're only the beginning. Six-year-old female border collie Chaser has been trained by her owner to understand more than 1,000 words, along with simple sentences.
Chaser's owner, John Pilley, has spent years training and testing the limits of her intelligence. The 82-year-old psychology professor used children's toys and other objects to teach Chaser nouns, and she's still learning new things.
Watch "Nova scienceNow" on PBS tonight for more on Chaser's amazing abilities
Over the course of three years, Pilley spent four to five hours a day teaching Chaser about new objects and their names. Pilley jokes that he almost had to go to bed at 8 p.m. just to keep up with the Chaser's never-ending energy and attention to the training.
"She was born to live in the Scottish mountains and herd sheep," said Pilley, who is retired from a teaching career at Wofford College in Spartanburg, S.C.
Eventually, they amassed a collection of 1,022 objects: 800 stuffed animals, 116 balls, 26 "Frisbees" and other assorted items, each given a distinct name. There's even one stuffed cube, named "ABC."
PBS host Neil deGrasse Tyson visited Pilley and Chaser recently for a Nova documentary and quizzed the dog's remarkable memory with a random sampling of toys. The toys were placed in another room, and as Tyson called out the items by name, Chaser would go and retrieve them.
Tyson also brought along a new toy -- a doll named "Darwin" -- which Chaser had never seen before. When he asked her to find it in the other room, Chaser could locate the doll amid the other toys, inferring that the new object was connected with the new word.
"Whoa! " Tyson said to Chaser, tail wagging with "Darwin" in her mouth.
Chaser has also demonstrated the ability to understand verbs, including "find," "nose" and "paw," performing each of the actions on any of the 1000 objects.
Researchers suggest that Chaser's abilities represent far more than an impressive trick -- they could give insight into how human beings learn language. Other dogs have shown a similar knack for acquiring words.
"The flexibility we see in dogs seems to be very similar to what you see in young children at a very important age in their development," said animal researcher Brian Hare at the Duke Institute for Brain Sciences.
Hare studies primates, including chimps and bonobos, which have shown the ability to learn sign language and solve sophisticated problems. But their learning is slow compared with Chaser's ability to quickly learn and recall new words.
Hare believes that primates lag behind dogs in one key area -- social intelligence. Chimps often don't pay attention to their trainers, but dogs are always sensitive to their human masters.
"When I see my dog, my dog wants me to be around. He wants me to be his social partner. He actually needs me, whereas a bonobo and a chimpanzee -- they don't need me," Hare said.
Some researchers hypothesize that over tens of thousands of years of domestication, dogs have developed a humanlike social learning ability. To test this theory, he and other primate researchers are now setting up dog research labs.
"Over the centuries, there was inbred this special attention to words," Pilley said.
Pilley himself has just published a paper that documents his training methods and Chaser's ability to comprehend complex nouns.
Canine research may just be getting started, but Pilley and others hope that more dogs may now teach people a trick or two about how human learning works.