There's "caterpillar," "decoy," "tentacle," "bouncy" and, of course, "ball." If Chaser made a dictionary filled with all the words she knows, it would have many times the number that the average dog understands. The 6-year-old border collie boasts an astonishing vocabulary, and knows the names of 1,022 toys that she has been taught over the past three years.
Allison Reid and John Pilley, two psychologists at South Carolina's Wofford College, worked with Chaser in an intensive training program that included introducing new toy names one by one.
According to New Scientist, they tested her regularly to make sure she had retained the words — and she consistently did well. In total, the dog completed 838 of these tests over three years and never got fewer than 18 names right out of 20. She can also categorize them according to function and shape, something children learn to do around the age of 3.
Before Chaser, the dog who knew the most number of words was Rico, who trained at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. He had a "vocabulary" of 200.
"We wanted to see if there was a limit to the number of words a dog could understand, and if they could understand the name of an object rather than just respond to a command related to an object, such as fetch," Dr. Reid told the Daily Mail. "We're not saying this means dogs can learn language in the same way children do, but it does show they are capable of learning many more words than might have been thought."