IN THE age-old war between cats and dogs, canines might just have struck the killer blow. A border collie called Chaser has been taught the names of 1022 items – more than any other animal. She can also categorise them according to function and shape, something children learn to do around the age of 3.

Chaser follows in the footsteps of Rico, who trained at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Rico had a “vocabulary” of 200 words and could identify new objects in a group of familiar objects by a process of elimination, according to a study published in 2004.

To find out whether there was a limit to the number of words a border collie could learn, psychologists Alliston Reid and John Pilley of Wofford College in Spartanburg, South Carolina, started an intensive training programme with Chaser.

Over three years, they taught the collie the names of 1022 toys by introducing them to her one by one, getting her to fetch the toy and then repeating the name to reinforce the association.


The team regularly tested Chaser on her entire vocabulary. Groups of 20 toys were chosen at random and put in a separate room from where Chaser had to retrieve them by name. The toys were in another room so the trainer would not unintentionally give Chaser cues about which toy to choose. According to Reid, the dog completed 838 of these tests over 3 years and never got less than 18 out of 20 right (Behavioural Processes, DOI: 10.1016/j.beproc.2010.11.007).

Chaser was also taught to categorise the named objects, complete tasks such as touching the toy with her nose or paw, and like Rico, she could infer the name of a new object from a set of familiar objects.

“The experimenters did a lot of controls to exclude alternative explanations, although from my experience the results are simply too good,” says Ádám Miklósi, founder of the Family Dog Project at Eötvös Loránd University in Budapest, Hungary. Other dogs perform similar tasks, he says, but they usually make more mistakes. He thinks Chaser’s intensive training explains the difference.

“This study shows that this dog has good skills for comprehension but the production side of communication is missing,” says Miklósi. Others animals have demonstrated impressive feats of learning in which they also vocalise the words they learn, such as Alex, the grey parrot, who could make sentences out of about 100 words.