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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.
John Pilley and Alliston Reid demonstrated their own border collie bitch, Chase, learned the names of 1022 objects, over three years, – no upper limit is apparent – they stopped training the dog after three years due to their time constraints, not because the dog could not learn more names.
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. The authors admitted that she remembered the names of each of her 1022 toys better than they could.
Their second experiment demonstrated that Chaser really understands that these are names, and not commands to fetch the object. In order to test this, the authors randomly combined names with commands to see if Chaser would produce the correct behaviour toward the correct object in each trial. The commands included ‘bring’ ‘paw’ (push it with your paw) and ‘nose’ (move it with your nose). Without special training, Chaser responded to each combination correctly, even on the first trial, demonstrating that Chaser understood that the commands and names had independent meanings.
Their third experiment demonstrated that the dog also understands names for categories of objects, and not just individual names. For instance, she learned that name “toy” referred to the 1022 objects she was allowed to play with, each with its own proper-noun name. By forming categories represented by common nouns, Chaser mapped one label onto many objects. Chaser also demonstrated that she could connect up to three labels onto the same object without error. For example, Chaser knew the individual names of all objects used in the research. Chaser also mapped the collective word “toy” onto these same objects. Her additional success with the two common nouns “ball” and “frisbee” demonstrates that she mapped a third label onto these objects. Her demonstrations of one-to-many and many-to-one noun/object mappings reveal flexibility in the referential nature of words in border collies.
Their fourth experiment demonstrated that Chaser could also learn names by exclusion – inferred the name of a new object by exclusion of familiar already-named objects. Retention of these names using this procedure was limited to short periods, however, just as usually observed with children.
The researchers claimed their research is important because ‘it demonstrates that dogs, like children, can develop extensive vocabularies and understand that certain words represent individual objects and other words represent categories of objects, independent in meaning of what one is asked to do with those objects.”
This work encourages research into how the evolutionary relationships between humans and dogs may have influenced the abilities of dogs to communicate with humans, and whether this influence is unique to dogs.