Training
Chaser, an eight-week-old Border Collie, was bought from a breeder in 2004. She was trained in simple obedience and socialising four to five hours daily. In Chaser’s fifth month, the focus moved to word teaching. To encourage her, incentives and rewards such as petting, attention and providing opportunities to engage in enjoyable activities (for example tugging, ball chasing, toy shaking, Frisbee play, agility play, walks, search by exploration, outdoor tracking and stalking), were used and were more powerful than the traditional use of food.

The experiments
Four experiments investigated the ability of a Border Collie to acquire receptive language skills. In the first experiment, Mr Pilley wanted to know whether Rico’s acquisition of over 200 words represented an upper limit for Border Collies, or whether an intensive training programme with abundant rehearsal could teach a more extensive vocabulary. Experiment two tested her ability to understand the meaning of nouns and commands. Experiment three explored the degree to which Chaser could learn several common nouns (words that represent categories), and in experiment four, her ability to learn words by exclusion were tested.

Experiment one
Chaser was trained daily for four to five hours over a three-year period to identify and fetch 1,038 objects. These were mostly toys for children or dogs obtained from second-hand stores, consisting of over 800 cloth animals, 116 balls, 26 Frisbees and over 100 plastic items. Objects were given a proper name and it was written down on the object with a permanent marker to ensure that all trainers used the correct name consistently in all training sessions.
Chaser was taught one or two proper-noun names per day. The names of the objects were repeated 20 to 40 times each session. Daily training procedures, the duration of the sessions and the amount of rehearsal were adjusted to adapt to Chaser’s ability to learn and retain new words. From five months old, she was given monthly tests of all the proper nouns that she had learned. She was able to respond correctly to more than 95% of the proper-noun objects she had learned.
Chaser accumulated and maintained this knowledge of nouns over a lengthy 32-month period. After three years of training, her accuracy was shown at a public demonstration in a college auditorium, were she got an impressive 92%! Training was stopped after three years because it became impossible for her trainers to invest the four to five hours per day.

Experiment two
To demonstrate that command-noun combinations were two independent units of meaning, Chaser was asked to produce appropriate behaviours when three different commands (take – to pick up the object with her mouth; paw – to touch the object with her front paw; and nose – to touch the object with her nose) were randomly combined with three different objects (a cloth named lips which resembled human lips; a cloth cube with the letters A, B and C written on its sides; and lamb, a stuffed toy resembling a lamb).
Chaser was 100% accurate across 14 trials, producing the correct behaviour toward the correct object in each trial. With this accuracy, Chaser demonstrated that she ascribed independent meanings to commands and names and that she could combine the two meanings accurately without explicit training.

Experiment three
This study assessed Chaser’s ability to learn three common nouns (toy, ball and Frisbee) that represent different categories of objects. She was allowed to play with all of the toys, but not with the available non-toys in the house that had similar appearances.Each trial began with Chaser standing beside the trainer in one room. She was asked eight times to retrieve an exemplar from the bedroom (for example “fetch a ball” or “fetch another ball”). She would enter the bedroom, select the object, return to the living room and place the object in a Tupperware tub. When Chaser was asked to retrieve a toy eight times in succession out of the 16 objects available, she correctly selected a toy without error in every trial.
This experiment showed that Chaser was successful in learning three common nouns – words that represent categories. She also successfully learned the more abstract concept of ‘toy’, which seemed to be based on function rather than shared physical characteristics.

Experiment four
This procedure involved a choice trial in which the dog was provided a novel name and expected to choose a novel object located among a group of familiar objects that already had associated names. Chaser retrieved each of the eight novel items in succession without error, ignoring the two familiar items. It is possible that a dog could correctly select a novel object and retain this name-object knowledge over time, comparable to the performance of three-year-old toddlers.

Conclusion
These four experiments done with Chaser provide compelling evidence that Chaser understood that objects have names. She probably learned more proper-noun names (1,022) than any other dog. She demonstrated the one-to-many name-object mappings required for common nouns to represent categories. She also understood that an object may have more than one name. By successfully responding to random combinations of names and commands, she demonstrated her understanding that names refer to objects, independent of the behaviours directed toward those objects. Thus, she understood the difference in meaning between names and commands and treated their combinations the same way humans do. Combined, these experiments provide clear evidence that Chaser acquired referential understanding of nouns, an ability normally attributed to children.

With special thanks to Mr. John W. Pilley

Text: Yolanda Wessels
Photography: Courtesy of Mr John W Pilley

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