A Fetching Lexicon: Language clues come from dog’s vocabulary
On a European television broadcast 2 years ago, a border collie named Rico wowed viewers by correctly retrieving items from an array of children’s toys at the request of one of his German owners. For example, if instructed to “get the panda,” that’s what the black-and-white canine brought back.
Julia Fisher, a psychologist at the Max-Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and two of her colleagues watched Rico’s performance with keen interest. In ensuing experiments with the dog, they found that he recognizes the names of about 200 objects and learns names for new items as well as 3-year-old children have been reported to do.
“Our results support the view that rapid word learning by toddlers is mediated by simple cognitive building blocks that are present in another species,” Fisher says.
The dog’s word-learning skill is as good as chimpanzees’ and parrots’, the researchers conclude in the June 11 Science.
Initial trials indicated that Rico treats certain spoken words as names for specific items rather than using nonverbal cues, such as a speaker’s shrugs or gaze direction, to determine a word’s meaning. The scientists randomly assigned to 20 sets the 200 items Rico’s owners claim that the dog knows. While one of his owners waited with Rico in another room, an experimenter arranged the 10 items of one set in an adjoining room. He then told the owner to instruct the dog with a single verbal command to fetch a specific item.
Forced to search where he couldn’t see anyone, the dog in four tests retrieved 37 of 40 objects correctly.
An experimenter then placed a toy that Rico had never seen before with seven familiar ones in the adjacent room. Rico’s owner instructed him to fetch the item, using a name the dog hadn’t previously heard. In 7 of 10 trials, Rico returned with the new item. The researchers propose that the dog matched the unfamiliar word to a novel object through a process of elimination.
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One month later, Rico correctly retrieved three items during six tests, each test using one of these new words. That’s a good score, given that it was only the second time the dog had heard each word, Fisher says.
Rico’s interpretive skill partly stems from the breeding of border collies for mental agility. Also, 9-year-old Rico has been trained by his owners to retrieve toys by their names since he was 9 months old.
Still, it’s not yet clear whether Rico realizes that words refer to categories of objects, as even 1-year-old children do, remarks Yale University psychologist Paul Bloom in a comment published with the new report.