Some clever dogs can pick up on the names of hundreds of toys just through natural interactions with their owners.
A team led by cognitive scientist Shany Dror from Eötvös Loránd University in Hungary found that so-called Gifted Word Learner dogs could learn the names of objects purely by eavesdropping on their owners' conversations – and even learn the name of a toy when it's out of sight.
This is akin to a process that human children as young as 18 months use to pick up language from adults by overhearing their speech and studying it closely for meaning, even when they aren't being directly addressed.
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Gifted Word Learner dogs aren't your average pooch. One such dog, a border collie named Chaser, could retrieve 1,022 toys accurately just based on their name, earning her the title of the "smartest dog in the world."
Gifted dogs like Chaser are rare, but their abilities offer a fascinating insight into canine psychology.
"To test this, we asked the owners of ten gifted dogs to let their dog passively observe as they talk to another person about a new toy," the researchers explain in a video abstract. "We then asked the owners to repeat this process with another new toy."
Part of their first experiment was based on previous studies used to test young children's ability to pick up vocabulary from overheard speech.
After watching their owners discuss each toy for two minutes daily across four days, the dogs were tested on their ability to correctly retrieve each new toy from a pile of nine other beloved, familiar options, based only on the toy name they'd overheard their owner using.
Seven of the ten dogs successfully retrieved their new toys at a rate that couldn't be accounted for by random chance, and were just as accurate as they had been when their owners directly addressed them to teach them the name of a new toy.
Where that experiment relied on a visual connection between the object and a spoken word, another test pushed things further by testing whether dogs can learn the name of an object that is concealed from view, something we know human children are capable of.
Dror and team asked each gifted dog's owner to put a new, unlabelled toy in a bucket while their dog was watching. After allowing the dog to remove the toy, the owner returned the object to the bucket once more.
Raising the bucket beyond the dog's view, the owner asked their dog if they wanted the toy, referring to it by a name while looking at the bucket.
Five of the eight participating dogs were able to correctly identify the toy by name from a pile of other toys at a rate above chance. When tested again after two weeks, the dogs performed equally well, suggesting their learning had 'stuck', at least in the short term.
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Typical family dogs (all of which were border collies like Chaser and Bryn) did not have the same success when put through these paces, which means breed is no guarantee your dog will be one of the gifted few.
"Our findings show that the socio-cognitive processes enabling word learning from overheard speech are not uniquely human," says Dror. "Under the right conditions, some dogs present behaviors strikingly similar to those of young children."
This research was published in Science.