It's unclear why the researchers believe that when a dog doesn't learn the names of a bunch of toys it means that they can't.
There are lots of things people are able to learn today that they "couldn't" a few years ago (programming, math, reading). How are the researchers able to tell that the limitation lies with the dog and not with the trainer/household?
There are lots of things people are able to learn today that they "couldn't" a few years ago (programming, math, reading). How are the researchers able to tell that the limitation lies with the dog and not with the trainer/household?