I think what surprised me about this is that Gromit is a very stylized dog. He doesn't have a lot of the features of a real dog. He doesn't bark. He reads the newspaper and walks on two legs (sometimes) and expresses himself mostly through his eyebrows. Yet Kirby unmistakeably recognized this clay figure as a dog. He didn't bark at the clay people. He didn't bark at any of the other animals. Just Gromit.
This got me to thinking about dog facial recognition. What makes a dog a dog to another dog? I always figured it was a combination of how they look and how they smell and sound. Most dogs we see on television are barking or panting or otherwise making noise. In this case the only clues were the face and ear shape, big humanlike eyes and a round black nose.
Gromit may act like a person, but, according to Kirby, he is most definitely a dog.