[mikimm]

This really has turned into a great thread full of important information. I agree that dogs respond to their world in species dependent ways. They have to be intelligent to navigate successfully in our world as well as their own. They communicate with us and each other. They learn and they also teach. If they didn't do these things, they wouldn't be such a thriving species and "mans' best friend."

When the dogs were faced with a choice between the new dog on the familiar landscape and a completely new landscape with no dog, they reliably selected the option with the dog. These results show that the dogs were able to form a concept i.e. 'dog', although the experiment cannot tell us whether they recognized the dog pictures as actual dogs.

I think this study is flawed, though. I don't think it shows dogs categorizing at all. Dogs readily recognize dogs and prefer to interact with dogs. I'd be more amazed if some of the dogs preferred to select landscapes over dogs in the pictures.