Q. How does one dog instantly recognize another as a dog, not some other animal?

A. Studies of dogs’ ability to discriminate their kind from other animals show that they can do so based on purely visual evidence, even in images.

This is even more remarkable in view of the fact that “domestic dogs, Canis familiaris, present the largest phenotypic diversity among domestic mammals,” in the words of one study, done in France and published in 2013 in the journal Animal Cognition.