Danny Deraney tweets this:
But is the dog “practicing faces”? Or is it just trying to get some sort of reaction out of … another dog?
The thread that follows includes the claim that only three species besides us know that a reflection of me in a mirror is a reflection of me in a mirror: dolphins, great apes, and elephants.
But in my opinion, some dogs and some cats also pass this test. Not all dogs and all cats, because many dogs and many cats are thick as two planks. But many are not, and in my opinion are capable of working this out. As one tweeter says: “Some dogs” do have the sense of self that a mirror might reveal, if they get it. Some dogs do work out that “that’s me there”. Ditto some cats.
By the way, the reason cats and dogs vary so much in intelligence is that they have been bread by humans who were selecting for other qualities besides intelligence, like: docility, obedience, sociability, and cuteness. On the whole, intelligence was not being selected for (especially not with cats), and consequently it varies hugely. In my opinion.