I guess we know it, although some cat caretakers might like to believe otherwise. Cats who have a constant smile are just made that way. It is an accident of anatomy.
That said, it does not mean that cats don’t smile inside, feel content or happy. But when we see a smiling cat it is an emotion that we see in the cat from the shape of his/her muzzle. Perhaps we want to see it.
However, we can tell by the overall appearance of a cat’s face and general demeanour when a cat is content or depressed or indeed anxious. It is there; the subtle changes in facial expression.
But I don’t believe cats smile like we do.
Some cat caretakers believe their cats are “clowns” constantly larking around having fun with a smile on their happy face. This is our interpretation of their behaviour. It is probably the human projecting her desire or emotions onto her cat.
But…perhaps I am being too unenlightened, too scientific. Perhaps cats do smile. What does your experience tell you?