Owners who insist their dogs can smile are correct in thinking that the
canine mouth can show emotions. Relaxed and open, it can be a sign of a
happy dog. A submissive grin is a canine version of our nervous smile.
Dogs pull their lips up, show their front teeth, and may crouch. This
harmless, nervous "grin" is easily confused with an aggressive snarl.
When in doubt, don't mess with the dog.
