I’ve read that you should teach children that dogs don’t smile and that if they see a dog’s teeth, then they should respectfully leave the dog alone. This is sound advice to help reduce bites of children who don’t have the maturity and discernment to read nuanced canine body language.
However, it’s not actually true. Dogs do smile, and what’s more, it’s apparently the only facial expression that they reserve for human beings; a dog will never smile at another dog. So it is probably mimicry that has survived because it was rewarded. I know that I melt every time Spencer cocks his head at me and smiles in attempt to charm another treat or piece of kibble out of me.
This expression seems to be a lot harder for Spencer to manage consciously than many of his other tricks involving body movements. Maybe he is less aware of his facial muscles than he is his paws and body, but it’s a relatively hit-or-miss affair whether he will produce a smile on command. In any case, there’s no way he’ll produce one unless he’s very relaxed/happy and it helps greatly if he’s asking for more food.
If you think the still shot is cute. Watch him smile on video.