Is my dog really "Smiling"?

Question:
 Hello, I'm new here and I am just posting a query i have regarding my Labrador Retriever. It is quite a long "problem" and you may not be able to help me out, but I'm really trying to find information out, possibly for my own safety? We brought Dexter home from a rescue centre about 12 months ago- he came from a family that were splitting up and couldn't take him where they were going- so it isn't like there is a serious abuse/neglect case history. He is a very friendly dog and he tolerates being pulled around, fussed and chased and troked by all people. He has NEVER shown aggression to anybody, in my presence anyway. We did notice that Dexter has a habit of "smiling"- curling his lips back to reveal his teeth slightly, with a sometimes-wrinkled nose. I am aware of the common aggressive signals dogs give off, and this was my first worry- but Dexter has never shown any other signs of aggression whilst doing this to people, such as growling or stancing himself ready to attack. He sometimes snorts slightly, but he also makes this noise when he has been working himself up during a petting session. His smiling doesn't seem aggressive in nature, but people have been scared by it when entering the house- he meets visitors at the door to greet them, smiling and waiting for a fuss. One of the first nights we had him, fireworks were going off and his smiling was quite frequent- which scared me, having no real background history of random behaviour; but since then he smiles on most occasions: when greeting people at the front door- especially those that he knows will give him a lot of attention, when we enter a room where he happens to be sleeping/laying he may smile, if you go over to him to sit near him when he is sitting in his chair he sometimes smiles and other times, he will just smile when you talk to him, fuss him or talk to somebody about him whilst glancing at him, he also smiles a lot during playtime in the garden and when receiving treats. As you can see, the scenarios are all very different, and his behaviour has left me very confused. I have researched into this, and the facial expressions he shows are similar- as i have said- to aggression but no other signs are there; i first thought it could be dominancy: he is showing teeth to let us know he is STAYING in his chair, he shows his teeth when we enter the house because he is showing us it is HIS territory. This could be quite understandable, if he wasnt so relaxed and laid back, with his tail wagging. I did read somewhere that when dogs are showing submission they may raise their lips to show some of the teeth and i thought that maybe this could be it- since he mainly smiles at our family or close friends that he knows. Since the rolling onto his back is also submissive- and he smiles whilst being tickled in this position- i thought that maybe this could be another way of him showing us he knows who is in charge. A rather embarrassing habit Dexter has is rubbing his rear end accross the carpet; i know this is generally due to irritated anal glands that need emptying, but i also read that it is a sign of submission. He does this quite often recently, and the first time he did it people found it amusing (until they realised what he was actually doing) and he emerged from his crouching position with a wide smile- as though he knew he was entertaining people. Surely after being with us for so long we should've developed a heirarchy system and the display of dominant/submissive behaviour should only have happened in the early days of his arrival? Obviously I am really confused by this behaviour- people Ive spoken to have never encountered dogs who can "smile"- they presume they are aggressive, which I am sure Dexter is not. I have so many mixed opinions from research that I'm not sure what to think, and I would really appreciate and donations of help towards my problem. For all I know, this behaviour could be quite common and I could be worrying over nothing, but I'll thank you in advance for any advice you may be able to give me. I apologise for my post being so long, but I can't think where else I could contact anyone that may be able to help me. Thank-You, Leanne
Answer:
 thank you for your advice, I shall be taking dexter for his boosters soon so I shall talk to the vet about the anal glands. As for his behaviour, a friend of mine knows of somebody that may be able to come and take a look at him, so hopefully i will know soon. Thank you for your reply, and I shall keep an eye out in the future for what I'm reading on the internet! Leanne
Answer:
 The best thing you can do is to have a good behaviorist evaluate the dog. This could be a sign of stress or something he learned at the former home. I have known dogs that "smiled" without aggression at all - but it can also be a sign of fear. There are a lot of other things I as a behavioral consulatnt would look at in the dog combined with the smiling to help decide if it was benign or the sign of a potential issue. I would be wary until I had a solid evaluation from a professional who is a behaviorist and not a generic trainer. There is just so much subtle body language I want to be able to see along with the smile that a general trainer often misses that a behav or behav cosultant would see and know better how to interpret. As for the butt dragging - I have never in 22 years heard it is a sign of submission. Most often anal sacs, allergies, parasites, infection, growth, etc. It needs to be vet checked to find out what is causing it to be properly dealt with. Even diet can affect anal sacs. Please remember, most of what is out there for dog behavior is based on old and disproven research into wolves that was expanded to dogs. And even that reserach applied to wolves was later found to be incorrect. be careful with what you read and your sources.