“…My dachshund seems to smile when he is nervous? Do dog’s really smile, and why?”
What kind of smile are you talking about?
There is the classic “pant smile” (a common dog expression during play. Think: tongue out, wide and relaxed parted mouth, most teeth/back teeth showing, mouth loose and upturned into an open “smile” expression while panting with excitement, or happiness).
In this case, it is undeniable that the dog is in a good mood–not just based on his mouth, but his entire body language.
Still, this is not technically a “smile” in the human sense. It does not require the same amount of muscle movement/coordination as a human smile, is not as controlled or complex, and is not used as a primary indicator of the dogs mood (unlike, his tail or stance, for instance).
In fact, open mouth panting may also be a sign of anxiety, hyperactivity/energy, or just being hot. That being said, a clearly happy dog, wearing a clearly happy expression, is certainly using body language to display this happiness in the same way a human uses a smile to display theirs.
Or are you talking about the toothy, goofy, semi-snarl smile a dog makes when he’s nervous, shy, or in trouble? This is actually a sign of submission, or even fear.
- Submissive (or guilty!) “Smile
What’s dangerous about misreading this expression as a “smile” or even an anxious one, is that the submissive “grin” can be hard to distinguish from a full on aggressive snarl.
Submissive / Snarl “Smile” (csindy.com)
Even if a dog is displaying unease via submissive smiling, squinting, ear flattening, etc…he or she could quickly snap, out of fear or distress.
In either of these two above cases, bearing front teeth with a shut, tense jaw, submissive or aggressive stance, and uncomfortable body language are certainly not what we would deem a smile.
Last, there is the elusive “human” or “mimicked smile”–this isn’t one you’ll find much data supporting online, but some dog owners swear on it. 😉 I’ve seen it a few times myself. It’s (what looks like) a smile (of sorts) that dogs express when clearly happy–being pet in the right spot, greeting you when you return home from work–and it looks…well…like a dog attempting to mimic a human smile. Jaw closed, but not tense. Relaxed, but not passive or fearful.
Front to back teeth showing, curving upward like a crooked, kinda creepy human smile. Owners usually claim this is a learned trait…not something they trained the dog to do, or that the dog was born doing… but something he picked up over time. I have no evidence to support this theory. But there clear evidence to prove that dogs did not evolve to smile in this manner and do not do so naturally with other dogs. So. I’ll leave it up to you to decide whether or not this is a smile, a trick, or just a case of a dogs with a funny face.
Last, I think is important to understand when it comes to canine behavior and emotions, is that there has been increasing research and evidence over the past decade indicating just how reactive dogs are to our own expressions. Dogs have co-evolved with humans to such a degree over the last 15,000 years, that not only do they read our expressions from left to right (in the same pattern humans have evolved to read each other’s faces) but they are able to recognize and react to complex facial expressions rapidly in order to assess a human’s mood.
“Now, a new study has found that dogs are able to tell the difference between happy and angry human facial expressions.” (from “Animal Minds” in National Geographic magazine)”
Furthermore, it’s also been proven that our expressions/moods directly impact their behaviors/moods.
So, while a dog smile may not exist in the same sense a human one does, it is safe to say dogs are very aware of what a human smile looks like, what it means, and how it makes them feel. The same can be said about us, viewing them. We might not wiggle our butts or loll our tongues out to express our joy, be we sure as heck know what it means when they do!