Dog facial expressions vary quite a bit.
They do smile. The corners of the mouth are pulled upwards like a human smile. I see my pit bull do this all the time when she's obviously happy. It's more noticable when looking at the side of the face or at an angle. The face, especially the corners of the mouth, droop when they are in a neutral or unhappy/sad mood. Of course there is the snarled look with the teeth bared when they are angry enough to fight.
The eyes can change with mental state as well. They can appear bigger brighter when happy or eager. The skin above the eyes will apear wrinkled when they are studying something, are concerned, or worried.
They cant their heads sideways when they are pondering something.
Ears are indicators, too. They will be held aft against the head when they are intimidated/afraid or ready to fight. Perked up when eager or happy, neutral when content.
The few times my pit has gotten into a fight (before it could be stopped) she went from an almost angelic face (for a dog) into a demonic looking beast.
There's also other body indicators like stance, body movement, and tail position/movement.
Dogs are more complex than some give them credit for.
Last edited by Raptor on 11 Nov 2007, 2:36 pm, edited 1 time in total.