I've decided that Australians smile quite differently than Americans. In fact, because they speak so differently, I think their general "mouth gait" (I don't think this is a real expression) is completely different. Australians seem to have a stiffer upper lip and an air about their face that suggests their dialect, whereas Americans have a usually loose upper lip and a different gait that is sometimes mistaken for smugness.
I'm having a tough time putting down on paper my mouth-gait observations, so I shall spend some time reading about FACS to see if I can't describe the differences.
I tested my hypothesis today while looking at people before I heard them spoke. I made accurate predictions most of the time. You're probably thinking, "you're in Australia, if you guess Aussie all the time then you'll most likely succeed." True, but I'm living in a community of about half and half Americans and Australians. Even though all the Americans are all "minorities" it is the Australians who are most friendly towards me. Many of the Yanks socialize in small, closed groups but the Australians are willing to strike up a conversation with me.
Another thing I have noticed is this country's willingness to give out genuine smiles. In the US, when you smile politely at someone, usually they give a "fake" smile back. One of those smiles that's just a flinch of a facial muscle or two, and no eye smile or dimples. You know the kind. They look weird. I don't see them much from Australians -- though this is one device I've been using to figure if someone is a Yank or Aussie.