MissToYouRedux -> UK, US, & OZ - Can you guess the smile? (7/28/2012 1:39:20 PM)
The article gives all the "studies" info. Scroll down for the test images. In brief "look for the lower teeth on smiling British athletes, an agreeable, big smile on Australians, and on the Americans, an assertive, upper-teeth-only smile that gives off a vague air of dominance." [;)]