The national identity of facial expressions
A Wired Science interview about smiling mentions this interesting study which indicates that it’s easier to identify your fellow countrymen when shown a picture of them smiling than when shown a neutral face:
The findings of this study replicated and extended those of Marsh et al. (2003). Marsh et al. found that the nationality of Japanese and Japanese American individuals was more accurately detected from photographs showing emotional rather than neutral facial expressions. This led them to hypothesize that markers of national identity may be present in even the most basic facial expressions considered to be consistent across cultures. In the present study, perceivers more accurately identified the nationality of Australians and Americans when seen showing an expressions of happiness versus neutral expressions. These findings suggest that the phenomenon of nonverbal accents may generalize across nationalities and emotional expressions.