"The Japanese men used smiles to cover up their negative expressions much more often than the American men (Ekman, 1972, Friesen, 1972).
To investigate further the meaning of those differences, Matsumoto and Kudoh (1993) obtained ratings from Japanese and Americans on smiling versus non-smiling (i.e., neutral) faces with regard to intelligence, attractiveness, and sociability. Americans rated smiling faces as more intelligent than neutral faces; the Japanese, however, did not. Americans and Japanese both found smiling faces more sociable than neutral faces, but for the Americans the difference was to a greater degree. These differences suggest that cultural display rules cause Japanese and Americans to attribute different meanings to the smile, and serve as a good explanation for perceived major differences in communication styles across cultures."