Melting pot cultures, like Brazil and America's, do not have common ethno-linguistic substrate on which to build civic society. Overt, ostentatious displays of goodwill and trust are a selected-for meme in successful, modern melting-pot cultures.
I predict that smile incidence will vary in correlation to the ethnic homogeneity of a polity.
I predict that smile incidence will vary in correlation to the ethnic homogeneity of a polity.