Via Neil Gaiman, apparently Brits and Americans smile differently. As Robin observed, it's hard to read this article and not "practice" smiling to try to get an idea of what they're talking about. Which I'm afraid I still didn't. When the researcher said "we British smile by pulling our lips back and upwards and exposing our lower teeth," I kept thinking of Nick Park's characters. I don't know too many folks on either side of the pond who expose their lower teeth whilst smiling. Nor, oddly, do I find Angelina Jolie "irresistable," but perhaps that's just me.