All smiles

Real smiles use different muscles when compared with fake smiles, but we're generally rubbish at telling who's putting it on. Real smiles involve a raising of the cheek muscles and a dip in the eyebrow, whereas fake smiles just stretch the corners of the mouth back and don't 'reach the eyes'. It's thought that our general inability to tell real from fake actually helps us to get along, because people can use fake smiles as a sort of social lubricant to make life easier. (Via Brainiac, again.)

Which is interesting enough, but when you put it together with the information that Americans and Brits smile differently, well, you can draw your own conclusions:

While we British smile by pulling our lips back and upwards and exposing our lower teeth, Americans are more likely simply to part their lips and stretch the corners of their mouths. (Via BoingBoing and Neil Gaiman.)

There's also a correlation between how genuine a smiler was at school and how happy they were in later life, with the genuine smilers happier than the fakers. I wonder if there's a correlation between how genuine a celeb is and how they are perceived by the public/how successful they are.

I wish Posh Spice would learn how to smile genuinely. Or just go away completely, actually.