This was on digg. I don't think the test is ideal because it's not in context (e.g. someone smiling when nothing funny happened). But I think it's interesting.
http://www.bbc.co.uk/science/humanbo...es/index.shtml

I give a fair amount of credit to someone's smile. It's a good way to tell if they're genuine or not and I think I I'm a good judge.

I got 16/20. 2 of the ones I got wrong are because I leveled myself taking the test (i.e. I thought I had a read).

my results