Is this person’s smile genuine or fake?
That is the question on the BBC.co.uk psychology test by Professor Paul Ekman from the University of California. Respondents are finding the test surprisingly difficult when they originally felt confident they could spot a fake.
A lot of test-takers probably are conditioned to see fake smiles during beauty pageants or from over-ambitious cheerleaders, but we are all guilty sometimes!
Another great place to spot extreme-smilers is in advertisements where models or celebrities are forced to smile on cue. Maybe it's not such an easy job after all.
Check out the test yourself here and see how well you do.