Cher Lloyd, on her way to The X Factor's Saturday night live show, waves to some fans and flashes this "False Surprise Smile". Celebrities, Politicians and others in the public eye have a difficult time smiling all the time - and this particular false smile is one of their favorites. The jaw is dropped and the mouth is opened wide - similar to the mouth of surprise. But with true surprise the teeth are rarely exposed. Also, there is no pulling up at the corners of the mouth in surprise as there is when an attempt at a smile is made.
Ms. Lloyd's eyes are opened wider than normal here - again, similar to, but not identical to surprise. The white portions of the eye (sclera) above and below the iris (color part of the eyes) tend not to be exposed with the False-Surprise smile - while the eyes of true surprise are characteristically "white and wide".
Surprise is also the briefest of all emotions. Sincere surprise only lasts for a second or two. In addition, true surprise is very often rapidly followed by fear, laughter, anger or embarrassment. If you witness what you think is surprise - but it keeps on going and going - there is at least an element of exaggeration and drama throw in and perhaps the entire display has been faked.