In this photo, President Obama was giving political support to Jon Corzine in his effort to get re-elected in 2010 as the Governor of New Jersey. Corzine eventually lost to Chris Christie. Contrasting these two men's faces: President Obama has a sincere smile - only his top teeth are visible and he's "smiling with his eyes" nicely. With respect to Barack's eyes, his lower lids bunch-up in a manner highly characteristic with a true, felt smile (Ekman) - whereas Jon Corzine's lids, although partially closed (which is absolutely required in a sincere smile), have a different look to them - there's no "puckering-up" of the lower lid present as is seen on the President's face [this characteristic pucker occurs via the contraction of the orbicularis oculi (pars orbitalis) muscles - which most of the time it is subconsciously stimulated]. Corzine's eyes are being closed with a different muscle however [the orbicularis oculi (pars palpebralis) - when this is used in an attempt to smile - it is consciously controlled] - so they look quite different - and ergo Corzine's smile isn't sincere. In fact, Jon Corzine's "false smile" in this photo indicates bitterness and regret.
Moreover look at Corzine's mouth. The contour of his lips are concave-down, rather than concave up as they should be with any true smile. Of course we all know this without being taught in the first days of our lives - even those who are born blind! Incredible as it seems, virtually everyone who makes a facial expression as Corzine is doing in this image (which occurs very often), believes in the moment, that they are making a slight-to-modest smile. This particular facial expression is one of the most common and demonstrative examples I know of showing the lack of emotional proprioceptive awareness from which most people suffer. It's a very profound disconnect. Most of us aren't really very aware of what our faces and bodies are doing in space and time. This emotional awareness disparity is even wider when the emotions present are negative ones - like anxiety, anger or fear.