When an asymmetrical smile is seen, it is very important to consider the emotions being displayed are either a feigned joy-happiness (thus an insincere smile) or contempt (see Body Language and Advertising Secret # 101: Contempt Doesn't Sell). An additional possibility however, is a sincere smile which is being partially suppressed - which is what we see very well exampled here on Matthew McConaughey's face. In this photo he's seen with his fiancee' and Camila Alves. Although the resolution is somewhat low in this image, we can clearly see his bilaterally partially closed eyelids. This dynamic partial closure is required for the smile to be sincere. Additionally though (as pointed out in higher detail in another recent post: Secret # 353: Brad Pitt's Eyes - Sincere and Insincere Smiles), another tell tale signal which must be present for the smile to be sincere, is the concave-up furrows temporarily created in the lower eyelids (seen above on Mr. McConaughey's left eye). If these furrows are NOT seen, even if the eyelids are partially closed - the smile is NOT sincere - and thus it's huge Nonverbal Red Flag signal. But this is certainly not the case here - for Matthew and Camila are now engaged and McConaughey's smile is sincere, just partially suppressed. Congratulations!