Our visual cortexes are wired to quickly recognize faces and then quickly subtract massive amounts of detail from them, zeroing in on their essential message: Is this person happy? Angry? Fearful? Individual faces may vary greatly, but a smirk on one is a lot like a smirk on another. Smirks are conceptual, not pictorial. Our brains are like cartoonists - and cartoonists are like our brains, simplifying and exaggerating, subordinating facial detail to abstract comic concepts.
Jonathan Franzen (2010). “The Discomfort Zone: A Personal History”, p.40, Macmillan